How can I show that a method will never return nul

Question

I have a method which never returns a null object. I want to make it clear so that users of my API don't have to write code like this:

if(Getxyz() != null)
{
  // do stuff
}

How can I show this intent?

Answer 1

Document it and provide the source code.

Answer 2

Either document it well (maybe with .NET standard documentation system) or you have to use some Contract API. Here are some: http://geekswithblogs.net/Podwysocki/archive/2008/01/22/118770.aspx http://www.codeproject.com/KB/cs/designbycontract.aspx

Answer 3

I like to think of it the other way around: if my function could return a null value I better make sure that the function's user knows about it.