Unexpected Behaviour on Error

[rbulph]

Normally if there's an error in my code the debugger stops at that error and tells me about it. But a recent null reference error in a sub called from the Paint event of a Picture box did not cause the debugger to stop execution but to abort the drawing and colour the picturebox white with a red border and red diagonal lines. The following message appeared in the Immediate Window:

"A first chance exception of type 'System.NullReferenceException' occurred in Res Ipsa.exe"

This really threw me as I originally thought that somehow I was drawing this pattern. But anyway does anyone know why it did this rather than stop execution in the normal way?

 

[mandelbrot]

Have you got any Try Catch blocks in your code?

 

[rbulph]

Have you got any Try Catch blocks in your code?

Not that can be accessed from the code that is called on the Paint event.

 

[mandelbrot]

Ok - can you post your paint event?

 

[mskeel]

Sounds like you are passing something into the PictureBox's paint method either directly or indirectly that it either doesn't expect or doesn't want and the PictureBox is throwing an exception that you aren't handling. Because the exception is thrown from so far down the call chain from within the Framework, you get errors that are a little different than errors caused directly by you, say in your form or something. Don't get me wrong, you are still causing the error, it's just not happening until later.

Could you post up some code around where the error occurs?