I'm attempting to pass Guid.Empty into my unit test:

```
[TestCase(null)]
[TestCase(Guid.Empty)]
public void When_AccountGuid_IsNullOrEmpty_AddError_Is_Invoked(Guid? accountGuid)
{

}

```

However the compiler is complaining:

> 
> An attribute argument must be a constant expression, typeof expression
>  or array creation expression of an attribute parameter type
> 
> 
> 

**How do I pass Guid.Empty into my unit test method?**

I've also tried to factor it out by declaring it as a private member in the class, with the same compiler error:

```
        private static Guid _emptyGuid = Guid.Empty;
        [TestCase(null)]
        [TestCase(_emptyGuid)]
        public void When_AccountGuid_IsNullOrEmpty_AddError_Is_Invoked(Guid? accountGuid)
        {

        }

```