Debugging in Class Library

[rbulph]

I have a project with a class library, both open in the IDE. Why do I find that errors in the class library do not cause the debugger to stop execution at the relevant line, but instead to go right the way up the call stack back to the project, and exit the orginal procedure? This naturally makes it hard to track down where an error is occurring.

 

I have tried recreating this with a simple project, but I do not get the same problems there. In both the simple project and the one I am developing the Debug tab of the Project properties has "Enable the Visual Studio Hosting Process" checked, so there is no difference with that that might be causing it.