Fix delete and add chart throws exception

ooxml/XSSF/UserModel/XSSFDrawing.cs

@@ -26,7 +26,8 @@ limitations under the License.
 using NPOI.OpenXmlFormats.Dml;
 using NPOI.SS.Util;
 using NPOI.Util;
-
+using System.Text.RegularExpressions;
+using System.Linq;
 
 namespace NPOI.XSSF.UserModel
 {
@@ -170,8 +171,7 @@ public IPicture CreatePicture(IClientAnchor anchor, int pictureIndex)
         /// <returns>the newly created chart</returns>
         public IChart CreateChart(IClientAnchor anchor)
         {
-            int chartNumber = GetPackagePart().Package.
-                GetPartsByContentType(XSSFRelation.CHART.ContentType).Count + 1;
+            int chartNumber = GetNewChartNumber();
 
             RelationPart rp = CreateRelationship(
             XSSFRelation.CHART, XSSFFactory.GetInstance(), chartNumber, false);
@@ -184,6 +184,54 @@ public IChart CreateChart(IClientAnchor anchor)
             return chart;
         }
 
+        /// <summary>
+        /// Removes chart.
+        /// </summary>
+        /// <param name="chart">The chart to be removed.</param>
+        public void RemoveChart(XSSFChart chart)
+        {
+            CT_Drawing ctDrawing = GetCTDrawing();
+            XSSFGraphicFrame frame = chart.GetGraphicFrame();
+            CT_GraphicalObjectFrame internalFrame = frame.GetCTGraphicalObjectFrame();
+            int anchorIndex = ctDrawing.CellAnchors.FindIndex(anchor => anchor.graphicFrame == internalFrame);
+
+            if (anchorIndex != -1)
+            {
+                ctDrawing.CellAnchors.RemoveAt(anchorIndex);
+
+                foreach (var part in GetRelations().Where(part => part is XSSFChart && part == chart))
+                {
+                    RemoveRelation(part);
+                }
+            }
+        }
+
+        private int GetNewChartNumber()
+        {
+            List<PackagePart> existingCharts = GetPackagePart().Package.
+                GetPartsByContentType(XSSFRelation.CHART.ContentType);
+            HashSet<int> numbers = new HashSet<int>();
+
+            foreach (PackagePart chart in existingCharts)
+            {
+                var match = Regex.Match(chart.PartName.Name, @"\d+");
+
+                if (match.Success)
+                {
+                    numbers.Add(int.Parse(match.Value));
+                }
+            }
+
+            var newChartNumber = 1;
+
+            while (numbers.Contains(newChartNumber))
+            {
+                newChartNumber++;
+            }
+
+            return newChartNumber;
+        }
+
         //public XSSFChart CreateChart(IClientAnchor anchor)
         //{
         //    return CreateChart((XSSFClientAnchor)anchor);

testcases/ooxml/XSSF/UserModel/TestXSSFChart.cs

@@ -21,6 +21,8 @@ limitations under the License.
 using NPOI.SS.UserModel.Charts;
 using NPOI.XSSF.UserModel;
 using NPOI.XSSF;
+using NPOI.OpenXmlFormats.Dml.Spreadsheet;
+using System.Linq;
 
 namespace TestCases.XSSF.UserModel
 {
@@ -66,6 +68,7 @@ public void TestGetCharts()
 
             Assert.IsNotNull(XSSFTestDataSamples.WriteOutAndReadBack(wb));
         }
+
         [Test]
         public void TestAddChartsToNewWorkbook()
         {
@@ -88,6 +91,47 @@ public void TestAddChartsToNewWorkbook()
             Assert.IsNotNull(XSSFTestDataSamples.WriteOutAndReadBack(wb));
         }
 
+        [Test]
+        public void TestRemoveChart()
+        {
+            XSSFWorkbook workbook = new XSSFWorkbook();
+            XSSFSheet sheet = (XSSFSheet)workbook.CreateSheet();
+            XSSFDrawing drawingPatriarch = (XSSFDrawing)sheet.CreateDrawingPatriarch();
+            XSSFClientAnchor anchor1 = new XSSFClientAnchor(0, 0, 0, 0, 1, 1, 10, 30);
+            XSSFChart chart = (XSSFChart)drawingPatriarch.CreateChart(anchor1);
+            XSSFClientAnchor anchor2 = new XSSFClientAnchor(0, 0, 0, 0, 1, 11, 10, 60);
+            _ = (XSSFChart)drawingPatriarch.CreateChart(anchor2);
+
+            Assert.AreEqual(2, drawingPatriarch.GetCharts().Count);
+
+            drawingPatriarch.RemoveChart(chart);
+
+            Assert.AreEqual(1, drawingPatriarch.GetCharts().Count);
+        }
+
+        [Test]
+        public void TestRemoveOneOfTwoChartsAndAddNewOne()
+        {
+            XSSFWorkbook workbook = new XSSFWorkbook();
+            XSSFSheet sheet = (XSSFSheet)workbook.CreateSheet();
+            XSSFDrawing drawingPatriarch = (XSSFDrawing)sheet.CreateDrawingPatriarch();
+            XSSFClientAnchor anchor1 = new XSSFClientAnchor(0, 0, 0, 0, 1, 1, 10, 30);
+            XSSFChart chart = (XSSFChart)drawingPatriarch.CreateChart(anchor1);
+            XSSFClientAnchor anchor2 = new XSSFClientAnchor(0, 0, 0, 0, 1, 11, 10, 60);
+            _ = (XSSFChart)drawingPatriarch.CreateChart(anchor2);
+
+            Assert.AreEqual(2, drawingPatriarch.GetCharts().Count);
+
+            drawingPatriarch.RemoveChart(chart);
+
+            Assert.AreEqual(1, drawingPatriarch.GetCharts().Count);
+
+            XSSFClientAnchor a3 = new XSSFClientAnchor(0, 0, 0, 0, 1, 111, 10, 90);
+            _ = (XSSFChart)drawingPatriarch.CreateChart(a3);
+
+            Assert.AreEqual(2, drawingPatriarch.GetCharts().Count);
+        }
+
         [Test]
         public void TestGetChartAxisBug57362()
         {