diff --git a/main/SS/Formula/Eval/FunctionEval.cs b/main/SS/Formula/Eval/FunctionEval.cs
index 6c79df50b..626960612 100644
--- a/main/SS/Formula/Eval/FunctionEval.cs
+++ b/main/SS/Formula/Eval/FunctionEval.cs
@@ -137,14 +137,14 @@ private static Function[] ProduceFunctions()
             retval[37] = new Or(); // OR
             retval[38] = new Not(); // NOT
             retval[39] = NumericFunction.MOD; // MOD
-            retval[40] = new NotImplementedFunction("DCOUNT"); // DCOUNT
-            retval[41] = new NotImplementedFunction("DSUM"); // DSUM
-            retval[42] = new NotImplementedFunction("DAVERAGE"); // DAVERAGE
+            retval[40] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DCOUNT); // DCOUNT
+            retval[41] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DSUM); // DSUM
+            retval[42] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DAVERAGE); // DAVERAGE
             retval[43] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DMIN); // DMIN
-            retval[44] = new NotImplementedFunction("DMAX"); // DMAX
-            retval[45] = new NotImplementedFunction("DSTDEV"); // DSTDEV
+            retval[44] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DMAX);// DMAX
+            retval[45] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DSTDEV); // DSTDEV
             retval[46] = AggregateFunction.VAR; // VAR
-            retval[47] = new NotImplementedFunction("DVAR"); // DVAR
+            retval[47] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DVAR);
             retval[48] = TextFunction.TEXT; // TEXT
             retval[49] = new NotImplementedFunction("LINEST"); // LINEST
             retval[50] = new NotImplementedFunction("TREND"); // TREND
@@ -281,17 +281,17 @@ private static Function[] ProduceFunctions()
             retval[186] = new NotImplementedFunction("GetWORKSPACE"); // GetWORKSPACE
             retval[187] = new NotImplementedFunction("GetWINDOW"); // GetWINDOW
             retval[188] = new NotImplementedFunction("GetDOCUMENT"); // GetDOCUMENT
-            retval[189] = new NotImplementedFunction("DPRODUCT"); // DPRODUCT
+            retval[189] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DPRODUCT);
             retval[190] = LogicalFunction.ISNONTEXT; // IsNONTEXT
             retval[191] = new NotImplementedFunction("GetNOTE"); // GetNOTE
             retval[192] = new NotImplementedFunction("NOTE"); // NOTE
-            retval[193] = new NotImplementedFunction("STDEVP"); // STDEVP
+            retval[193] = AggregateFunction.STDEVP;
             retval[194] = AggregateFunction.VARP; // VARP
-            retval[195] = new NotImplementedFunction("DSTDEVP"); // DSTDEVP
-            retval[196] = new NotImplementedFunction("DVARP"); // DVARP
+            retval[195] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DSTDEVP);
+            retval[196] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DVARP);
             retval[197] = NumericFunction.TRUNC; // TRUNC
             retval[198] = LogicalFunction.ISLOGICAL; // IsLOGICAL
-            retval[199] = new NotImplementedFunction("DCOUNTA"); // DCOUNTA
+            retval[199] = new DStarRunner(DStarRunner.DStarAlgorithmEnum.DCOUNTA);
             retval[200] = new NotImplementedFunction("DELETEBAR"); // DELETEBAR
             retval[201] = new NotImplementedFunction("UNREGISTER"); // UNREGISTER
             retval[204] = NumericFunction.DOLLAR; // USDOLLAR
diff --git a/main/SS/Formula/Functions/DAverage.cs b/main/SS/Formula/Functions/DAverage.cs
new file mode 100644
index 000000000..4756cf10f
--- /dev/null
+++ b/main/SS/Formula/Functions/DAverage.cs
@@ -0,0 +1,63 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+namespace NPOI.SS.Formula.Functions
+{
+    using ExtendedNumerics;
+    using NPOI.SS.Formula.Eval;
+    using System.Numerics;
+
+    /// <summary>
+    /// Implementation of the DAverage function:
+    /// Gets the average value of a column in an area with given conditions.
+    /// </summary>
+    public sealed class DAverage : IDStarAlgorithm
+    {
+        private long count;
+        private double total;
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                count++;
+                total += ((NumericValueEval) eval).NumberValue;
+            }
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                return count == 0 ? NumberEval.ZERO : new NumberEval(GetAverage());
+            }
+        }
+
+        private double GetAverage()
+        {
+            return Divide(total, count);
+        }
+
+        private static double Divide(double total, long count)
+        {
+            return (double) BigDecimal.Divide(new BigDecimal(total), new BigInteger(count));
+        }
+
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
+
+
diff --git a/main/SS/Formula/Functions/DCount.cs b/main/SS/Formula/Functions/DCount.cs
new file mode 100644
index 000000000..518036b31
--- /dev/null
+++ b/main/SS/Formula/Functions/DCount.cs
@@ -0,0 +1,54 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using NPOI.SS.Formula.Eval;
+
+    /// <summary>
+    /// Implementation of the DCount function:
+    /// Counts the number of numeric cells in a column in an area with given conditions.
+    /// </summary>
+    public sealed class DCount : IDStarAlgorithm
+    {
+        private long count;
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                count++;
+            }
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                return new NumberEval(count);
+            }
+        }
+        public bool AllowEmptyMatchField { get; } = true;
+    }
+}
+
diff --git a/main/SS/Formula/Functions/DCountA.cs b/main/SS/Formula/Functions/DCountA.cs
new file mode 100644
index 000000000..ca777d42b
--- /dev/null
+++ b/main/SS/Formula/Functions/DCountA.cs
@@ -0,0 +1,55 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using NPOI.SS.Formula.Eval;
+
+    /// <summary>
+    /// Implementation of the DCountA function:
+    /// Counts the number of non-blank cells in a column in an area with given conditions.
+    /// </summary>
+    public sealed class DCountA : IDStarAlgorithm
+    {
+        private long count;
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(!(eval is BlankEval))
+            {
+                count++;
+            }
+            return true;
+        }
+
+        public ValueEval Result
+        {
+            get
+            {
+                return new NumberEval(count);
+            }
+        }
+        public bool AllowEmptyMatchField { get; } = true;
+    }
+}
+
diff --git a/main/SS/Formula/Functions/DGet.cs b/main/SS/Formula/Functions/DGet.cs
index 25c66546e..dea3e25d2 100644
--- a/main/SS/Formula/Functions/DGet.cs
+++ b/main/SS/Formula/Functions/DGet.cs
@@ -33,14 +33,25 @@ public class DGet : IDStarAlgorithm
 
         public bool ProcessMatch(ValueEval eval)
         {
-            if (result == null) // First match, just Set the value.
+            if(result == null) // First match, just Set the value.
             {
                 result = eval;
             }
             else // There was a previous match, since there is only exactly one allowed, bail out1.
             {
-                result = ErrorEval.NUM_ERROR;
-                return false;
+                if(result is BlankEval)
+                {
+                    result = eval;
+                }
+                else
+                {
+                    // We have a previous filled result.
+                    if(!(eval is BlankEval))
+                    {
+                        result = ErrorEval.NUM_ERROR;
+                        return false;
+                    }
+                }
             }
 
             return true;
@@ -50,17 +61,18 @@ public ValueEval Result
         {
             get
             {
-                if (result == null)
+                if(result == null)
                 {
                     return ErrorEval.VALUE_INVALID;
                 }
-                if (result is BlankEval) {
+                if(result is BlankEval)
+                {
                     return ErrorEval.VALUE_INVALID;
                 }
                 else
                     try
                     {
-                        if (OperandResolver.CoerceValueToString(OperandResolver.GetSingleValue(result, 0, 0)).Equals(""))
+                        if(OperandResolver.CoerceValueToString(OperandResolver.GetSingleValue(result, 0, 0)).Equals(""))
                         {
                             return ErrorEval.VALUE_INVALID;
                         }
@@ -69,12 +81,14 @@ public ValueEval Result
                             return result;
                         }
                     }
-                    catch (EvaluationException e)
+                    catch(EvaluationException e)
                     {
                         return e.GetErrorEval();
                     }
             }
         }
+
+        public bool AllowEmptyMatchField { get; } = false;
     }
 }
 
diff --git a/main/SS/Formula/Functions/DMax.cs b/main/SS/Formula/Functions/DMax.cs
new file mode 100644
index 000000000..88931bd09
--- /dev/null
+++ b/main/SS/Formula/Functions/DMax.cs
@@ -0,0 +1,85 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using NPOI.SS.Formula.Eval;
+
+
+
+
+    /// <summary>
+    /// <para>
+    /// Implementation of the DMax function:
+    /// Finds the maximum value of a column in an area with given conditions.
+    /// </para>
+    /// <para>
+    /// TODO:
+    /// - functions as conditions
+    /// </para>
+    /// </summary>
+    public sealed class DMax : IDStarAlgorithm
+    {
+        private ValueEval maximumValue;
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                if(maximumValue == null)
+                { // First match, just Set the value.
+                    maximumValue = eval;
+                }
+                else
+                { // There was a previous match, find the new minimum.
+                    double currentValue = ((NumericValueEval)eval).NumberValue;
+                    double oldValue = ((NumericValueEval)maximumValue).NumberValue;
+                    if(currentValue > oldValue)
+                    {
+                        maximumValue = eval;
+                    }
+                }
+            }
+
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                if(maximumValue == null)
+                {
+                    return NumberEval.ZERO;
+                }
+                else
+                {
+                    return maximumValue;
+                }
+            }
+            
+        }
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
+
+
diff --git a/main/SS/Formula/Functions/DMin.cs b/main/SS/Formula/Functions/DMin.cs
index b568ca02d..6083d525a 100644
--- a/main/SS/Formula/Functions/DMin.cs
+++ b/main/SS/Formula/Functions/DMin.cs
@@ -67,6 +67,8 @@ public ValueEval Result
                 }
             }
         }
+
+        public bool AllowEmptyMatchField { get; } = false;
     }
 
 }
\ No newline at end of file
diff --git a/main/SS/Formula/Functions/DProduct.cs b/main/SS/Formula/Functions/DProduct.cs
new file mode 100644
index 000000000..c471c4e4f
--- /dev/null
+++ b/main/SS/Formula/Functions/DProduct.cs
@@ -0,0 +1,65 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using NPOI.SS.Formula.Eval;
+
+    /// <summary>
+    /// Implementation of the DProduct function:
+    /// Gets the product value of a column in an area with given conditions.
+    /// </summary>
+    public sealed class DProduct : IDStarAlgorithm
+    {
+        private double product;
+        private bool initDone = false;
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                if(initDone)
+                {
+                    product *= ((NumericValueEval) eval).NumberValue;
+                }
+                else
+                {
+                    product = ((NumericValueEval) eval).NumberValue;
+                    initDone = true;
+                }
+            }
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                return new NumberEval(product);
+            }
+        }
+
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
+
+
diff --git a/main/SS/Formula/Functions/DStarRunner.cs b/main/SS/Formula/Functions/DStarRunner.cs
index 8d39ce165..84d0d0cab 100644
--- a/main/SS/Formula/Functions/DStarRunner.cs
+++ b/main/SS/Formula/Functions/DStarRunner.cs
@@ -18,7 +18,7 @@ limitations under the License.
 namespace NPOI.SS.Formula.Functions
 {
     using System;
-
+    using System.Text.RegularExpressions;
     using NPOI.SS.Formula;
     using NPOI.SS.Formula.Eval;
     using NPOI.SS.Util;
@@ -36,7 +36,16 @@ public enum DStarAlgorithmEnum
         {
             DGET,
             DMIN,
-            // DMAX, // DMAX is not yet implemented
+            DMAX,
+            DSUM,
+            DCOUNT,
+            DCOUNTA,
+            DAVERAGE,
+            DSTDEV,
+            DSTDEVP,
+            DVAR,
+            DVARP,
+            DPRODUCT,
         }
 
         private DStarAlgorithmEnum algoType;
@@ -69,6 +78,50 @@ public ValueEval Evaluate(int srcRowIndex, int srcColumnIndex,
             AreaEval db = (AreaEval)database;
             AreaEval cdb = (AreaEval)conditionDatabase;
 
+            // Create an algorithm runner.
+            IDStarAlgorithm algorithm = null;
+            switch(algoType)
+            {
+                case DStarAlgorithmEnum.DGET:
+                    algorithm = new DGet();
+                    break;
+                case DStarAlgorithmEnum.DMIN:
+                    algorithm = new DMin();
+                    break;
+                case DStarAlgorithmEnum.DMAX:
+                    algorithm = new DMax();
+                    break;
+                case DStarAlgorithmEnum.DSUM:
+                    algorithm = new DSum();
+                    break;
+                case DStarAlgorithmEnum.DCOUNT:
+                    algorithm = new DCount();
+                    break;
+                case DStarAlgorithmEnum.DCOUNTA:
+                    algorithm = new DCountA();
+                    break;
+                case DStarAlgorithmEnum.DAVERAGE:
+                    algorithm = new DAverage();
+                    break;
+                case DStarAlgorithmEnum.DSTDEV:
+                    algorithm = new DStdev();
+                    break;
+                case DStarAlgorithmEnum.DSTDEVP:
+                    algorithm = new DStdevp();
+                    break;
+                case DStarAlgorithmEnum.DVAR:
+                    algorithm = new DVar();
+                    break;
+                case DStarAlgorithmEnum.DVARP:
+                    algorithm = new DVarp();
+                    break;
+                case DStarAlgorithmEnum.DPRODUCT:
+                    algorithm = new DProduct();
+                    break;
+                default:
+                    throw new InvalidOperationException("Unexpected algorithm type " + algoType + " encountered.");
+            }
+
             try
             {
                 filterColumn = OperandResolver.GetSingleValue(filterColumn, srcRowIndex, srcColumnIndex);
@@ -81,26 +134,24 @@ public ValueEval Evaluate(int srcRowIndex, int srcColumnIndex,
             int fc;
             try
             {
-                fc = GetColumnForName(filterColumn, db);
+                if(filterColumn is NumericValueEval)
+                {
+                    //fc is zero based while Excel uses 1 based column numbering
+                    fc = (int) Math.Round(((NumericValueEval) filterColumn).NumberValue) - 1;
+                }
+                else
+                    fc = GetColumnForName(filterColumn, db);
             }
             catch (EvaluationException)
             {
                 return ErrorEval.VALUE_INVALID;
             }
-            if (fc == -1)
+            if (fc == -1 && !algorithm.AllowEmptyMatchField)
             { // column not found
                 return ErrorEval.VALUE_INVALID;
             }
 
-            // Create an algorithm runner.
-            IDStarAlgorithm algorithm = null;
-            switch (algoType)
-            {
-                case DStarAlgorithmEnum.DGET: algorithm = new DGet(); break;
-                case DStarAlgorithmEnum.DMIN: algorithm = new DMin(); break;
-                default:
-                    throw new InvalidOperationException("Unexpected algorithm type " + algoType + " encountered.");
-            }
+            
 
             // Iterate over all db entries.
             int height = db.Height;
@@ -119,6 +170,10 @@ public ValueEval Evaluate(int srcRowIndex, int srcColumnIndex,
                 if (matches)
                 {
                     ValueEval currentValueEval = ResolveReference(db, row, fc);
+                    if(fc < 0 && algorithm.AllowEmptyMatchField && !(currentValueEval is NumericValueEval)) 
+                    {
+                        currentValueEval = NumberEval.ZERO;
+                    }
                     // Pass the match to the algorithm and conditionally abort the search.
                     bool shouldContinue = algorithm.ProcessMatch(currentValueEval);
                     if (!shouldContinue)
@@ -138,7 +193,8 @@ private enum Operator
             largerEqualThan,
             smallerThan,
             smallerEqualThan,
-            equal
+            equal,
+            notEqual,
         }
 
         /**
@@ -179,7 +235,7 @@ private static int GetColumnForString(AreaEval db, String name)
                     continue;
                 }
                 String columnName = OperandResolver.CoerceValueToString(columnNameValueEval);
-                if (name.Equals(columnName))
+                if (name.Equals(columnName, StringComparison.OrdinalIgnoreCase))
                 {
                     resultColumn = column;
                     break;
@@ -278,11 +334,24 @@ private static bool testNormalCondition(ValueEval value, ValueEval condition)
                 if (conditionString.StartsWith("<"))
                 { // It's a </<= condition.
                     String number = conditionString.Substring(1);
-                    if (number.StartsWith("="))
+                    if(number.StartsWith("="))
                     {
                         number = number.Substring(1);
                         return testNumericCondition(value, Operator.smallerEqualThan, number);
                     }
+                    else if(number.StartsWith(">"))
+                    {
+                        number = number.Substring(1);
+                        bool itsANumber = IsNumber(number);
+                        if(itsANumber)
+                        {
+                            return testNumericCondition(value, Operator.notEqual, number);
+                        }
+                        else
+                        {
+                            return testStringCondition(value, Operator.notEqual, number);
+                        }
+                    }
                     else
                     {
                         return testNumericCondition(value, Operator.smallerThan, number);
@@ -310,32 +379,14 @@ private static bool testNormalCondition(ValueEval value, ValueEval condition)
                         return value is BlankEval;
                     }
                     // Distinguish between string and number.
-                    bool itsANumber = false;
-                    try
-                    {
-                        int.Parse(stringOrNumber);
-                        itsANumber = true;
-                    }
-                    catch (FormatException)
-                    { // It's not an int.
-                        try
-                        {
-                            Double.Parse(stringOrNumber);
-                            itsANumber = true;
-                        }
-                        catch (FormatException)
-                        { // It's a string.
-                            itsANumber = false;
-                        }
-                    }
+                    bool itsANumber = IsNumber(stringOrNumber);
                     if (itsANumber)
                     {
                         return testNumericCondition(value, Operator.equal, stringOrNumber);
                     }
                     else
                     { // It's a string.
-                        String valueString = value is BlankEval ? "" : OperandResolver.CoerceValueToString(value);
-                        return stringOrNumber.Equals(valueString);
+                        return testStringCondition(value, Operator.equal, stringOrNumber);
                     }
                 }
                 else
@@ -347,7 +398,17 @@ private static bool testNormalCondition(ValueEval value, ValueEval condition)
                     else
                     {
                         String valueString = value is BlankEval ? "" : OperandResolver.CoerceValueToString(value);
-                        return valueString.StartsWith(conditionString);
+                        String lowerValue = valueString.ToLower(LocaleUtil.GetUserLocale());
+                        String lowerCondition = conditionString.ToLower(LocaleUtil.GetUserLocale());
+                        Regex pattern = Countif.StringMatcher.GetWildCardPattern(lowerCondition);
+                        if(pattern == null)
+                        {
+                            return lowerValue.StartsWith(lowerCondition);
+                        }
+                        else
+                        {
+                            return pattern.IsMatch(lowerValue);
+                        }
                     }
                 }
             }
@@ -423,6 +484,30 @@ private static bool testNumericCondition(
                     return result <= 0;
                 case Operator.equal:
                     return result == 0;
+                case Operator.notEqual:
+                    return result != 0;
+            }
+            return false; // Can not be reached.
+        }
+
+        /**
+         * Test whether a value matches a text condition.
+         * @param valueEval Value to check.
+         * @param op Comparator to use.
+         * @param condition Value to check against.
+         * @return whether the condition holds.
+         */
+        private static bool testStringCondition(
+            ValueEval valueEval, Operator op, String condition)
+        {
+
+            String valueString = valueEval is BlankEval ? "" : OperandResolver.CoerceValueToString(valueEval);
+            switch(op)
+            {
+                case Operator.equal:
+                    return valueString.Equals(condition, StringComparison.OrdinalIgnoreCase);
+                case Operator.notEqual:
+                    return !valueString.Equals(condition, StringComparison.OrdinalIgnoreCase);
             }
             return false; // Can not be reached.
         }
@@ -469,6 +554,36 @@ private static ValueEval ResolveReference(AreaEval db, int dbRow, int dbCol)
                 return e.GetErrorEval();
             }
         }
+
+        /**
+         * Determines whether a given string represents a valid number.
+         *
+         * @param value The string to be checked if it represents a number.
+         * @return {@code true} if the string can be parsed as either an integer or
+         *         a double; {@code false} otherwise.
+         */
+        private static bool IsNumber(String value)
+        {
+            bool itsANumber;
+            try
+            {
+                int.Parse(value);
+                itsANumber = true;
+            }
+            catch(FormatException)
+            { // It's not an int.
+                try
+                {
+                    double.Parse(value);
+                    itsANumber = true;
+                }
+                catch(FormatException)
+                { // It's a string.
+                    itsANumber = false;
+                }
+            }
+            return itsANumber;
+        }
     }
 
 }
\ No newline at end of file
diff --git a/main/SS/Formula/Functions/DStdev.cs b/main/SS/Formula/Functions/DStdev.cs
new file mode 100644
index 000000000..49cac5406
--- /dev/null
+++ b/main/SS/Formula/Functions/DStdev.cs
@@ -0,0 +1,64 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using ExtendedNumerics;
+    using NPOI.SS.Formula.Eval;
+    using NPOI.SS.Util;
+    /// <summary>
+    /// Implementation of the DStdev function:
+    /// Gets the standard deviation value of a column in an area with given conditions.
+    /// </summary>
+    public sealed class DStdev : IDStarAlgorithm
+    {
+        private  List<NumericValueEval> values = new List<NumericValueEval>();
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                values.Add((NumericValueEval) eval);
+            }
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                double[] array = new double[values.Count];
+                int pos = 0;
+                foreach(NumericValueEval d in values)
+                {
+                    array[pos++] = d.NumberValue;
+                }
+                double stdev = StatsLib.stdev(array);
+                return new NumberEval((double) BigDecimal.Parse(NumberToTextConverter.ToText(stdev)));
+
+            }
+        }
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
+
+
diff --git a/main/SS/Formula/Functions/DStdevp.cs b/main/SS/Formula/Functions/DStdevp.cs
new file mode 100644
index 000000000..c951adad7
--- /dev/null
+++ b/main/SS/Formula/Functions/DStdevp.cs
@@ -0,0 +1,63 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using ExtendedNumerics;
+    using NPOI.SS.Formula.Eval;
+    using NPOI.SS.Util;
+    /// <summary>
+    /// Implementation of the DStdevp function:
+    /// Gets the standard deviation value of a column in an area with given conditions.
+    /// </summary>
+    public sealed class DStdevp : IDStarAlgorithm
+    {
+        private  List<NumericValueEval> values = new List<NumericValueEval>();
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                values.Add((NumericValueEval) eval);
+            }
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                double[] array = new double[values.Count];
+                int pos = 0;
+                foreach(NumericValueEval d in values)
+                {
+                    array[pos++] = d.NumberValue;
+                }
+                double stdev = StatsLib.stdevp(array);
+                return new NumberEval((double)BigDecimal.Parse(NumberToTextConverter.ToText(stdev)));
+            }
+            
+        }
+
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
diff --git a/main/SS/Formula/Functions/DSum.cs b/main/SS/Formula/Functions/DSum.cs
new file mode 100644
index 000000000..f6cd3a2c0
--- /dev/null
+++ b/main/SS/Formula/Functions/DSum.cs
@@ -0,0 +1,67 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using NPOI.SS.Formula.Eval;
+
+
+
+
+    /// <summary>
+    /// <para>
+    /// Implementation of the DSum function:
+    /// Finds the total value of matching values in a column in an area with given conditions.
+    /// </para>
+    /// <para>
+    /// TODO:
+    /// - functions as conditions
+    /// </para>
+    /// </summary>
+    public sealed class DSum : IDStarAlgorithm
+    {
+        private double totalValue = 0;
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                double currentValue = ((NumericValueEval)eval).NumberValue;
+                totalValue += currentValue;
+            }
+
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                return new NumberEval(totalValue);
+            }
+        }
+
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
+
+
diff --git a/main/SS/Formula/Functions/DVar.cs b/main/SS/Formula/Functions/DVar.cs
new file mode 100644
index 000000000..6adfe6ac2
--- /dev/null
+++ b/main/SS/Formula/Functions/DVar.cs
@@ -0,0 +1,59 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+using System.Collections.Generic;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using ExtendedNumerics;
+    using NPOI.SS.Formula.Eval;
+    using NPOI.SS.Util;
+    /// <summary>
+    /// Implementation of the DVar function:
+    /// Gets the variance value of a column in an area with given conditions.
+    /// </summary>
+    public sealed class DVar : IDStarAlgorithm
+    {
+        private  List<NumericValueEval> values = new List<NumericValueEval>();
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                values.Add((NumericValueEval) eval);
+            }
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                double[] array = new double[values.Count];
+                int pos = 0;
+                foreach(NumericValueEval d in values)
+                {
+                    array[pos++] = d.NumberValue;
+                }
+                double var = StatsLib.var(array);
+                return new NumberEval((double) BigDecimal.Parse(NumberToTextConverter.ToText(var)));
+            }
+        }
+
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
+
+
diff --git a/main/SS/Formula/Functions/DVarp.cs b/main/SS/Formula/Functions/DVarp.cs
new file mode 100644
index 000000000..0d3921ae1
--- /dev/null
+++ b/main/SS/Formula/Functions/DVarp.cs
@@ -0,0 +1,64 @@
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace NPOI.SS.Formula.Functions
+{
+    using ExtendedNumerics;
+    using NPOI.SS.Formula.Eval;
+    using NPOI.SS.Util;
+    /// <summary>
+    /// Implementation of the DVarp function:
+    /// Gets the variance value of a column in an area with given conditions.
+    /// </summary>
+    public sealed class DVarp : IDStarAlgorithm
+    {
+        private  List<NumericValueEval> values = new List<NumericValueEval>();
+        public bool ProcessMatch(ValueEval eval)
+        {
+            if(eval is NumericValueEval)
+            {
+                values.Add((NumericValueEval) eval);
+            }
+            return true;
+        }
+        public ValueEval Result
+        {
+            get
+            {
+                double[] array = new double[values.Count];
+                int pos = 0;
+                foreach(NumericValueEval d in values)
+                {
+                    array[pos++] = d.NumberValue;
+                }
+                double var = StatsLib.varp(array);
+                return new NumberEval((double)BigDecimal.Parse(NumberToTextConverter.ToText(var)));
+            }
+        }
+
+        public bool AllowEmptyMatchField { get; } = false;
+    }
+}
+
+
diff --git a/main/SS/Formula/Functions/IDStarAlgorithm.cs b/main/SS/Formula/Functions/IDStarAlgorithm.cs
index 84f865c51..25cc3ff48 100644
--- a/main/SS/Formula/Functions/IDStarAlgorithm.cs
+++ b/main/SS/Formula/Functions/IDStarAlgorithm.cs
@@ -39,6 +39,12 @@ public interface IDStarAlgorithm
          * @return a ValueEval
          */
         ValueEval Result { get; }
+        /**
+         * Whether the field value (the 2nd param in DCOUNT, DGET, etc.) can evaluate to empty. It
+         * is allowed to evaluate to empty for DCOUNT.
+         * @return whether the field value can evaluate to empty
+         */
+        bool AllowEmptyMatchField { get; }
     }
 
 }
\ No newline at end of file
diff --git a/testcases/main/SS/Formula/Functions/TestDAverage.cs b/testcases/main/SS/Formula/Functions/TestDAverage.cs
new file mode 100644
index 000000000..f2087a3fb
--- /dev/null
+++ b/testcases/main/SS/Formula/Functions/TestDAverage.cs
@@ -0,0 +1,76 @@
+
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace TestCases.SS.Formula.Functions
+{
+    using NPOI.HSSF.UserModel;
+    using NUnit.Framework;
+    using TestCases.SS.Util;
+
+    /// <summary>
+    /// Testcase for function DAVERAGE()
+    /// </summary>
+    [TestFixture]
+    public class TestDAverage
+    {
+
+        //https://support.microsoft.com/en-us/office/daverage-function-a6a2d5ac-4b4b-48cd-a1d8-7b37834e5aee
+        [Test]
+        public void TestMicrosoftExample1()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1())
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(12) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DAVERAGE(A4:E10, \"Yield\", A1:B2)", 12);
+                Utils.AssertDouble(fe, cell, "DAVERAGE(A4:E10, 3, A4:E10)", 13);
+                Utils.AssertDouble(fe, cell, "DAVERAGE(A4:E10, \"Profit\", A12:A13)", 92.6);
+                Utils.AssertDouble(fe, cell, "DAVERAGE(A4:E10, \"Profit\", B12:C13)", 82.5);
+            }
+        }
+
+        private HSSFWorkbook initWorkbook1()
+        {
+            HSSFWorkbook wb = new HSSFWorkbook();
+            HSSFSheet sheet = wb.CreateSheet() as HSSFSheet;
+            Utils.AddRow(sheet, 0, "Tree", "Height", "Age", "Yield", "Profit", "Height");
+            Utils.AddRow(sheet, 1, "=Apple", ">10", null, null, null, "<16");
+            Utils.AddRow(sheet, 2, "=Pear");
+            Utils.AddRow(sheet, 3, "Tree", "Height", "Age", "Yield", "Profit");
+            Utils.AddRow(sheet, 4, "Apple", 18, 20, 14, 105);
+            Utils.AddRow(sheet, 5, "Pear", 12, 12, 10, 96);
+            Utils.AddRow(sheet, 6, "Cherry", 13, 14, 9, 105);
+            Utils.AddRow(sheet, 7, "Apple", 14, 15, 10, 75);
+            Utils.AddRow(sheet, 8, "Pear", 9, 8, 8, 76.8);
+            Utils.AddRow(sheet, 9, "Apple", 8, 9, 6, 45);
+            Utils.AddRow(sheet, 10);
+            Utils.AddRow(sheet, 11, "Tree", "Height", "Height");
+            Utils.AddRow(sheet, 12, "<>Apple", "<>12", "<>9");
+            return wb;
+        }
+    }
+}
+
+
diff --git a/testcases/main/SS/Formula/Functions/TestDGet.cs b/testcases/main/SS/Formula/Functions/TestDGet.cs
new file mode 100644
index 000000000..1a7f9e78c
--- /dev/null
+++ b/testcases/main/SS/Formula/Functions/TestDGet.cs
@@ -0,0 +1,170 @@
+
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+namespace TestCases.SS.Formula.Functions
+{
+    using NPOI.HSSF.UserModel;
+    using NPOI.SS.UserModel;
+    using NUnit.Framework;
+    using TestCases.SS.Util;
+
+
+    /// <summary>
+    /// Testcase for function DGET()
+    /// </summary>
+    [TestFixture]
+    public class TestDGet
+    {
+
+        //https://support.microsoft.com/en-us/office/dget-function-455568bf-4eef-45f7-90f0-ec250d00892e
+        [Test]
+        public void TestMicrosoftExample1()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(false, "=Apple"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:A3)", FormulaError.NUM);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", 10);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, 4, A1:F3)", 10);
+            }
+        }
+
+        [Test]
+        public void TestMicrosoftExample1CaseInsensitive()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(false, "=apple"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:A3)", FormulaError.NUM);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", 10);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, 4, A1:F3)", 10);
+            }
+        }
+
+        [Test]
+        public void TestMicrosoftExample1StartsWith()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(false, "App"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:A3)", FormulaError.NUM);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", 10);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, 4, A1:F3)", 10);
+            }
+        }
+
+        [Test]
+        public void TestMicrosoftExample1StartsWithLowercase()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(false, "app"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:A3)", FormulaError.NUM);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", 10);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, 4, A1:F3)", 10);
+            }
+        }
+
+        [Test]
+        public void TestMicrosoftExample1Wildcard()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(false, "A*le"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:A3)", FormulaError.NUM);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", 10);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, 4, A1:F3)", 10);
+            }
+        }
+
+        [Test]
+        public void TestMicrosoftExample1WildcardLowercase()
+        {
+            using(HSSFWorkbook wb = initWorkbook1(false, "a*le"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:A3)", FormulaError.NUM);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", 10);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, 4, A1:F3)", 10);
+            }
+        }
+
+        [Test]
+        public void TestMicrosoftExample1AppleWildcardNoMatch()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(false, "A*x"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:A3)", FormulaError.NUM);
+                Utils.AssertError(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", FormulaError.VALUE);
+            }
+        }
+
+        [Test]
+        public void TestMicrosoftExample1Variant()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(true, "=Apple"))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(100) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, \"Yield\", A1:F3)", 6);
+                Utils.AssertDouble(fe, cell, "DGET(A5:E11, 4, A1:F3)", 6);
+            }
+        }
+
+        private HSSFWorkbook initWorkbook1(bool adjustAppleCondition, string appleCondition)
+        {
+            HSSFWorkbook wb = new HSSFWorkbook();
+            HSSFSheet sheet = wb.CreateSheet() as HSSFSheet;
+            Utils.AddRow(sheet, 0, "Tree", "Height", "Age", "Yield", "Profit", "Height");
+            if(adjustAppleCondition)
+            {
+                Utils.AddRow(sheet, 1, appleCondition, ">=8", null, null, null, "<12");
+            }
+            else
+            {
+                Utils.AddRow(sheet, 1, appleCondition, ">10", null, null, null, "<16");
+            }
+            Utils.AddRow(sheet, 2, "Pear", ">12");
+            Utils.AddRow(sheet, 3);
+            Utils.AddRow(sheet, 4, "Tree", "Height", "Age", "Yield", "Profit");
+            Utils.AddRow(sheet, 5, "Apple", 18, 20, 14, 105);
+            Utils.AddRow(sheet, 6, "Pear", 12, 12, 10, 96);
+            Utils.AddRow(sheet, 7, "Cherry", 13, 14, 9, 105);
+            Utils.AddRow(sheet, 8, "Apple", 14, null, 10, 75);
+            Utils.AddRow(sheet, 9, "Pear", 9, 8, 8, 77);
+            Utils.AddRow(sheet, 10, "Apple", 8, 9, 6, 45);
+            return wb;
+        }
+    }
+}
+
diff --git a/testcases/main/SS/Formula/Functions/TestDProduct.cs b/testcases/main/SS/Formula/Functions/TestDProduct.cs
new file mode 100644
index 000000000..692141124
--- /dev/null
+++ b/testcases/main/SS/Formula/Functions/TestDProduct.cs
@@ -0,0 +1,91 @@
+
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+namespace TestCases.SS.Formula.Functions
+{
+    using NPOI.HSSF.UserModel;
+    using NUnit.Framework;
+    using TestCases.SS.Util;
+
+    /// <summary>
+    /// Testcase for function DPRODUCT()
+    /// </summary>
+    [TestFixture]
+    public class TestDProduct
+    {
+
+        //https://support.microsoft.com/en-us/office/dproduct-function-4f96b13e-d49c-47a7-b769-22f6d017cb31
+        [Test]
+        public void TestMicrosoftExample1()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(false))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(12) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DPRODUCT(A5:E11, \"Yield\", A1:F3)", 800, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DPRODUCT(A5:E11, \"Yield\", A13:A14)", 720, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DPRODUCT(A5:E11, \"Yield\", B13:C14)", 7560, 0.0000000001);
+            }
+        }
+
+        [Test]
+        public void TestNoMatch()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1(true))
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(12) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DPRODUCT(A5:E11, \"Yield\", A1:A2)", 0);
+                Utils.AssertDouble(fe, cell, "DPRODUCT(A5:E11, \"Yield\", A1:A3)", 604800);
+            }
+        }
+
+        private HSSFWorkbook initWorkbook1(bool noMatch)
+        {
+            HSSFWorkbook wb = new HSSFWorkbook();
+            HSSFSheet sheet = wb.CreateSheet() as HSSFSheet;
+            Utils.AddRow(sheet, 0, "Tree", "Height", "Age", "Yield", "Profit", "Height");
+            if(noMatch)
+            {
+                Utils.AddRow(sheet, 1, "=NoMatch");
+                Utils.AddRow(sheet, 2);
+            }
+            else
+            {
+                Utils.AddRow(sheet, 1, "=Apple", ">10", null, null, null, "<16");
+                Utils.AddRow(sheet, 2, "=Pear");
+            }
+            Utils.AddRow(sheet, 3);
+            Utils.AddRow(sheet, 4, "Tree", "Height", "Age", "Yield", "Profit");
+            Utils.AddRow(sheet, 5, "Apple", 18, 20, 14, 105);
+            Utils.AddRow(sheet, 6, "Pear", 12, 12, 10, 96);
+            Utils.AddRow(sheet, 7, "Cherry", 13, 14, 9, 105);
+            Utils.AddRow(sheet, 8, "Apple", 14, 15, 10, 75);
+            Utils.AddRow(sheet, 9, "Pear", 9, 8, 8, 77);
+            Utils.AddRow(sheet, 10, "Apple", 8, 9, 6, 45);
+            Utils.AddRow(sheet, 11);
+            Utils.AddRow(sheet, 12, "Tree", "Height", "Height");
+            Utils.AddRow(sheet, 13, "<>Apple", "<>12", "<>9");
+            return wb;
+        }
+    }
+}
+
+
diff --git a/testcases/main/SS/Formula/Functions/TestDStdev.cs b/testcases/main/SS/Formula/Functions/TestDStdev.cs
new file mode 100644
index 000000000..e44036066
--- /dev/null
+++ b/testcases/main/SS/Formula/Functions/TestDStdev.cs
@@ -0,0 +1,84 @@
+
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+namespace TestCases.SS.Formula.Functions
+{
+    using NPOI.HSSF.UserModel;
+    using NUnit.Framework;
+    using TestCases.SS.Util;
+
+    /// <summary>
+    /// Testcase for function DSTDEV() and DSTDEVP()
+    /// </summary>
+    [TestFixture]
+    public class TestDStdev
+    {
+
+        //https://support.microsoft.com/en-us/office/dstdev-function-026b8c73-616d-4b5e-b072-241871c4ab96
+        [Test]
+        public void TestMicrosoftExample1()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1())
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(12) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DSTDEV(A5:E11, \"Yield\", A1:A3)", 2.96647939483827, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DSTDEV(A5:E11, \"Yield\", B12:C14)", 2.66458251889485, 0.0000000001);
+            }
+        }
+
+        //https://support.microsoft.com/en-us/office/dstdevp-function-04b78995-da03-4813-bbd9-d74fd0f5d94b
+        [Test]
+        public void TestDSTDEVPMicrosoftExample1()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1())
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(12) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DSTDEVP(A5:E11, \"Yield\", A1:A3)", 2.65329983228432, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DSTDEVP(A5:E11, \"Yield\", A12:A13)", 0.816496580927726, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DSTDEVP(A5:E11, \"Yield\", B12:C14)", 2.43241991988774, 0.0000000001);
+            }
+        }
+
+        private HSSFWorkbook initWorkbook1()
+        {
+            HSSFWorkbook wb = new HSSFWorkbook();
+            HSSFSheet sheet = wb.CreateSheet() as HSSFSheet;
+            Utils.AddRow(sheet, 0, "Tree", "Height", "Age", "Yield", "Profit", "Height");
+            Utils.AddRow(sheet, 1, "=Apple", ">10", null, null, null, "<16");
+            Utils.AddRow(sheet, 2, "=Pear");
+            Utils.AddRow(sheet, 3);
+            Utils.AddRow(sheet, 4, "Tree", "Height", "Age", "Yield", "Profit");
+            Utils.AddRow(sheet, 5, "Apple", 18, 20, 14, 105);
+            Utils.AddRow(sheet, 6, "Pear", 12, 12, 10, 96);
+            Utils.AddRow(sheet, 7, "Cherry", 13, 14, 9, 105);
+            Utils.AddRow(sheet, 8, "Apple", 14, 15, 10, 75);
+            Utils.AddRow(sheet, 9, "Pear", 9, 8, 8, 77);
+            Utils.AddRow(sheet, 10, "Apple", 8, 9, 6, 45);
+            Utils.AddRow(sheet, 11);
+            Utils.AddRow(sheet, 11, "Tree", "Height", "Height");
+            Utils.AddRow(sheet, 12, "<>Apple", "<>12", "<>9");
+            return wb;
+        }
+    }
+}
+
+
diff --git a/testcases/main/SS/Formula/Functions/TestDVar.cs b/testcases/main/SS/Formula/Functions/TestDVar.cs
new file mode 100644
index 000000000..2aff5f2f2
--- /dev/null
+++ b/testcases/main/SS/Formula/Functions/TestDVar.cs
@@ -0,0 +1,88 @@
+
+/* ====================================================================
+   Licensed to the Apache Software Foundation (ASF) under one or more
+   contributor license agreements.  See the NOTICE file distributed with
+   this work for additional information regarding copyright ownership.
+   The ASF licenses this file to You under the Apache License, Version 2.0
+   (the "License"); you may not use this file except in compliance with
+   the License.  You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+==================================================================== */
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace TestCases.SS.Formula.Functions
+{
+    using NPOI.HSSF.UserModel;
+    using NUnit.Framework;
+    using TestCases.SS.Util;
+
+
+    /// <summary>
+    /// Testcase for function DVAR() and DVARP()
+    /// </summary>
+    [TestFixture]
+    public class TestDVar
+    {
+        //https://support.microsoft.com/en-us/office/dvar-function-d6747ca9-99c7-48bb-996e-9d7af00f3ed1
+        [Test]
+        public void TestMicrosoftExample1()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1())
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(12) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DVAR(A4:E10, \"Yield\", A1:A3)", 8.8, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DVAR(A4:E10, \"Yield\", A12:A13)", 1.0, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DVAR(A4:E10, \"Yield\", B12:C13)", 10.9166666667, 0.0000000001);
+            }
+        }
+
+        //https://support.microsoft.com/en-us/office/dvarp-function-eb0ba387-9cb7-45c8-81e9-0394912502fc
+        [Test]
+        public void TestDVARPMicrosoftExample1()
+        {
+
+            using(HSSFWorkbook wb = initWorkbook1())
+            {
+                HSSFFormulaEvaluator fe = new HSSFFormulaEvaluator(wb);
+                HSSFCell cell = wb.GetSheetAt(0).GetRow(0).CreateCell(12) as HSSFCell;
+                Utils.AssertDouble(fe, cell, "DVARP(A4:E10, \"Yield\", A1:A3)", 7.04, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DVARP(A4:E10, \"Yield\", A12:A13)", 0.666666666666667, 0.0000000001);
+                Utils.AssertDouble(fe, cell, "DVARP(A4:E10, \"Yield\", B12:C13)", 8.1875, 0.0000000001);
+            }
+        }
+
+        private HSSFWorkbook initWorkbook1()
+        {
+            HSSFWorkbook wb = new HSSFWorkbook();
+            HSSFSheet sheet = wb.CreateSheet() as HSSFSheet;
+            Utils.AddRow(sheet, 0, "Tree", "Height", "Age", "Yield", "Profit", "Height");
+            Utils.AddRow(sheet, 1, "=Apple", ">10", null, null, null, "<16");
+            Utils.AddRow(sheet, 2, "=Pear");
+            Utils.AddRow(sheet, 3, "Tree", "Height", "Age", "Yield", "Profit");
+            Utils.AddRow(sheet, 4, "Apple", 18, 20, 14, 105);
+            Utils.AddRow(sheet, 5, "Pear", 12, 12, 10, 96);
+            Utils.AddRow(sheet, 6, "Cherry", 13, 14, 9, 105);
+            Utils.AddRow(sheet, 7, "Apple", 14, 15, 10, 75);
+            Utils.AddRow(sheet, 8, "Pear", 9, 8, 8, 77);
+            Utils.AddRow(sheet, 9, "Apple", 8, 9, 6, 45);
+            Utils.AddRow(sheet, 10);
+            Utils.AddRow(sheet, 11, "Tree", "Height", "Height");
+            Utils.AddRow(sheet, 12, "<>Apple", "<>12", "<>9");
+            return wb;
+        }
+    }
+}
diff --git a/testcases/main/SS/Formula/Functions/TestFrequency.cs b/testcases/main/SS/Formula/Functions/TestFrequency.cs
index b78131d96..8f303c0ca 100644
--- a/testcases/main/SS/Formula/Functions/TestFrequency.cs
+++ b/testcases/main/SS/Formula/Functions/TestFrequency.cs
@@ -21,13 +21,12 @@ limitations under the License.
 using System.IO;
 using System.Text;
 
-namespace NPOI.SS.Formula.Functions
+namespace TestCases.SS.Formula.Functions
 {
     using NPOI.HSSF.UserModel;
     using NPOI.SS.UserModel;
     using NPOI.SS.Util;
     using NPOI.Util;
-    using NPOI.Util.ArrayExtensions;
     using NUnit.Framework;
     using static NPOI.SS.Formula.Functions.Frequency;
 
diff --git a/testcases/main/SS/Util/TestPropertyTemplate.cs b/testcases/main/SS/Util/TestPropertyTemplate.cs
index 50e3e39e7..dca636347 100644
--- a/testcases/main/SS/Util/TestPropertyTemplate.cs
+++ b/testcases/main/SS/Util/TestPropertyTemplate.cs
@@ -22,12 +22,11 @@ limitations under the License.
 using System.IO;
 using System.Text;
 
-namespace NPOI.SS.Util
+namespace TestCases.SS.Util
 {
-
-
     using NPOI.HSSF.UserModel;
     using NPOI.SS.UserModel;
+    using NPOI.SS.Util;
     using NUnit.Framework;
 
     /// <summary>
diff --git a/testcases/test-data/spreadsheet/DStar.xls b/testcases/test-data/spreadsheet/DStar.xls
index 0c8926142..f53e6f6da 100644
Binary files a/testcases/test-data/spreadsheet/DStar.xls and b/testcases/test-data/spreadsheet/DStar.xls differ