This answer and the comments added to it show a way to disable several compiler warnings using #pragma directives.
Why would one want to do that? Usually the warnings are there for a reason, and I've always felt that they're good reasons. Is there any "valid case" where warnings should be disabled? Right now I can't think of any, but maybe that's just me.
Best Answer
I've only ever had one situation where I disabled a warning. I consider warnings errors so I wouldn't normally release with warnings. However, while developing an API at a customers I faced the issue that a method that was needed in a migration phase by one application and that no other should ever use had to be included in the library.
The best way I could find to tell all users of the API that they shouldn't call this method was to mark it obsolete. That, however, meant that the one valid use case was marked as a compile warning.
Eric Lippert has written a few posts about warnings where you'll find information about how the compiler team thinks about warnings.
Internal fields of Internal types
Unused using directives are not marked with warnings