Does Your App Know Where it's Running

Have you ever wondered how to determine if your application is running as a standalone app or from within the Visual Studio IDE? I needed to do that today, and it took some scrounging around, but this is what I came up with.

If you go look in your (compiled) project's bin\debug (or bin\release) folder, you'll probably find a file named something like this:

MyApplication.vshost.exe

That application is an execution proxy used by Visual Studio to run your actual application. It provides three primary benefits to your development efforts:

It provides the following benefits:

* It improves performance by creating the AppDomain and initializing the debugger.

* It simulates a partial trust environment inside the IDE

* It allows design-time expression evaluation and supports the Immediate window.

Now that we know what it does (not that it really matters), let's exploit it. Essentially, you need to do two things to make this tip work:

0) Calling Application.ExecutablePath returns the full path to your actual application, i.e. C:\dev\MySolution\MyProj\bin\debug\MyApp.exe

1) If you use InteropServices to call GetModuleFileName, the returned path is C:\dev\MySolution\MyProj\bin\debug\MyApp.vshost.exe.

If the two names do NOT match, you're app is running in the IDE (even if the debugger isn't attached).

Ain't life a peach sometimes? Here's the whole code snippet.

using System.Windows.Forms;
using System.InteropServices;

public static class Globals
{
    [DllImport("kernel32.dll", SetLastError=true)]
    private static extern int GetModuleFileName([In]IntPtr hModule, 
                                                [Out]StringBuilder lpFilename, 
                                                [In][MarshalAs(UnmanagedType.U4)] int nSize);

    //--------------------------------------------------------------------------------
    public static bool RunningInVisualStudio()
    {
        StringBuilder moduleName = new StringBuilder(1024);
        int result = GetModuleFileName(IntPtr.Zero, moduleName, moduleName.Capacity);
        string appName = Application.ExecutablePath.ToLower();
        return (appName != moduleName.ToString().ToLower());
    }
}

One caveat exists - This technique can be rendered useless by going to the project's Properties page, clicking on the Debug tab, and then unchecking the check box that reads "Enable the Visual Studio Hosting Process". My advice - don't uncheck that box.