AVRO-3490 Updated to use throw expressions

lang/csharp/src/apache/main/Schema/ArraySchema.cs

@@ -66,8 +66,7 @@ public static ArraySchema Create(Schema items, PropertyMap customAttributes = nu
         private ArraySchema(Schema items, PropertyMap customAttributes)
             : base(Type.Array, customAttributes)
         {
-            if (null == items) throw new ArgumentNullException(nameof(items));
-            this.ItemSchema = items;
+            ItemSchema = items ?? throw new ArgumentNullException(nameof(items));
         }
 
         /// <summary>

lang/csharp/src/apache/main/Schema/Field.cs

@@ -138,12 +138,7 @@ internal Field ChangePosition(int newPosition)
         }
 
         /// <summary>
-        /// A flag to indicate if reader schema has a field that is missing from writer schema and has a default value
-        /// This is set in CanRead() which is always be called before deserializing data
-        /// </summary>
-
-        /// <summary>
-        /// Constructor for the field class
+        /// Initializes a new instance of the <see cref="Field"/> class.
         /// </summary>
         /// <param name="schema">schema for the field type</param>
         /// <param name="name">name of the field</param>
@@ -153,21 +148,29 @@ internal Field ChangePosition(int newPosition)
         /// <param name="defaultValue">field's default value if it exists</param>
         /// <param name="sortorder">sort order of the field</param>
         /// <param name="props">dictionary that provides access to custom properties</param>
+        /// <exception cref="ArgumentNullException">
+        /// name - name cannot be null.
+        /// or
+        /// type - type cannot be null.
+        /// </exception>
         internal Field(Schema schema, string name, IList<string> aliases, int pos, string doc,
                         JToken defaultValue, SortOrder sortorder, PropertyMap props)
         {
-            if (string.IsNullOrEmpty(name)) throw new ArgumentNullException(nameof(name), "name cannot be null.");
-            if (null == schema) throw new ArgumentNullException("type", "type cannot be null.");
-            this.Schema = schema;
-            this.Name = name;
+            if (string.IsNullOrEmpty(name))
+            {
+                throw new ArgumentNullException(nameof(name), "name cannot be null.");
+            }
+
+            Schema = schema ?? throw new ArgumentNullException("type", "type cannot be null.");
+            Name = name;
 #pragma warning disable CS0618 // Type or member is obsolete
             this.aliases = aliases;
 #pragma warning restore CS0618 // Type or member is obsolete
-            this.Pos = pos;
-            this.Documentation = doc;
-            this.DefaultValue = defaultValue;
-            this.Ordering = sortorder;
-            this.Props = props;
+            Pos = pos;
+            Documentation = doc;
+            DefaultValue = defaultValue;
+            Ordering = sortorder;
+            Props = props;
         }
 
         /// <summary>

lang/csharp/src/apache/main/Schema/LogicalSchema.cs

@@ -52,8 +52,7 @@ internal static LogicalSchema NewInstance(JToken jtok, PropertyMap props, Schema
 
         private LogicalSchema(Schema baseSchema, string logicalTypeName,  PropertyMap props) : base(Type.Logical, props)
         {
-            if (null == baseSchema) throw new ArgumentNullException(nameof(baseSchema));
-            BaseSchema = baseSchema;
+            BaseSchema = baseSchema ?? throw new ArgumentNullException(nameof(baseSchema));
             LogicalTypeName = logicalTypeName;
             LogicalType = LogicalTypeFactory.Instance.GetFromLogicalSchema(this);
         }

lang/csharp/src/apache/main/Schema/MapSchema.cs

@@ -73,8 +73,7 @@ internal static MapSchema NewInstance(JToken jtok, PropertyMap props, SchemaName
         private MapSchema(Schema valueSchema, PropertyMap cutsomProperties)
             : base(Type.Map, cutsomProperties)
         {
-            if (null == valueSchema) throw new ArgumentNullException(nameof(valueSchema), "valueSchema cannot be null.");
-            this.ValueSchema = valueSchema;
+            ValueSchema = valueSchema ?? throw new ArgumentNullException(nameof(valueSchema), "valueSchema cannot be null.");
         }
 
         /// <summary>