How do I create a C# app that decides itself whether to show as a console or windowed app?

Question

Is there a way to launch a C# application with the following features?

1. It determines by command-line parameters whether it is a windowed or console app
2. It doesn't show a console when it is asked to be windowed and doesn't show a GUI window when it is running from the console.

For example,

myapp.exe /help

would output to stdout on the console you used, but

myapp.exe

by itself would launch my Winforms or WPF user interface.

The best answers I know of so far involve having two separate exe and use IPC, but that feels really hacky.

What options do I have and trade-offs can I make to get the behavior described in the example above? I'm open to ideas that are Winform-specific or WPF-specific, too.

Answer 1

Make the app a regular windows app, and create a console on the fly if needed.

More details at this link (code below from there)

using System; using System.Windows.Forms;  namespace WindowsApplication1 {   static class Program {     [STAThread]     static void Main(string[] args) {       if (args.Length > 0) {         // Command line given, display console         if ( !AttachConsole(-1) ) { // Attach to an parent process console            AllocConsole(); // Alloc a new console         }          ConsoleMain(args);       }       else {         Application.EnableVisualStyles();         Application.SetCompatibleTextRenderingDefault(false);         Application.Run(new Form1());       }     }     private static void ConsoleMain(string[] args) {       Console.WriteLine("Command line = {0}", Environment.CommandLine);       for (int ix = 0; ix < args.Length; ++ix)         Console.WriteLine("Argument{0} = {1}", ix + 1, args[ix]);       Console.ReadLine();     }      [System.Runtime.InteropServices.DllImport("kernel32.dll")]     private static extern bool AllocConsole();      [System.Runtime.InteropServices.DllImport("kernel32.dll")]     private static extern bool AttachConsole(int pid);    } } 

Answer 2

I basically do that the way depicted in Eric's answer, additionally I detach the console with FreeConsole and use the SendKeys command to get the command prompt back.

    [DllImport("kernel32.dll")]     private static extern bool AllocConsole();      [DllImport("kernel32.dll")]     private static extern bool AttachConsole(int pid);      [DllImport("kernel32.dll", SetLastError = true)]     private static extern bool FreeConsole();      [STAThread]     static void Main(string[] args)     {         if (args.Length > 0 && (args[0].Equals("/?") || args[0].Equals("/help", StringComparison.OrdinalIgnoreCase)))         {             // get console output             if (!AttachConsole(-1))                 AllocConsole();              ShowHelp(); // show help output with Console.WriteLine             FreeConsole(); // detach console              // get command prompt back             System.Windows.Forms.SendKeys.SendWait("{ENTER}");               return;         }          // normal winforms code         Application.EnableVisualStyles();         Application.SetCompatibleTextRenderingDefault(false);         Application.Run(new MainForm());      }