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

        public static void Join_StringArray(string separator, string[] values, int startIndex, int count, string expected)
        {
            if (startIndex + count == values.Length && count != 0)
            {
                Assert.Equal(expected, string.Join(separator, values));

                var iEnumerableStringOptimized = new List<string>(values);
                Assert.Equal(expected, string.Join(separator, iEnumerableStringOptimized));
                Assert.Equal(expected, string.Join<string>(separator, iEnumerableStringOptimized)); // Call the generic IEnumerable<T>-based overload

                var iEnumerableStringNotOptimized = new Queue<string>(values);
                Assert.Equal(expected, string.Join(separator, iEnumerableStringNotOptimized));
                Assert.Equal(expected, string.Join<string>(separator, iEnumerableStringNotOptimized));

                var iEnumerableObject = new List<object>(values);
                Assert.Equal(expected, string.Join(separator, iEnumerableObject));

                // Bug/Documented behavior: Join(string, object[]) returns "" when the first item in the array is null
                if (values.Length == 0 || values[0] != null)
                {
                    var arrayOfObjects = (object[])values;
                    Assert.Equal(expected, string.Join(separator, arrayOfObjects));
                }
            }
            Assert.Equal(expected, string.Join(separator, values, startIndex, count));
        }