让通用对话框显示在窗口最前面

注：API函数GetForegroundWindow用来获得前台窗口的句柄，这里的“前台窗口”是指前台应用程序的活动窗口

类ForegroundWindow继承了框架提供的IWin32Window接口，并定义了一个静态的IWin32Window属性Instance，用来获得前台窗口的句柄。

public class ForegroundWindow : IWin32Window
 {
  private static ForegroundWindow _window = new ForegroundWindow();
  private ForegroundWindow(){}

  public static IWin32Window Instance
  {
   get { return _window; }
  }

  [DllImport("user32.dll")]
  private static extern IntPtr GetForegroundWindow();

  IntPtr IWin32Window.Handle
  {
   get
   {
    return GetForegroundWindow();
   }
  }
 public class Example1

{

   public void SaveFile(string str_filepath)

   {

       SaveFileDialog openfile=new SaveFileDialog();
      openfile.Title="请输入RTF文件名";
     openfile.Filter="word文档（*.rtf)|*.rtf";
     openfile.FilterIndex=0;
     openfile.ValidateNames=true;
     openfile.InitialDirectory= str_filepath;
     openfile.ShowDialog(ForegroundWindow.Instance);

  }

}