添加项目文件。

Wpf.Ui.Extend/Controls/MultiTreeView/MultiTreeViewItem.cs

@@ -0,0 +1,81 @@
+using System;
+using System.Linq;
+using System.Windows;
+using System.Windows.Controls;
+
+using Wpf.Ui.Extend.Extensions;
+
+namespace Wpf.Ui.Extend.Controls;
+public class MultiTreeViewItem : TreeViewItem
+{
+    private MultiTreeView ParentMultiTreeView
+    {
+        //get { return ItemsControl.ItemsControlFromItemContainer(this) as MultiTreeView; }
+        get { return this.FindParent<MultiTreeView>(); }
+    }
+    static MultiTreeViewItem()
+    {
+        DefaultStyleKeyProperty.OverrideMetadata(typeof(MultiTreeViewItem), new FrameworkPropertyMetadata(typeof(MultiTreeViewItem)));
+        IsExpandedProperty.OverrideMetadata(typeof(MultiTreeViewItem), new FrameworkPropertyMetadata(true));
+    }
+
+    public bool? IsChecked
+    {
+        get { return (bool?)GetValue(IsCheckedProperty); }
+        set { SetValue(IsCheckedProperty, value); }
+    }
+
+    public static readonly DependencyProperty IsCheckedProperty =
+        DependencyProperty.Register(nameof(IsChecked), typeof(bool?), typeof(MultiTreeViewItem), new PropertyMetadata(false, new PropertyChangedCallback(OnIsCheckedChanged)));
+
+    /// <summary>
+    /// 获取项的容器。
+    /// </summary>
+    protected override DependencyObject GetContainerForItemOverride()
+    {
+        return new MultiTreeViewItem();
+    }
+
+    /// <summary>
+    /// 确定项是否是其自己的容器。
+    /// </summary>
+    protected override bool IsItemItsOwnContainerOverride(object item)
+    {
+        return item is MultiTreeViewItem;
+    }
+
+    private static void OnIsCheckedChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
+    {
+        var currentChildren = d.FindVisualChildren<MultiTreeViewItem>();
+        if (e.NewValue == e.OldValue)
+        {
+            return;
+        }
+        if (d is MultiTreeViewItem currentItem)
+        {
+            currentItem?.ParentMultiTreeView?.NotifyMultiTreeViewItemClicked(currentItem);
+            foreach (var item in currentItem.FindVisualChildren<MultiTreeViewItem>())
+            {
+                if (e.NewValue != null)
+                {
+                    item.IsChecked = (bool)e.NewValue;
+                }
+            }
+        }
+
+        var parent = d.FindParent<MultiTreeViewItem>();
+        if (parent != null)
+        {
+            var children = parent.FindVisualChildren<MultiTreeViewItem>();
+            if (children.All(d => d.IsChecked == true))
+            {
+                parent.IsChecked = true;
+            }
+            else
+            {
+                parent.IsChecked = children.All(d => d.IsChecked == false) ? false : null;
+            }
+        }
+       
+    }
+}