Revert "Refactor TreeView drag-and-drop and improve tests"

This reverts commit 81235e9.

# Conflicts:
#	src/BootstrapBlazor/Components/TreeView/TreeView.razor.cs

Author: ArgoZhang

src/BootstrapBlazor/Components/TreeView/TreeView.razor.cs

@@ -818,8 +818,11 @@ private async Task OnItemDrop(TreeDropEventArgs<TItem> e)
                     }
 
                     break;
+                default:
+                    throw new ArgumentOutOfRangeException();
             }
 
+
             _draggingItem = null;
             _previewDrop = false;
             _rows = GetTreeItems().ToFlat();
@@ -893,4 +896,5 @@ public class TreeDropEventArgs<TItem>
     /// Gets or sets whether to expand the source item's children when dropping.
     /// </summary>
     public bool ExpandAfterDrop { get; set; }
+
 }

src/BootstrapBlazor/Components/TreeView/TreeViewRow.razor.cs

@@ -326,8 +326,8 @@ private async Task ClickRow()
     /// <summary>
     /// Triggered when an item is dropped
     /// </summary>
-    [Parameter][Required]
-    public Func<TreeDropEventArgs<TItem>, Task> OnItemDrop { get; set; } = null!;
+    [Parameter]
+    public Func<TreeDropEventArgs<TItem>, Task>? OnItemDrop { get; set; }
 
     private async Task DragStart(DragEventArgs e)
     {
@@ -336,6 +336,7 @@ private async Task DragStart(DragEventArgs e)
         {
             _expandAfterDrop = true;
             await ToggleNodeAsync();
+            StateHasChanged();
         }else
         {
             _expandAfterDrop = false;
@@ -388,6 +389,10 @@ private void DragLeaveChildBelow(DragEventArgs e)
 
     private async Task DropChildInside(DragEventArgs e)
     {
+        if (OnItemDrop is null)
+        {
+            return;
+        }
         _previewChildFirst = false;
         _previewChildLast = false;
         _previewBelow = false;
@@ -404,6 +409,10 @@ private async Task DropChildInside(DragEventArgs e)
 
     private async Task DropChildBelow(DragEventArgs e)
     {
+        if (OnItemDrop is null)
+        {
+            return;
+        }
         _previewChildFirst = false;
         _previewChildLast = false;
         _previewBelow = false;

test/UnitTest/Components/TreeViewTest.cs

@@ -1304,30 +1304,6 @@ public async Task Draggable_Basic_MoveAsSiblingBelow()
         Assert.Equal("Child1", parent.Items[1].Text);
     }
 
-    [Fact]
-    public async Task Draggable_NothingDrop()
-    {
-        var items = new List<TreeFoo>
-        {
-            new() { Text = "Root1", Id = "1" },
-            new() { Text = "Child1", Id = "2", ParentId = "1" }
-        };
-
-        var nodes = TreeFoo.CascadingTree(items);
-        nodes[0].IsExpand = true;
-        var cut = Context.RenderComponent<TreeView<TreeFoo>>(pb =>
-        {
-            pb.Add(a => a.Items, nodes);
-            pb.Add(a => a.ItemDraggable, true);
-        });
-
-        var rows = cut.FindComponents<TreeViewRow<TreeFoo>>();
-        var dropTarget = rows[1]; // Child1
-        var targetDropZone = dropTarget.Find(".tree-drop-child-below");
-
-        await Assert.ThrowsAsync<InvalidOperationException>(() => targetDropZone.TriggerEventAsync("ondrop", new DragEventArgs()));
-    }
-
     [Fact]
     public async Task Draggable_OnDrop_Cancel()
     {
@@ -1385,6 +1361,7 @@ public async Task Draggable_DragClassState()
         });
 
         var row = cut.FindComponent<TreeViewRow<TreeFoo>>();
+        var dragEvent = new DragEventArgs();
 
         // 获取可拖拽的 DOM 元素
         var dragSourceElement = row.Find(".tree-node");
@@ -1396,18 +1373,6 @@ public async Task Draggable_DragClassState()
         // 触发拖拽结束
         await dragSourceElement.TriggerEventAsync("ondragend", new DragEventArgs());
         Assert.DoesNotContain("tree-drop-pass", row.Markup);
-
-        var dropBelow = cut.Find(".tree-drop-child-below");
-        await dropBelow.TriggerEventAsync("ondragenter", new DragEventArgs());
-        Assert.Contains("tree-preview-below", cut.Markup); // 检查是否有拖拽进入的样式
-        await dropBelow.TriggerEventAsync("ondragleave", new DragEventArgs());
-        Assert.DoesNotContain("tree-preview-below", cut.Markup); // 检查是否移除拖拽进入的样式
-
-        var dropInside = cut.Find(".tree-drop-child-inside");
-        await dropInside.TriggerEventAsync("ondragenter", new DragEventArgs());
-        Assert.Contains("tree-preview-child-last", cut.Markup); // 检查是否有拖拽进入的样式
-        await dropInside.TriggerEventAsync("ondragleave", new DragEventArgs());
-        Assert.DoesNotContain("tree-preview-child-last", cut.Markup); // 检查是否移除拖拽进入的样式
     }
 
     class MockTree<TItem> : TreeView<TItem> where TItem : class