Fix IndexOutOfRangeException in LoadFromText with trailing columns (#2388)

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

Author: lievendf

src/EPPlus/LoadFunctions/LoadFromTextBase.cs

@@ -62,16 +62,18 @@ protected bool IsEOL(string text, int ix, string eol)
 
         protected object ConvertData(T Format, eDataTypes[] dataType, string v, int col, bool isText)
         {
-            if (isText && (dataType == null || dataType.Length < col))
-            {
-                return string.IsNullOrEmpty(v) ? null : v;
-            }
-            else
+            bool isOutOfBounds = dataType == null || col >= dataType.Length;
+
+            if (isOutOfBounds)
             {
-                if(dataType == null || dataType.Length < col)
-                    return ConvertData(Format, eDataTypes.Unknown, v, col, isText);
-                return ConvertData(Format, dataType[col], v, col, isText);
+                if (isText)
+                {
+                    return string.IsNullOrEmpty(v) ? null : v;
+                }
+                return ConvertData(Format, eDataTypes.Unknown, v, col, isText);
             }
+
+            return ConvertData(Format, dataType[col], v, col, isText);
         }
 
         protected object ConvertData(T Format, eDataTypes? dataType, string v, int col, bool isText)

src/EPPlusTest/LoadFunctions/LoadFromTextTests.cs

@@ -467,5 +467,21 @@ public void ReadFixedTextFile3()
             }
         }
 
+        [TestMethod]
+        public void ShouldLoadCsvFormatWithTrailingColumns()
+        {
+            // This test verifies that importing a text/CSV file with more columns than specified in DataTypes does not crash.
+            // Previously, an off-by-one bounds check (dataType.Length < col) allowed the loop to attempt accessing dataType[col]
+            // when 'col' was equal to 'dataType.Length', resulting in a System.IndexOutOfRangeException.
+            // With the fix (col >= dataType.Length), trailing columns beyond the DataTypes array are gracefully imported as Unknown (General).
+            AddLine("a;2;extra");
+            _format.Delimiter = ';';
+            _format.DataTypes = new eDataTypes[] { eDataTypes.String, eDataTypes.Number };
+            _worksheet.Cells["A1"].LoadFromText(_lines.ToString(), _format);
+            Assert.AreEqual("a", _worksheet.Cells["A1"].Value);
+            Assert.AreEqual(2d, _worksheet.Cells["B1"].Value);
+            Assert.AreEqual("extra", _worksheet.Cells["C1"].Value);
+        }
+
     }
 }