support for .NET framework 3.5

Still have bugs

Net35/HandyControlDemo_Net35/ViewModel/WindowDemoViewModel.cs

@@ -0,0 +1,23 @@
+using System.Windows;
+using GalaSoft.MvvmLight.Command;
+using HandyControlDemo.Tools;
+
+namespace HandyControlDemo.ViewModel
+{
+    public class WindowDemoViewModel
+    {
+        private RelayCommand<string> _openWindowCmd;
+
+        public RelayCommand<string> OpenWindowCmd =>
+            _openWindowCmd ?? (_openWindowCmd = new RelayCommand<string>(OpenWindow));
+
+        private void OpenWindow(string windowTag)
+        {
+            if (AssemblyHelper.CreateInternalInstance($"Window.{windowTag}") is System.Windows.Window window)
+            {
+                window.Owner = Application.Current.MainWindow;
+                window.ShowDialog();
+            }
+        }
+    }
+}