How to wait until remote .NET debugger attached

Today I ran into a problem were I needed to remote-debug a program. The program was launched from another system, so I really don't have an opportunity to interact with it on the command line. I could change its source easily though.

What I needed to happen was for the program to start normally, and then wait for me to attach to it with a debugger. I couldn't come up with a way to do it that made me happy. I did find the bug, but without the help of the debugger.

while(true) { }

Kept the process alive, and then I could "set next statement" with the debugger, but it seemed awkward and rude.

Console.ReadLine();

Seemed odd to type since there wasn't actually a Console for me to press enter at. (It didn't work, either. Set next statement and then run takes you back into the ReadLine() wait.)

So what kind of code can I insert into a .NET/CLR/C# program that says "wait here until I can attach with a debugger"?

You can use the System.Diagnostics.Debugger.IsAttached property to check if a debugger is attached to the process. This application will wait until a debugger has been attached:

using System;
using System.Diagnostics;
using System.Threading;

namespace DebugApp
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Waiting for debugger to attach");
            while (!Debugger.IsAttached)
            {
                Thread.Sleep(100);
            }
            Console.WriteLine("Debugger attached");
        }
    }
}

This sounds like exactly what you need:

Debugger.Launch();

http://msdn.microsoft.com/en-us/library/system.diagnostics.debugger.launch.aspx

"Launches and attaches a debugger to the process."

Steven Behnke

I don't know, since I've never tried it but I wonder if you could use System.Diagnostics.Debugger.Break() in order to have it hit a breakpoint and then wait for a debugger to attach. I assume a remote debugger would work, but I do not know for sure and currently do not have access to my home environment where I could easily mock it up and test my theory. There's an MSDN article talking about using it in an ASP.Net application so I imagine it would work.

Attaching remote debugger works exactly the same as using local debugger.

First, do the usual:

System.Diagnostics.Debugger.Launch();

You will see a prompt to chose debugger. At this point the execution is suspended, so so you can attach remote debugger and select "No" from the prompt.