初步完成邮件功能

DMS.WPF/Interfaces/IDialogViewModel.cs

@@ -0,0 +1,13 @@
+namespace DMS.WPF.Interfaces
+{
+    /// <summary>
+    /// 对话框视图模型接口
+    /// </summary>
+    public interface IDialogViewModel
+    {
+        /// <summary>
+        /// 关闭请求事件
+        /// </summary>
+        event Action<bool?> CloseRequested;
+    }
+}