优化更新代码，添加界面功能并整合

WPFluent/Controls/VirtualizingPanel/ItemRange.cs

@@ -0,0 +1,28 @@
+
+
+
+/* Based on VirtualizingWrapPanel created by S. Bäumlisberger licensed under MIT license.
+   https://github.com/sbaeumlisberger/VirtualizingWrapPanel
+
+   Copyright (C) S. Bäumlisberger
+   All Rights Reserved. */
+
+namespace WPFluent.Controls;
+
+/// <summary>
+/// Items range. <para>Based on <see href="https://github.com/sbaeumlisberger/VirtualizingWrapPanel"/>.</para>
+/// </summary>
+public readonly struct ItemRange
+{
+    public ItemRange(int startIndex, int endIndex) : this()
+    {
+        StartIndex = startIndex;
+        EndIndex = endIndex;
+    }
+
+    public readonly bool Contains(int itemIndex) => itemIndex >= StartIndex && itemIndex <= EndIndex;
+
+    public int EndIndex { get; }
+
+    public int StartIndex { get; }
+}