CA2248: Provide correct enum argument to Enum.HasFlag

Property	Value
Rule ID	CA2248
Title	Provide correct enum argument to Enum.HasFlag
Category	Usage
Fix is breaking or non-breaking	Non-breaking
Enabled by default in .NET 9	As suggestion

Cause

The enum type passed as an argument to the HasFlag method call is different from the calling enum type.

Rule description

The Enum.HasFlag method expects the enum argument to be of the same enum type as the instance on which the method is invoked. If these are different enum types, an unhandled exception will be thrown at run time.

How to fix violations

To fix violations, use the same enum type on both the argument and the caller:

public class C
{
    [Flags]
    public enum MyEnum { A, B, }

    [Flags]
    public enum OtherEnum { A, }

    public void Method(MyEnum m)
    {
        m.HasFlag(OtherEnum.A); // Enum types are different, this call will cause an `ArgumentException` to be thrown at run time

        m.HasFlag(MyEnum.A); // Valid call
    }
}

When to suppress warnings

Do not suppress violations from this rule.