WPF Command Line

First, find this attribute at the top of your App.xaml file and remove it:

StartupUri="Window1.xaml"

That means that the application won't automatically instantiate your main window and show it.

Next, override the OnStartup method in your App class to perform the logic:

protected override void OnStartup(StartupEventArgs e){    base.OnStartup(e);    if ( /* test command-line params */ )    {        /* do stuff without a GUI */    }    else    {        new Window1().ShowDialog();    }    this.Shutdown();}

To check for the existence of your argument - in Matt's solution use this for your test:

e.Args.Contains("MyTriggerArg")

A combination of the above solutions, for .NET 4.0+ with output to the console:

[DllImport("Kernel32.dll")]public static extern bool AttachConsole(int processID);protected override void OnStartup(StartupEventArgs e){    base.OnStartup(e);    if (e.Args.Contains("--GUI"))    {        // Launch GUI and pass arguments in case you want to use them.        new MainWindow(e).ShowDialog();    }    else    {        //Do command line stuff        if (e.Args.Length > 0)        {            string parameter = e.Args[0].ToString();            WriteToConsole(parameter);        }    }    Shutdown();}public void WriteToConsole(string message){    AttachConsole(-1);    Console.WriteLine(message);}

Alter the constructor in your MainWindow to accept arguments:

public partial class MainWindow : Window{    public MainWindow(StartupEventArgs e)    {        InitializeComponent();    }}

And don't forget to remove:

StartupUri="MainWindow.xaml"