How to stop Visual Studio debugging so sql database changes not commit?

I think the best thing is to use TransactionScope class for this.

Just wrap your db calls inside

 using (TransactionScope scope = new TransactionScope())
{
   // Invoke your database calls
   scope.Complete(); // Put a break point here and stop the program when the break point is hit.
}

I usually kill the w3wp.exe process using Process Explorer. Alternatively, you can drag and drop the "yellow mark" in the debugger to a point after the commit so that the commit is skipped. I also sometimes set a variable to null and induce a crash that way.

If you want to throw an exception, you can do it using Immediate Window, after hitting breakpoint.

The problem is, you can not use in Immediate Window something like:

throw new ApplicationException("Forced exception");

But you can create the method, and then launch it from Immediate Window

public static void ForceAnException()
{
    throw new ApplicationException("Forced exception");
}

In immediate window:

ForceAnException();

EDIT:

So maybe try this:

var throwEx = false;
if(throwEx) ForceAnException();

And change in immediate window throwEx to true, before condition is checked...it should work...