Add a InteractiveDialog demo for the DialogExtension.

HandyControlDemo/ViewModel/Basic/InteractiveDialogViewModel.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Windows.Input;
+using GalaSoft.MvvmLight;
+using GalaSoft.MvvmLight.CommandWpf;
+using HandyControl.Tools.Extension;
+
+namespace HandyControlDemo.ViewModel.Basic
+{
+    public class InteractiveDialogViewModel : ViewModelBase, IDialogResultable
+    {
+        private string _message;
+
+
+        public object Result { get; set; }
+
+        public Action ClosureToken { get; set; }
+
+        public ICommand CloseCommand { get; }
+
+        public string Message
+        {
+            get => _message;
+            set => Set(ref _message, value);
+        }
+
+
+        public InteractiveDialogViewModel()
+        {
+            CloseCommand = new RelayCommand<string>(result =>
+            {
+                Result = result;
+                ClosureToken();
+            });
+        }
+    }
+}