From da97026edbcf4894bf30dc806cbaeac52e243ca9 Mon Sep 17 00:00:00 2001
From: shixia <a3190778733@gmail.com>
Date: Mon, 24 Aug 2026 08:49:33 +0800
Subject: [PATCH 1/2] Add new function: UnmergeCell

---
 Excelize.Tests/UnitTest.cs | 23 ++++++++++++++++++++++
 Excelize/Excelize.cs       | 39 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/Excelize.Tests/UnitTest.cs b/Excelize.Tests/UnitTest.cs
index c22f5c0..99b112c 100644
--- a/Excelize.Tests/UnitTest.cs
+++ b/Excelize.Tests/UnitTest.cs
@@ -93,7 +93,22 @@ public void TestAddChart()
         Assert.Null(Record.Exception(() => f.SaveAs("TestAddChart.xlsx")));
         Assert.Empty(f.Close());
     }
+    [Fact]
+    public void TestMergeCell()
+    {
+        // 创建一个新的 Excel 文件
+        File f = Excelize.NewFile();
+
+        // 合并 Sheet1 的 D3 到 E9
+        Assert.Null(
+            Record.Exception(() =>
+                f.MergeCell("Sheet1", "D3", "E9")
+            )
+        );
 
+        // 关闭文件
+        Assert.Empty(f.Close());
+    }
     [Fact]
     public void TestAddComment()
     {
@@ -977,6 +992,14 @@ public void TestMergeCells()
         );
         RuntimeError err = Assert.Throws<RuntimeError>(() => f.MergeCell("SheetN", "A1", "B2"));
         Assert.Equal("sheet SheetN does not exist", err.Message);
+        Assert.Null(
+            Record.Exception(() =>
+            {
+                f.UnmergeCell("Sheet1", "D3", "E9");
+            })
+        );
+        err = Assert.Throws<RuntimeError>(() => f.UnmergeCell("SheetN", "A1", "B2"));
+        Assert.Equal("sheet SheetN does not exist", err.Message);
         Assert.Null(Record.Exception(() => f.SaveAs("TestMergeCells.xlsx")));
         Assert.Empty(f.Close());
     }
diff --git a/Excelize/Excelize.cs b/Excelize/Excelize.cs
index b907571..46c7208 100644
--- a/Excelize/Excelize.cs
+++ b/Excelize/Excelize.cs
@@ -421,6 +421,14 @@ internal static extern IntPtr MergeCell(
             [MarshalAs(UnmanagedType.LPUTF8Str)] string bottomRightCell
         );
 
+        [DllImport(LibraryName, CallingConvention = CallingConvention.Cdecl)]
+        internal static extern IntPtr UnmergeCell(
+            long fileIdx,
+            [MarshalAs(UnmanagedType.LPUTF8Str)] string sheet,
+            [MarshalAs(UnmanagedType.LPUTF8Str)] string topLeftCell,
+            [MarshalAs(UnmanagedType.LPUTF8Str)] string bottomRightCell
+        );
+
         [DllImport(LibraryName, CallingConvention = CallingConvention.Cdecl)]
         internal static extern IntPtr MoveSheet(
             long fileIdx,
@@ -6338,6 +6346,37 @@ public void UngroupSheets()
                 throw new RuntimeError(err);
         }
 
+        /// <summary>
+        /// UnmergeCell provides a function to unmerge a given range reference.
+        /// <example>
+        /// For example unmerge range reference D3:E9 on Sheet1:
+        /// <code>
+        /// try
+        /// {
+        ///     f.UnmergeCell("Sheet1", "D3", "E9");
+        /// }
+        /// catch (RuntimeError err)
+        /// {
+        ///     Console.WriteLine(err.Message);
+        /// }
+        /// </code>
+        /// </example>
+        /// </summary>
+        /// <param name="sheet">The worksheet name</param>
+        /// <param name="topLeftCell">The top-left cell reference</param>
+        /// <param name="bottomRightCell">The bottom-right cell reference</param>
+        /// <remarks>Attention: overlapped range will also be unmerged</remarks>
+        /// <exception cref="RuntimeError">Return None if no error occurred,
+        /// otherwise raise a RuntimeError with the message.</exception>
+        public void UnmergeCell(string sheet, string topLeftCell, string bottomRightCell)
+        {
+            string err = Marshal.PtrToStringUTF8(
+                Lib.UnmergeCell(FileIdx, sheet, topLeftCell, bottomRightCell)
+            );
+            if (!string.IsNullOrEmpty(err))
+                throw new RuntimeError(err);
+        }
+
         /// <summary>
         /// UnsetConditionalFormat provides a function to unset the conditional
         /// format by given worksheet name and range reference.

From 52836a439856ee1a6c7d4e4b0e4a6bdc2ffb04ec Mon Sep 17 00:00:00 2001
From: shixia <a3190778733@gmail.com>
Date: Mon, 24 Aug 2026 08:54:05 +0800
Subject: [PATCH 2/2] Remove unuse testcase

---
 Excelize.Tests/UnitTest.cs | 15 ---------------
 1 file changed, 15 deletions(-)

diff --git a/Excelize.Tests/UnitTest.cs b/Excelize.Tests/UnitTest.cs
index 99b112c..c2371bc 100644
--- a/Excelize.Tests/UnitTest.cs
+++ b/Excelize.Tests/UnitTest.cs
@@ -93,22 +93,7 @@ public void TestAddChart()
         Assert.Null(Record.Exception(() => f.SaveAs("TestAddChart.xlsx")));
         Assert.Empty(f.Close());
     }
-    [Fact]
-    public void TestMergeCell()
-    {
-        // 创建一个新的 Excel 文件
-        File f = Excelize.NewFile();
-
-        // 合并 Sheet1 的 D3 到 E9
-        Assert.Null(
-            Record.Exception(() =>
-                f.MergeCell("Sheet1", "D3", "E9")
-            )
-        );
 
-        // 关闭文件
-        Assert.Empty(f.Close());
-    }
     [Fact]
     public void TestAddComment()
     {