How do I remedy "The breakpoint will not currently be hit. No symbols have been loaded for this document." warning?

A C# desktop application (on the Visual Studio Express edition) worked, but then it didn't work 5 seconds later.

I tried the following:

* Ensure debug configuration, debug flag, and full debug information are set on all assemblies.
* Delete all bin and obj folders and all DLL files related to the project from my entire machine.
* Recreate projects causing the problem from scratch.
* Reboot.

I have two Windows Forms projects in the solution. One of them loads the debug information, one doesn't. They both refer to the assembly I'm trying to get debug information on in exactly the same way in the project file. Any ideas?

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I want to add here, mostly for myself when I come back to review this question, that symbols are not loaded until the assembly is loaded, and the assembly is not loaded until it is needed. If the breakpoint is in a library that is only used in one function in your main assembly, the symbols will not be loaded (and it will show the breakpoint as not being hit) until that function is called.

You need to enable "Generate debug info" in compiler settings

I ran into this problem trying to debug the background agent of a WP7 app. As it turned out, this debugging issue was only a symptom of the real problem: My background agent wasn't running at all in debug mode. I had followed the following guide on how to implement a background agent:

[To see links please register here]

... but forgot to add

#define DEBUG_AGENT

which meant that my agent was never actually being started in debugging mode. Once this line was added, the problem that this thread is about went away.

For an ASP.Net application, check the properties of the site, ASP.NET tab. Ensure that the correct ASP.NET version is selected.

Yet Another solution for some cases where this error occurs: check your **Build Action**.

I had this issue in an asp.net MVC3 project; one of my controllers had for some unknown reason it's Build Action set to EntityDeploy although it should have been **Compile**.

I've done the clean and rebuild thing. That didn't work (it usually does).
Now, I am attaching to w3wp before calling through the service, then let it call the service once, hit another breakpoint, then I change the point of execution so that it will run the same line (calling the service) again, then it actually stops at my breakpoint inside the service method.