C28221

The new home for Visual Studio documentation is Visual Studio 2017 Documentation on docs.microsoft.com.

The latest version of this topic can be found at C28221.

warning C28221: String expression expected for the parameter in the annotation

This warning indicates that a parameter to an annotation is expected to be a string, and some other type was encountered. This usually indicates an incorrectly coded annotation macro and is not expected to be seen in normal use.