Write Methods and Unit Tests

At the moment I'm programming some Unit Tests in C# for my WebService. So the read methods all easy to do but now I want to test my write functions.

When I start my tests for the write methods I always get a new database entry. Is there a way to run the test function get the result and after that the test function do a rollback so the new entry is no longer in the db?

Or how do you test write functions?

Thanks for help