add NumericUpDownPlus style

now you can clear, verify the value of NumericUpDown

HandyControlDemo/UserControl/Controls/NumericUpDownDemoCtl.xaml.cs

@@ -1,4 +1,6 @@
-// ReSharper disable once CheckNamespace
+using HandyControl.Data;
+
+// ReSharper disable once CheckNamespace
 namespace HandyControlDemo.UserControl
 {
     public partial class NumericUpDownDemoCtl
@@ -6,6 +8,12 @@ namespace HandyControlDemo.UserControl
         public NumericUpDownDemoCtl()
         {
             InitializeComponent();
+
+            NumericUpDownCustomVerify.VerifyFunc = str => double.TryParse(str, out var v)
+                ? v % 2 < 1e-06 
+                    ? OperationResult.Failed(Properties.Langs.Lang.Error) 
+                    : OperationResult.Success()
+                : OperationResult.Failed(Properties.Langs.Lang.Error);
         }
     }
 }