Debug assertion failed

You need to run your code under the debugger, and when the assertion fails, you then look at the information that is provided: the assertion message and the call stack. The latter tells you where the problem was detected, and the "chain" of functions that was called to get to that point. Somewhere in that chain will we your code - so start with there and look at what system functions / classes / delegates you are calling and what parameters you are passing. Something is wrong, and you will probably need to put a breakpoint on the call and run it again to start looking for what.

Sorry, but we can't help you - time to start learning a new skill: debugging.

The assertation is a failure of the program which is using that dll. So you need to debug your app and remove that bug.

Take a First look at the Visual Studio Debugger to better understand that tool and its features.
Find the place where the assert occurs and than figure out why it happens. Often it is an invalid handle in startup or exit code.