hide show process in c#

Im trying to make a show/hide window but no way to make work a show window when i hide it. I already read in many forums but no way to do it work, sone one can help???

private const int SW_HIDE = 0;

private const int SW_SHOW = 5;         

[DllImport("User32")]         

private static extern int ShowWindow(int hwnd, int nCmdShow);  

//WORKING         

private void button1_Click(object sender, EventArgs e)        

{             

   int hWnd;             

   Process[] processRunning = Process.GetProcesses();             

   foreach (Process pr in processRunning)             

   {                 

      if (pr.ProcessName == "notepad")                 

      {                     

         hWnd = pr.MainWindowHandle.ToInt32();                     

         ShowWindow(hWnd, SW_HIDE); 

       }             

   }

} 

//NOT WORKING         

private void button2_Click(object sender, EventArgs e)         

{            

   int hWnd;            

   Process[] processRunning = Process.GetProcesses();             

   foreach (Process pr in processRunning)             

   {

      if (pr.ProcessName == "notepad")                 

      {

         hWnd = pr.MainWindowHandle.ToInt32();                

         ShowWindow(hWnd, SW_SHOW);

      }

   } 

}