System.Tests.StringTests.Concat_String C# (CSharp) Method

        public static void Concat_String(string[] values, string expected)
        {
            Action<string> validate = result =>
            {
                Assert.Equal(expected, result);
                if (result.Length == 0)
                {
                    Assert.Same(string.Empty, result);
                }
            };

            if (values.Length == 2)
            {
                validate(string.Concat(values[0], values[1]));
            }
            else if (values.Length == 3)
            {
                validate(string.Concat(values[0], values[1], values[2]));
            }
            else if (values.Length == 4)
            {
                validate(string.Concat(values[0], values[1], values[2], values[3]));
            }

            validate(string.Concat(values));
            validate(string.Concat((IEnumerable<string>)values));
            validate(string.Concat<string>((IEnumerable<string>)values)); // Call the generic IEnumerable<T>-based overload
        }