Question

Possible Duplicate:
What is the correct way to create a single instance application?

How can I check if my application is already open? If my application is already running, I want to show it instead of opening a new instance.

Answer 1

[DllImport("user32.dll")]
private static extern Boolean ShowWindow(IntPtr hWnd, Int32 nCmdShow);

static void Main() 
{
    Process currentProcess = Process.GetCurrentProcess();
    var runningProcess = (from process in Process.GetProcesses()
                          where
                            process.Id != currentProcess.Id &&
                            process.ProcessName.Equals(
                              currentProcess.ProcessName,
                              StringComparison.Ordinal)
                          select process).FirstOrDefault();
    if (runningProcess != null)
    {
        ShowWindow(runningProcess.MainWindowHandle, SW_SHOWMAXIMIZED);
       return; 
    }
}

Method 2

static void Main()
{
    string procName = Process.GetCurrentProcess().ProcessName;

    // get the list of all processes by the "procName"       
    Process[] processes=Process.GetProcessesByName(procName);

    if (processes.Length > 1)
    {
        MessageBox.Show(procName + " already running");  
        return;
    } 
    else
    {
        // Application.Run(...);
    }
}