WPF MVVM 中怎样在ViewModel总打开的对话框在窗体之前

 1     /// <summary>
 2     /// 句柄转换IWin32Window类
 3     /// </summary>
 4     public class WindowWrapper : System.Windows.Forms.IWin32Window
 5     {
 6         /// <summary>
 7         /// 构造函数
 8         /// </summary>
 9         /// <param name="handle">句柄</param>
10         public WindowWrapper(IntPtr handle)
11         {
12             _hwnd = handle;
13         }
14 
15         public IntPtr Handle
16         {
17             get { return _hwnd; }
18         }
19 
20         private IntPtr _hwnd;
21     }

   private void ExecuteShowDialogCommand()
        {
            Process[] procs = Process.GetProcessesByName("程序进程");
            if (procs.Length != 0)
            {
                IntPtr hwnd = procs[0].MainWindowHandle;
                var printPreviewDocument = new PrintPreviewDialog();
                printPreviewDocument.ShowDialog(new WindowWrapper(hwnd));
            }
            else
            {
                MessageBox.Show("无此进程");
            }
        }