doc: 更新拖动到子节点时父节点自动展开功能

Author: ArgoZhang

src/BootstrapBlazor.Server/Components/Samples/TreeViews.razor.cs

@@ -121,7 +121,21 @@ private Task OnDragItemEndAsync(TreeViewDragContext<TreeFoo> context)
                 source.ParentId = context.IsChildren ? target.Id : target.ParentId;
             }
         }
-        DraggableItems = TreeFoo.CascadingTree(items);
+
+        var expandNodeIds = new List<string>();
+        Action<TreeViewItem<TreeFoo>>? cb = null;
+        if (context.IsChildren)
+        {
+            // 自动展开目标节点
+            cb = item =>
+            {
+                if (item.Value.Id == context.Target.Value.Id)
+                {
+                    item.IsExpand = true;
+                }
+            };
+        }
+        DraggableItems = TreeFoo.CascadingTree(items, cb);
         DraggableItems[0].IsExpand = true;
         if (DraggableItems.Count > 1)
         {

src/BootstrapBlazor.Server/Data/TreeFoo.cs

@@ -177,10 +177,11 @@ public static List<TreeViewItem<TreeFoo>> GetCheckedTreeItems(string? parentId =
     /// 树状数据层次化方法
     /// </summary>
     /// <param name="items">数据集合</param>
-    public static List<TreeViewItem<TreeFoo>> CascadingTree(IEnumerable<TreeFoo> items) => items.CascadingTree(null, (foo, parent) => foo.ParentId == parent?.Value.Id, foo => new TreeViewItem<TreeFoo>(foo)
+    /// <param name="treeviewItemCallback">节点状态回调方法</param>
+    public static List<TreeViewItem<TreeFoo>> CascadingTree(IEnumerable<TreeFoo> items, Action<TreeViewItem<TreeFoo>>? treeviewItemCallback = null) => items.CascadingTree(null, (foo, parent) => foo.ParentId == parent?.Value.Id, foo => new TreeViewItem<TreeFoo>(foo)
     {
         Text = foo.Text,
         Icon = foo.Icon,
         IsActive = foo.IsActive
-    });
+    }, treeviewItemCallback);
 }