How can I set my null-checking method to satisfy the warning "possible 'null' assignment to entity marked with 'NotNull' attribute"

Permanently deleted user

Created October 26, 2015 21:30

I have an overload function for string to make it slightly easier to check if a string has been populated.

    public static bool IsNullOrWhitespace(this string source)
    {
        return string.IsNullOrWhiteSpace(source);
    }

When I use this on variable, then use that variable as a [NotNull] paramater in a method call, I get the warning "possible 'null' assignment to entity marked with 'NotNull' attribute." Directly calling string.IsNullOrWhiteSpace(source) keeps the warning from showing up. Is there a way I can tell ReSharper that my method is a valid check for null?

4 comments

Richard Deeming

Created October 29, 2015 13:07

You need to add the ContractAnnotationAttribute to your method:

 [ContractAnnotation("source:null => true")]
public static bool IsNullOrWhitespace(this string source)
{
    return string.IsNullOrWhiteSpace(source);
}

Permanently deleted user

Created October 29, 2015 16:19

That did the trick, Richard. Thanks!

Jeff Ward

Created July 20, 2022 17:20

Is there any way to do this with Null Checking Patterns so that we are not dependent on annotations?

Maria Pleskunina

Created July 25, 2022 10:25

I'll duplicate Richard's answer here: https://resharper-support.jetbrains.com/hc/en-us/community/posts/6722297112594/comments/6729176732050

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