Refactor TreeView drag-and-drop and improve tests

Refactored TreeView and TreeViewRow to require OnItemDrop and remove null checks, simplifying drag-and-drop logic. Updated tests to cover cases where OnItemDrop is not set and to verify drag-and-drop visual feedback.

Author: syminomega

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

@@ -380,7 +380,8 @@ protected override async Task OnAfterRenderAsync(bool firstRender)
     /// <inheritdoc/>
     /// </summary>
     /// <returns></returns>
-    protected override Task InvokeInitAsync() => InvokeVoidAsync("init", Id, new { Invoke = Interop, Method = nameof(TriggerKeyDown) });
+    protected override Task InvokeInitAsync() =>
+        InvokeVoidAsync("init", Id, new { Invoke = Interop, Method = nameof(TriggerKeyDown) });
 
     private bool _keyboardArrowUpDownTrigger;
 
@@ -730,7 +731,6 @@ public void ClearCheckedItems()
 
     #region Draggable
 
-
     /// <summary>
     /// Gets or sets whether to enable item dragging. Default is false.
     /// </summary>
@@ -831,11 +831,8 @@ private async Task OnItemDrop(TreeDropEventArgs<TItem> e)
                     }
 
                     break;
-                default:
-                    throw new ArgumentOutOfRangeException();
             }
 
-
             _draggingItem = null;
             _previewDrop = false;
             _rows = GetTreeItems().ToFlat();
@@ -911,5 +908,4 @@ 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]
-    public Func<TreeDropEventArgs<TItem>, Task>? OnItemDrop { get; set; }
+    [Parameter][Required]
+    public Func<TreeDropEventArgs<TItem>, Task> OnItemDrop { get; set; } = null!;
 
     private async Task DragStart(DragEventArgs e)
     {
@@ -336,7 +336,6 @@ private async Task DragStart(DragEventArgs e)
         {
             _expandAfterDrop = true;
             await ToggleNodeAsync();
-            StateHasChanged();
         }else
         {
             _expandAfterDrop = false;
@@ -389,10 +388,6 @@ private void DragLeaveChildBelow(DragEventArgs e)
 
     private async Task DropChildInside(DragEventArgs e)
     {
-        if (OnItemDrop is null)
-        {
-            return;
-        }
         _previewChildFirst = false;
         _previewChildLast = false;
         _previewBelow = false;
@@ -409,10 +404,6 @@ 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

@@ -1390,6 +1390,30 @@ public async Task Draggable_Basic_MoveAsSiblingBelow()
         Assert.Equal("Root1", nodes[2].Text); // Root1 成为最后一个根节点
     }
 
+    [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()
     {
@@ -1447,7 +1471,6 @@ 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");
@@ -1459,6 +1482,18 @@ 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
     }
 
     #endregion