To test method excecution time you can use Stopwatch Class.
Also there is built-in profiler in VS 2013 under ANALYZE => Profiler menu. I don't remember in which version of VS it has been added, but I think it is there in VS 2012. So you can start profiling, use your application for a while and then check what operations took more time to excecute.
UPDATE: VS 2017 nowVisual Studio shows execution time in milliseconds for each line or when Run To Click is used during debugging session, which can give some rough idea of the statement execution time:
For simple measurements Stopwatch class can be a handy option too.
For more advanced scenarios there is a built-in profiler in Visual Studio Analyze CPU usage without debugging in the Performance Profiler.
And for precise performance measurements there is an excellent and powerful tool BenchmarkDotNet.
