How to show “if” condition on a sequence diagram?

Question

I was wondering, how can one represent \"if\" statement on a sequence diagram?

if (somethingShouldBeDone) {
       // Do it
} else {
       // D         


        

Answer 1

In Visual Studio UML sequence this can also be described as fragments which is nicely documented here: https://msdn.microsoft.com/en-us/library/dd465153.aspx