[WPF] Memory leak when you pop a TabbedPage (#3372) fixes #3267

* Fix [WPF] Memory leak when you pop a TabbedPage

* Update ViewRenderer.cs

* Update ViewRenderer.cs

Xamarin.Forms.Platform.WPF/Renderers/ViewRenderer.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Diagnostics;
 using System.Windows;
 using System.Windows.Controls;
 using WControl = System.Windows.Controls.Control;
@@ -23,6 +24,7 @@ public class ViewRenderer<TElement, TNativeElement> : IVisualElementRenderer, IE
 			new List<EventHandler<VisualElementChangedEventArgs>>();
 
 		VisualElementTracker _tracker;
+		bool _disposed;
 
 		IElementController ElementController => Element as IElementController;
 
@@ -161,19 +163,28 @@ protected void SetNativeControl(TNativeElement native)
 
 			Element.IsNativeStateConsistent = false;
 
-			Control.Loaded += (sender, e) =>
-			{
-				Element.IsNativeStateConsistent = true;
-				Appearing();
-			};
-			Control.Unloaded += (sender, e) => { Disappearing(); };
+			Control.Loaded += Control_Loaded;
+			Control.Unloaded += Control_Unloaded;
 
 			Control.GotFocus += OnGotFocus;
 			Control.LostFocus += OnLostFocus;
 
 			UpdateBackground();
 			UpdateAlignment();
 		}
+
+		private void Control_Loaded(object sender, RoutedEventArgs e)
+		{
+			Control.Loaded -= Control_Loaded;
+			Element.IsNativeStateConsistent = true;
+			Appearing();
+		}
+
+		private void Control_Unloaded(object sender, RoutedEventArgs e)
+		{
+			Control.Unloaded -= Control_Unloaded;
+			Disappearing();
+		}
 
 		protected virtual void Appearing()
 		{
@@ -260,8 +271,6 @@ void UpdateAlignment()
 			}
 		}
 
-		bool _disposed;
-
 		public void Dispose()
 		{
 			Dispose(true);
@@ -276,7 +285,6 @@ protected virtual void Dispose(bool disposing)
 
 			if (Control != null)
 			{
-				//Console.WriteLine("Dispose : " + this.Control.GetType());
 				Control.GotFocus -= OnGotFocus;
 				Control.LostFocus -= OnLostFocus;
 			}