Force a single instance of an application by remote desktop session

program.cs

static class Program
{
    [DllImport("user32.dll")]
    private static extern bool SetForegroundWindow(IntPtr hWnd);

    /// <summary>
    /// The main entry point for the application.
    /// </summary>
    [STAThread]
    static void Main(string[] args)
    {
        var currentProcess = Process.GetCurrentProcess();
        var runningProcess =
            Process.GetProcesses()
            .Where(
                p =>
                {
                    return 
                        p.Id != currentProcess.Id &&
                        p.ProcessName.Equals(currentProcess.ProcessName, StringComparison.Ordinal) &&
                        p.SessionId == currentProcess.SessionId;
                }
            )
            .FirstOrDefault();

        if (runningProcess != null)
        {
            SetForegroundWindow(runningProcess.MainWindowHandle);
            return;
        }

        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new TagPickerForm());
    }
}