Fix: ExcelWorksheets.Delete throws NotSupportedException on ExcelChartsheet (#2367)

The Delete method was attempting to access the PivotTables collection on all worksheet types. However, ExcelChartsheet throws NotSupportedException when accessing PivotTables. Added a type guard to skip PivotTable cleanup for chart sheets.

Co-authored-by: Lieven De Foor <lieven.de.foor@tvh.com>

Author: lievendf

src/EPPlus/ExcelWorksheets.cs

@@ -470,15 +470,18 @@ public void Delete(int Index)
                 worksheet.Drawings.ClearDrawings();
             }
 
-            //Remove all comments
-            if (!(worksheet is ExcelChartsheet) && worksheet.Comments.Count > 0)
+            if (!(worksheet is ExcelChartsheet))
             {
-                worksheet.Comments.Clear();
-            }
+                //Remove all comments
+                if (worksheet.Comments.Count > 0)
+                {
+                    worksheet.Comments.Clear();
+                }
 
-            while(worksheet.PivotTables.Count>0)
-            {
-                worksheet.PivotTables.Delete(worksheet.PivotTables[0]);
+                while (worksheet.PivotTables.Count > 0)
+                {
+                    worksheet.PivotTables.Delete(worksheet.PivotTables[0]);
+                }
             }
             //Delete any parts still with relations to the Worksheet.
             DeleteRelationsAndParts(worksheet.Part);

src/EPPlusTest/Issues/ChartSheetDeleteTests.cs

@@ -0,0 +1,35 @@
+/*******************************************************************************
+ * Required Notice: Copyright (C) EPPlus Software AB. 
+ * https://epplussoftware.com
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *******************************************************************************/
+using System;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using OfficeOpenXml;
+using OfficeOpenXml.Drawing.Chart;
+
+namespace EPPlusTest.Issues
+{
+    [TestClass]
+    public class ChartSheetDeleteTests
+    {
+        [TestMethod]
+        public void DeleteChartSheetShouldNotThrowNotSupportedException()
+        {
+            using (var package = new ExcelPackage())
+            {
+                var ws = package.Workbook.Worksheets.Add("Data");
+                var chartSheet = package.Workbook.Worksheets.AddChart("ChartSheet", eChartType.ColumnClustered);
+                
+                // This call previously threw NotSupportedException because it tried to access chartSheet.PivotTables
+                package.Workbook.Worksheets.Delete(chartSheet);
+                
+                Assert.AreEqual(1, package.Workbook.Worksheets.Count);
+            }
+        }
+    }
+}