add DiscreteGeometryKeyFrame

src/Shared/HandyControl_Shared/Media/Animation/DiscreteGeometryKeyFrame.cs

@@ -0,0 +1,22 @@
+using System.Windows;
+using System.Windows.Media;
+using System.Windows.Media.Animation;
+
+public class DiscreteGeometryKeyFrame : GeometryKeyFrame
+{
+    public DiscreteGeometryKeyFrame()
+    {
+    }
+
+    public DiscreteGeometryKeyFrame(Geometry value) : base(value)
+    {
+    }
+
+    public DiscreteGeometryKeyFrame(Geometry value, KeyTime keyTime) : base(value, keyTime)
+    {
+    }
+
+    protected override Freezable CreateInstanceCore() => new DiscreteGeometryKeyFrame();
+
+    protected override Geometry InterpolateValueCore(Geometry baseValue, double keyFrameProgress) => keyFrameProgress < 1.0 ? baseValue : Value;
+}

src/Shared/HandyControl_Shared/Media/Animation/GeometryKeyFrame.cs

@@ -5,6 +5,11 @@ using System.Windows.Media.Animation;
 
 public abstract class GeometryKeyFrame : Freezable, IKeyFrame
 {
+    protected GeometryKeyFrame()
+    {
+        
+    }
+
     protected GeometryKeyFrame(Geometry value)
     {
         Value = value;