Cache selected views in SimpleViewLocator

Add a `ConditionalWeakTable`-based view cache keyed by view model instance for `MsgViewModel`, `ClashProxiesViewModel`, and `ClashConnectionsViewModel` so repeated bindings reuse the same control. The locator now also handles missing registrations and null factory results more explicitly by returning descriptive `TextBlock` messages.

v2rayN/v2rayN.Desktop/Common/SimpleViewLocator.cs

@@ -1,3 +1,4 @@
+using System.Runtime.CompilerServices;
 using Avalonia.Controls.Templates;
 using v2rayN.Desktop.ViewModels;
 using v2rayN.Desktop.Views;
@@ -9,6 +10,7 @@ public class SimpleViewLocator : IDataTemplate
     private static readonly Lazy<SimpleViewLocator> _instance = new(() => new SimpleViewLocator());
 
     private readonly Dictionary<Type, Func<Control?>> _locator = new();
+    private readonly ConditionalWeakTable<object, Control> _cachedViews = new();
 
     private SimpleViewLocator()
     {
@@ -45,9 +47,18 @@ public class SimpleViewLocator : IDataTemplate
             return new TextBlock { Text = "No VM provided" };
         }
 
-        _locator.TryGetValue(data.GetType(), out var factory);
+        var vmType = data.GetType();
+        if (!_locator.TryGetValue(vmType, out var factory))
+        {
+            return new TextBlock { Text = $"VM Not Registered: {vmType}" };
+        }
 
-        return factory?.Invoke() ?? new TextBlock { Text = $"VM Not Registered: {data.GetType()}" };
+        if (ShouldCache(vmType))
+        {
+            return _cachedViews.GetValue(data, _ => CreateView(factory, vmType));
+        }
+
+        return CreateView(factory, vmType);
     }
 
     public bool Match(object? data)
@@ -55,6 +66,18 @@ public class SimpleViewLocator : IDataTemplate
         return data is MyReactiveObject;
     }
 
+    private static bool ShouldCache(Type vmType)
+    {
+        return vmType == typeof(MsgViewModel)
+               || vmType == typeof(ClashProxiesViewModel)
+               || vmType == typeof(ClashConnectionsViewModel);
+    }
+
+    private static Control CreateView(Func<Control?> factory, Type vmType)
+    {
+        return factory.Invoke() ?? new TextBlock { Text = $"View Factory Returned Null: {vmType}" };
+    }
+
     public void RegisterViewFactory<TViewModel>(Func<Control> factory) where TViewModel : class
     {
         _locator.Add(typeof(TViewModel), factory);