[UWP] Unhook Entry and Editor event handlers during Dispose (#114)

* [UWP] Null-check Element in native event handlers for Entry

* Unhook event handlers in Dispose

* Prevent race condition using Control in event handlers

2 files changed, 29 insertions, 6 deletions

diff --git a/Xamarin.Forms.Platform.WinRT/EditorRenderer.cs b/Xamarin.Forms.Platform.WinRT/EditorRenderer.cs
index d6236871..7c4acfba 100644
--- a/Xamarin.Forms.Platform.WinRT/EditorRenderer.cs
+++ b/Xamarin.Forms.Platform.WinRT/EditorRenderer.cs
@@ -22,10 +22,10 @@ namespace Xamarin.Forms.Platform.WinRT
 				{
 					var textBox = new TextBox { AcceptsReturn = true, TextWrapping = TextWrapping.Wrap };
 
+					SetNativeControl(textBox);
+
 					textBox.TextChanged += OnNativeTextChanged;
 					textBox.LostFocus += OnLostFocus;
-
-					SetNativeControl(textBox);
 				}
 
 				UpdateText();
@@ -37,6 +37,17 @@ namespace Xamarin.Forms.Platform.WinRT
 			base.OnElementChanged(e);
 		}
 
+		protected override void Dispose(bool disposing)
+		{
+			if (disposing && Control != null)
+			{
+				Control.TextChanged -= OnNativeTextChanged;
+				Control.LostFocus -= OnLostFocus;
+			}
+
+			base.Dispose(disposing);
+		}
+
 		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
 		{
 			if (e.PropertyName == Editor.TextColorProperty.PropertyName)
@@ -65,12 +76,12 @@ namespace Xamarin.Forms.Platform.WinRT
 
 		void OnLostFocus(object sender, RoutedEventArgs e)
 		{
-			Element?.SendCompleted();
+			Element.SendCompleted();
 		}
 
 		void OnNativeTextChanged(object sender, Windows.UI.Xaml.Controls.TextChangedEventArgs args)
 		{
-			Element?.SetValueCore(Editor.TextProperty, Control.Text);
+			Element.SetValueCore(Editor.TextProperty, Control.Text);
 		}
 
 		void UpdateFont()
diff --git a/Xamarin.Forms.Platform.WinRT/EntryRenderer.cs b/Xamarin.Forms.Platform.WinRT/EntryRenderer.cs
index f02abe3c..1a9fa767 100644
--- a/Xamarin.Forms.Platform.WinRT/EntryRenderer.cs
+++ b/Xamarin.Forms.Platform.WinRT/EntryRenderer.cs
@@ -27,10 +27,11 @@ namespace Xamarin.Forms.Platform.WinRT
 				if (Control == null)
 				{
 					var textBox = new FormsTextBox { Style = Windows.UI.Xaml.Application.Current.Resources["FormsTextBoxStyle"] as Windows.UI.Xaml.Style };
+					
+					SetNativeControl(textBox);
 
 					textBox.TextChanged += OnNativeTextChanged;
 					textBox.KeyUp += TextBoxOnKeyUp;
-					SetNativeControl(textBox);
 				}
 
 				UpdateIsPassword();
@@ -44,6 +45,17 @@ namespace Xamarin.Forms.Platform.WinRT
 			}
 		}
 
+		protected override void Dispose(bool disposing)
+		{
+			if (disposing && Control != null)
+			{
+				Control.TextChanged -= OnNativeTextChanged;
+				Control.KeyUp -= TextBoxOnKeyUp;
+			}
+
+			base.Dispose(disposing);
+		}
+
 		protected override void OnElementPropertyChanged(object sender, PropertyChangedEventArgs e)
 		{
 			base.OnElementPropertyChanged(sender, e);
@@ -107,7 +119,7 @@ namespace Xamarin.Forms.Platform.WinRT
 
 		void TextBoxOnKeyUp(object sender, KeyRoutedEventArgs args)
 		{
-			if (args.Key != VirtualKey.Enter)
+			if (args?.Key != VirtualKey.Enter)
 				return;
 
 			Element.SendCompleted();