public void TestJoin() { System.Collections.Generic.List <int> intList = new System.Collections.Generic.List <int>() { 1, 2, 3, 4, 5, 6, 7, 8, 9 }; Assert.AreEqual("1,2,3,4,5,6,7,8,9", intList.Join()); Assert.AreEqual("123456789", intList.Join("")); Assert.AreEqual("1__2__3__4__5__6__7__8__9", intList.Join("__")); string[] strArray = new string[] { "1", "2", "3", "4", "5", "6", "7", "8", "9" }; Assert.AreEqual("1,2,3,4,5,6,7,8,9", strArray.Join()); Assert.AreEqual("123456789", strArray.Join("")); Assert.AreEqual("1__2__3__4__5__6__7__8__9", strArray.Join("__")); bool[] nullArray = null; Assert.Throws(typeof(System.ArgumentException), () => strArray.Join(null)); Assert.Throws(typeof(System.ArgumentException), () => nullArray.Join()); }