11 May, 2010

Visual Studio 2010 Debugger Not Attaching Problem

Since we moved to Visual Studio 2010, I've had 3 people ask me: "Is there some sort of magic you have to do to get VS2010 to attach to the IIS worker process (w3wp)"?

So, in the interest of (hopefully) saving you some time, I figure I'd write a little bit about what the problem with the VS2010 debugger is. Actually, the debugger is fine, it doesn't have any problems attaching; it's actually VS2010 itself that has a minor bug(?) while attaching.

As you can see in the image below, under normal circumstances Visual Studio automatically detects what type of code the process is running and automatically chooses the correct debugger:

Unfortunately, however, I've found that sometimes VS2010 cannot detect the correct code type in the worker process and attaches to the process using the .NET 4.0 debugger (I don't know why this happens nor do I know if this happens when attaching to other processes).

If you attach using the wrong debugger, you'll attach, but you'll notice that none of your symbols ever load and therefore none of your breakpoints ever hit. It's actually somewhat frustrating because everything looks like it should be working but doesn't.

But enough talk about the problem; here's all you need to do to solve the problem if you notice you're not using the right debugger:
  1. Hit the "Select" button the in "Attach to Process" window.
  2. Select the "Debug these code types:" radio button
  3. Check all the code types you want to debug.
You're shooting for something like this:

I've found that after you choose the code types you want to debug, VS2010 remembers your selection, so you should never have problems attaching in the future.

Now, if I could just get rid of that stupid dialog asking me to confirm if I really want to attach to the "potentially dangerous" w3wp process, I'd be set. :)