修复bug和新增部分功能

Sai.Toolkit.Core/Heplers/SingletonViewHelper.cs

@@ -6,7 +6,7 @@ namespace Sai.Toolkit.Core.Helpers;
 public sealed record SingletonViewHelper<T>
     where T : Window, new()
 {
-    private static T instance;
+    private static T _instance;
     private static readonly object Padlock = new();
 
     private SingletonViewHelper() { }
@@ -15,21 +15,21 @@ public sealed record SingletonViewHelper<T>
     {
         isNewCreate = false;
         //double-check locking
-        if (instance == null)
+        if (_instance == null)
         {
             isNewCreate = true;
             lock (Padlock)
             {
-                instance ??= new T();
-                instance.Closed += OnWindowClosed;
+                _instance ??= new T();
+                _instance.Closed += OnWindowClosed;
             }
         }
-        return instance;
+        return _instance;
     }
 
     private static void OnWindowClosed(object sender, EventArgs e)
     {
-        instance = null;
+        _instance = null;
     }
 }