Mark selection click events as handled.

src/Perspex.Controls/ListBox.cs

@@ -38,7 +38,7 @@ namespace Perspex.Controls
 
             if (e.NavigationMethod == NavigationMethod.Directional)
             {
-                UpdateSelectionFromEventSource(
+                e.Handled = UpdateSelectionFromEventSource(
                     e.Source,
                     true,
                     (e.InputModifiers & InputModifiers.Shift) != 0);
@@ -52,7 +52,7 @@ namespace Perspex.Controls
 
             if (e.MouseButton == MouseButton.Left || e.MouseButton == MouseButton.Right)
             {
-                UpdateSelectionFromEventSource(
+                e.Handled = UpdateSelectionFromEventSource(
                     e.Source,
                     true,
                     (e.InputModifiers & InputModifiers.Shift) != 0,

src/Perspex.Controls/Primitives/TabStrip.cs

@@ -56,7 +56,7 @@ namespace Perspex.Controls.Primitives
 
             if (e.NavigationMethod == NavigationMethod.Directional)
             {
-                UpdateSelectionFromEventSource(e.Source);
+                e.Handled = UpdateSelectionFromEventSource(e.Source);
             }
         }
 
@@ -67,7 +67,7 @@ namespace Perspex.Controls.Primitives
 
             if (e.MouseButton == MouseButton.Left)
             {
-                UpdateSelectionFromEventSource(e.Source);
+                e.Handled = UpdateSelectionFromEventSource(e.Source);
             }
         }
     }