c# - Object reference not set to an instance of an object

This simply means you are using an object that is
null. Accessing a member on null is
never valid.

I'm not sure which line is causing
the error. Is it the one that says "Primary Key"? If so, could employees be
null? It should be extremely trivial to find out using the
debugger.

If needed, check for
null before using the object to prevent this
error.