Code Inspection: Replace built-in type reference with a CLR type name or a keyword
The C# type keywords and .NET Framework type names are interchangeable with built-in C# types. If you prefer to stick to one or another style for built-in type names, ReSharper can help you maintain your preference.
ReSharper checks all built-in type references for compliance with your preferences and if they do not comply it highlights such references and suggests the corresponding quick-fix or fix in scope. Default ReSharper's preferences say that the C# keywords are preferred.
For more information about configuring and enforcing your preferences for C# built-in type references, see Code Syntax Style: Built-In Type References.