Unable to pass string array, NUnit Test

Folks,

Like many of you , I want to pass different test parameters using NUnit Test.

I can pass integer array, no problem, but when I pass string array it does not work.

[TestCase(
                new[] {"ACCOUNT", "SOCIAL"})]
            public void Get_Test_Result(string[] contactTypes)
            {  ... }

Error 3 An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type ... \ContactControllerTests.cs 78 13 UnitTests

It works when I use string array as a second argument.

  [TestCase(0,
            new[] {"ACCOUNT", "SOCIAL"})]
        public void Get_Test_Result(int dummyNumber, string[] contactTypes)
        {  ... }

So what is the reason?