添加项目文件。

gong-wpf-dragdrop/src/Showcase/ViewModels/SimpleCommand.cs

@@ -0,0 +1,35 @@
+using System;
+using System.Windows.Input;
+
+namespace Showcase.WPF.DragDrop.ViewModels
+{
+    public class SimpleCommand : ICommand
+    {
+        public SimpleCommand(Action<object> execute = null, Predicate<object> canExecute = null)
+        {
+            this.CanExecuteDelegate = canExecute;
+            this.ExecuteDelegate = execute;
+        }
+
+        public Predicate<object> CanExecuteDelegate { get; set; }
+
+        public Action<object> ExecuteDelegate { get; set; }
+
+        public bool CanExecute(object parameter)
+        {
+            var canExecute = this.CanExecuteDelegate;
+            return canExecute == null || canExecute(parameter);
+        }
+
+        public event EventHandler CanExecuteChanged
+        {
+            add { CommandManager.RequerySuggested += value; }
+            remove { CommandManager.RequerySuggested -= value; }
+        }
+
+        public void Execute(object parameter)
+        {
+            this.ExecuteDelegate?.Invoke(parameter);
+        }
+    }
+}