support for .NET framework 3.5

Still have bugs

Net35/HandyControlDemo_Net35/UserControl/Controls/NumericUpDownDemoCtl.xaml.cs

@@ -0,0 +1,19 @@
+using HandyControl.Data;
+
+
+namespace HandyControlDemo.UserControl
+{
+    public partial class NumericUpDownDemoCtl
+    {
+        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);
+        }
+    }
+}