C#

public static class SingletonApp
{
	[DllImport( "user32.dll" )]
	static extern bool SetForegroundWindow( IntPtr hWnd );
	
	[DllImport( "user32.dll" )]
	static extern bool ShowWindowAsync( IntPtr hWnd , int nCmdShow );

	[DllImport( "user32.dll" )]
	static extern bool IsIconic( IntPtr hWnd ); 

        const int SW_RESTORE = 9;

	static Mutex m_Mutex;

	public static void Run( Form mainForm )
	{
	     bool first = IsFirstInstance( );
	     if( first )
	     {
		  Application.ApplicationExit += OnExit;
		  Application.Run( mainForm );
	     }
	     else
	     {
		  Process current = Process.GetCurrentProcess( );
		  Process[ ] procs = Process.GetProcessesByName( current.ProcessName );
		  IntPtr mainWindowHandle = procs[0].MainWindowHandle;
		  if( IsIconic( mainWindowHandle ) )
		  {
			ShowWindowAsync( mainWindowHandle , SW_RESTORE );
                  }
			SetForegroundWindow( mainWindowHandle ); 
	     }
        }

	static bool IsFirstInstance( )
	{
	      Assembly assembly = Assembly.GetEntryAssembly( );
	      string name = assembly.FullName;

	      m_Mutex = new Mutex( false , name );
	      bool owned = false;
	      owned = m_Mutex.WaitOne( TimeSpan.FromSeconds(0) , false );
	      return owned;
	}

	static void OnExit( object sender , EventArgs args )
	{
	      m_Mutex.ReleaseMutex( );
	      m_Mutex.Close( );
	}
}

nelsonpaixao wrote:

but i want this way and i really dont know where the codes goes wrong

Application.Run(new form1())