What is the smoothest, most appealing syntax you've found for asserting parameter correctness in c#?

Question

A common problem in any language is to assert that parameters sent in to a method meet your requirements, and if they don\'t, to send nice, informative error messages. This

Answer 1

My preference would be to just evaluate the condition and pass the result rather than passing an expression to be evaluated and the parameter on which to evaluate it. Also, I prefer to have the ability to customize the entire message. Note that these are simply preferences -- I'm not saying that your sample is wrong -- but there are some cases where this is very useful.

Helper.Validate( firstName != null || !string.IsNullOrEmpty(directoryID),
                 "The value for firstName cannot be null if a directory ID is not supplied." );