C#: How to Implement and use a NotNull and CanBeNull attribute

Question

I want to let programmers and myself know that a method does not want null and if you do send null to it anyways, the result will not be pretty.

Answer 1

This can be done either with AOP, whereby an Advice verifies at run-time whether a method parameter is null and whether nulls are allowed. See PostSharp and Spring.NET for AOP.

As for ReSharper, see Annotated Framework:

We have analyzed a great share of .NET Framework Class Library, as well as NUnit Framework, and annotated it through external XML files, using a set of custom attributes from the JetBrains.Annotations namespace, specifically:

• StringFormatMethodAttribute (for methods that take format strings as parameters)
• InvokerParameterNameAttribute (for methods with string literal arguments that should match one of caller parameters)
• AssertionMethodAttribute (for assertion methods)
• AssertionConditionAttribute (for condition parameters of assertion methods)
• TerminatesProgramAttribute (for methods that terminate control flow)
• CanBeNullAttribute (for values that can be null)
• NotNullAttribute (for values that can not be null)