Add Default Consturctor to TransitionEffectExtension

Author: l1pton17

MainDemo.Wpf/TransitionsDemo/Slide5_TransitioningContent.xaml

@@ -36,7 +36,7 @@
                     <Setter Property="Mode" Value="PrimaryLight" />
                 </Style>
             </ItemsControl.Resources>
-            <materialDesign:TransitioningContent OpeningEffect="{materialDesign:TransitionEffect ExpandIn}">
+            <materialDesign:TransitioningContent OpeningEffect="{materialDesign:TransitionEffect Kind=ExpandIn}">
                 <materialDesign:ColorZone>
                     <materialDesign:PackIcon Kind="Phone" VerticalAlignment="Center" HorizontalAlignment="Center" />
                 </materialDesign:ColorZone>

MaterialDesignThemes.Wpf/Transitions/TransitionEffectExtension.cs

@@ -6,6 +6,11 @@ namespace MaterialDesignThemes.Wpf.Transitions
     [MarkupExtensionReturnType(typeof(TransitionEffectBase))]
     public class TransitionEffectExtension : MarkupExtension
     {
+        public TransitionEffectExtension()
+        {
+            Kind = TransitionEffectKind.None;
+        }
+
         public TransitionEffectExtension(TransitionEffectKind kind)
         {
             Kind = kind;