support for .NET framework 3.5

Still have bugs

Net35/HandyControlDemo_Net35/UserControl/Styles/RichTextBoxDemoCtl.xaml.cs

@@ -0,0 +1,17 @@
+using HandyControlDemo.Tools.Converter;
+
+namespace HandyControlDemo.UserControl
+{
+    public partial class RichTextBoxDemoCtl
+    {
+        public RichTextBoxDemoCtl()
+        {
+            InitializeComponent();
+
+            var converter = new StringRepeatConverter();
+            converter.Convert(Properties.Langs.Lang.Title, null, 20.ToString(), null);
+            RunTitle.Text = converter.Convert(Properties.Langs.Lang.Title, null, 20, null)?.ToString();
+            RunText.Text = converter.Convert(Properties.Langs.Lang.Text, null, 1000, null)?.ToString();
+        }
+    }
+}