Why would the debugger not be stopping at a breakpoint in my ASP.NET application?

Question

I'm trying to debug a large ASP.NET application.

I set a breakpoint on the first line in Page_Load in Default.aspx.cs.

When I start the application, my breakpoint briefly turns into a red round outline with an exclamation in it, then turns back into a regular breakpoint, then the application starts without ever stopping at my breakpoint.

MSDN tells me that this symbol means "the breakpoint location has not been loaded". So how can I get the breakpoint location to load? It was working a couple weeks ago. What kinds of things could cause a breakpoint to "not be loaded"?

What can I do so that the debugger stops at my breakpoints again?

Addendum:

I still can't get debugging to work by pressing F5, but I can start the website, then do debug/attach-process to get into debugging mode. If anyone knows why this would work but when I press F5 it would not work (the debugging buttons don't even show up on F5), any ideas would be welcome.

Answer 1

Try doing a full rebuild on the application. Pay attention that it's in the "Debug" configuration.

As far as I understand (but I'm not an expert in these things), this can happen when the debug info files (.PDB) are out of sync with the real compiled thing.