Visual Studio breakpoints not being hit

Question

I'm working with an ASP.NET MVC project that seems to be having some issues when attaching to the IIS process (w3wp.exe). I'm running the solution and IIS 8.5 on my own local machine so I wouldn't think that this has anything to do with our network. What's strange to me is that I'm able to hit the breakpoints on any other solution I debug locally.

The issue I'm having exactly is that the breakpoints turn to red, hollow circles and never get hit. Usually the fix for this is a Clean/Rebuild of the solution but this hasn't worked. I've confirmed the code is being updated by adding "throw new Exception" to a page and ensuring it shows the exception. Again, this problem is only happening with this one solution. Any other solution I run the debugger with works fine. I've also tried restarting the app pool, the website, IIS, and also my computer.

A few of the articles I read mentioned that anti-virus programs can block a remote debugger from accessing the process. However, the entire setup is contained on my local machine so it doesn't sound like that would be the issue. It does concern me a bit though because we recently hired a new IT guy that's been making a lot of changes to everyone's machine.

One other point to add that's unique about this web application is the binding in IIS. The binding is "*" in order to leverage some custom functionality related to subdomains.

In the meantime, I'll continue to look for a solution but if anybody has any ideas what may be causing this one solution to not debug properly I'd really appreciate it.

EDIT: Found a solution that suggested deleting the ASP.NET temporary files. No luck.

Answer 1

Solved. Ended up being an incorrect configuration selected in the debug menu. I had mistakenly switched it to a release configuration that could not load the symbols for the document. Switched it to a debug configuration and the breakpoints hit just fine now.

To add on to what Abacus mentioned below, it could also be a web.config transform that is messing with your build. In our case, we have Release configurations that remove the debug attribute from the web.config's compilation section. Below is a screenshot of an example and Visual Studio's dropdown list of build configurations.

NOTE: Also make sure your Platform is correct along with the configuration. In my case, Dev.Debug|Mixed Platforms does not correctly build the solution but Dev.Debug|Any CPU will.

Answer 2

I know this is not the OPs issue, but I had this happen on a project. The solution had multiple MVC projects and the wrong project was set as startup.

I had also set the configuration of the project(s) to just start process/debugger and not open a new browser window.

So on the surface it looks as if the debugger is starting up, but it does so for the wrong process. So check that and keep in mind that you can attach to multiple processes also.

Silly mistake that left me scratching my head for about 30 minutes.

Answer 3

The issue was resolved by unchecking the

Properties > Build > Optimize Code

setting on the web page properties screen (under General).

Answer 4

If none of the above work, double-check your code. Sometimes the reason why the breakpoint appears to not be hitting is due to the block of code containing the breakpoint is not being executed for sometimes inadvertant reasons.

For example, forgetting the "Handles Me.Load" has gotten me a few times when copying and pasting code:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)
    --this block of code will not execute
    End Sub 

vs

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    --this block executes
    End Sub

Answer 5

Go to Visual Studio Menu:

Debug -> Attach to Process

And then click the Select button, as in the image below:

Then make sure the "Automatically determine the type of code to debug" option is selected, like this:

Answer 6

In my scenario, I've got an MVC app and WebAPI in one solution, and I'm using local IIS (not express).

I also set up the sites in IIS as real domains, and edited my host file so that I can type in the real domain and everything works. I also noticed 2 things:

1. The MVC code debugging was working perfectly.

2. Attaching to process worked perfectly too. Just when I was debugging it didn't hit the breakpoint in my API.

This was the solution for me:

Right click webapi project > properties > Web > Project URL

By default it points to localhost, but since I set up the site in IIS, I forgot to change the URL to the website domain (i.e. instead of locahost, it should say http://{domain-name}/).