diff --git a/src/BootstrapBlazor/Extensions/TreeItemExtensions.cs b/src/BootstrapBlazor/Extensions/TreeItemExtensions.cs
index 802e7368a7997c8e3ad1bd9a74942a4287a86b3a..626a662dd95269135aa37dcf213e4423e1460955 100644
--- a/src/BootstrapBlazor/Extensions/TreeItemExtensions.cs
+++ b/src/BootstrapBlazor/Extensions/TreeItemExtensions.cs
@@ -35,7 +35,8 @@ public static class TreeItemExtensions
     /// <returns></returns>
     public static IEnumerable<TreeViewItem<TItem>> GetAllItems<TItem>(this IEnumerable<TreeViewItem<TItem>> source)
     {
-        return GetAllSubItems(source).Append(source.First());
+        //return GetAllSubItems(source).Append(source.First());
+        return GetAllSubItems(source).Union(source);
     }
 
     /// <summary>
diff --git a/test/UnitTest/Extensions/TreeItemExtensionsTest.cs b/test/UnitTest/Extensions/TreeItemExtensionsTest.cs
new file mode 100644
index 0000000000000000000000000000000000000000..b8b9e7a8299461acfc7718778ec2f7f6a45851ef
--- /dev/null
+++ b/test/UnitTest/Extensions/TreeItemExtensionsTest.cs
@@ -0,0 +1,74 @@
+// Copyright (c) Argo Zhang (argo@163.com). All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+// Website: https://www.blazor.zone or https://argozhang.github.io/
+
+using System.Diagnostics;
+
+namespace UnitTest.Extensions;
+
+public class TreeItemExtensionsTest
+{
+
+    /// <summary>
+    /// 单一顶级树节点
+    /// </summary>
+    [Fact]
+    public async Task 单一顶级树节点()
+    {
+        //GetAllItems存在错误。
+        var sourceItems = new List<TreeViewItem<string>>()
+        {
+            new TreeViewItem<string>("01")
+            {
+                Text="01",Items = new List<TreeViewItem<string>>()
+                {
+                    new TreeViewItem<string>("0101") { Text="0101" },
+                    new TreeViewItem<string>("0102") { Text="0102" },
+                }
+            }
+        };
+
+        var items = sourceItems.GetAllItems();
+        var list = items.Select(x => x.Text ?? "").ToList();
+
+        Assert.True(items.Count() == 3);
+
+        await Task.CompletedTask;
+    }
+
+
+    /// <summary>
+    /// 多顶级树节点
+    /// </summary>
+    [Fact]
+    public async Task 多顶级树节点()
+    {
+        //GetAllItems存在错误。
+        var sourceItems = new List<TreeViewItem<string>>()
+        {
+            new TreeViewItem<string>("01")
+            {
+                Text="01",Items = new List<TreeViewItem<string>>()
+                {
+                    new TreeViewItem<string>("0101") { Text="0101" },
+                    new TreeViewItem<string>("0102") { Text="0102" },
+                }
+            },
+            new TreeViewItem<string>("02")
+            {
+                Text="02",Items = new List<TreeViewItem<string>>()
+                {
+                    new TreeViewItem<string>("0201") { Text="0201" },
+                    new TreeViewItem<string>("0202") { Text="0202" },
+                }
+            },
+        };
+
+        var items = sourceItems.GetAllItems();
+        var list = items.Select(x => x.Text ?? "").ToList();
+
+        Assert.True(items.Count() == 6);
+
+        await Task.CompletedTask;
+    }
+}