Single application instance

I needed my app to be a single-instance app. It was easy to implement, like so:

bool mutexIsNew;
Mutex mutex = new Mutex(true, "SomeUniqueID", out mutexIsNew);
if (mutexIsNew)
  Application.Run(new MainForm());

A problem arose though when my app started to need to receive command line arguments. How do you also pass those onto the original app? There is a class for this purpose named
“WindowsFormsApplicationBase”, it’s in Microsoft.VisualBasic.dll

01: Add a class to your project like so:

internal class SingleInstanceApplication : WindowsFormsApplicationBase
{
  private MainForm MainFormInstance;
  internal SingleInstanceApplication()
  {
    IsSingleInstance = true;
    EnableVisualStyles = true;
    MainFormInstance = new MainForm();
    MainForm = MainFormInstance;
  }

  protected override bool OnStartup(StartupEventArgs eventArgs)
  {
    return base.OnStartup(eventArgs);
    MainFormInstance.AcceptCommandArguments(eventArgs.CommandLine);
  }

  protected override void OnStartupNextInstance(StartupNextInstanceEventArgs eventArgs)
  {
    base.OnStartupNextInstance(eventArgs);
    MainFormInstance.AcceptCommandArguments(eventArgs.CommandLine);
  }
}

02: Add a method to your MainForm class like so:

internal void AcceptCommandArguments(IList args)
{
}

03: Finally change your project source code like so:

[STAThread]
static void Main(string[] args)
{
  Application.EnableVisualStyles();
  Application.SetCompatibleTextRenderingDefault(false);
  SingleInstanceApplication singleInstanceApplication = new SingleInstanceApplication();
  singleInstanceApplication.Run(args);
}