System.Collections.Specialized.OrderedDictionary.RemoveAt C# (CSharp) Method

        public void RemoveAt(int index)
        {
            if (_readOnly)
            {
                throw new NotSupportedException(SR.OrderedDictionary_ReadOnly);
            }
            if (index >= Count || index < 0)
            {
                throw new ArgumentOutOfRangeException(nameof(index));
            }
            object key = ((DictionaryEntry)objectsArray[index]).Key;
            objectsArray.RemoveAt(index);
            objectsTable.Remove(key);
        }

		private void Common (OrderedDictionary od)
		{
			Assert.IsNotNull (od.GetEnumerator (), "GetEnumerator");
			Assert.AreEqual (0, od.Count, "Count-0");
			Assert.IsFalse (od.IsReadOnly, "IsReadOnly");
			od.Add ("a", "1");
			Assert.AreEqual (1, od.Count, "Count-1");
			od["a"] = "11";
			Assert.AreEqual ("11", od["a"], "this[string]");
			od[0] = "111";
			Assert.AreEqual ("111", od[0], "this[int]");

			DictionaryEntry[] array = new DictionaryEntry[2];
			od.CopyTo (array, 1);

			Assert.AreEqual ("111", ((DictionaryEntry)array[1]).Value, "CopyTo");
			Assert.AreEqual (1, od.Keys.Count, "Keys");
			Assert.AreEqual (1, od.Values.Count, "Values");
			Assert.IsTrue (od.Contains ("a"), "Contains(a)");
			Assert.IsFalse (od.Contains ("111"), "Contains(111)");

			od.Insert (0, "b", "2");
			Assert.AreEqual (2, od.Count, "Count-2");
			od.Add ("c", "3");
			Assert.AreEqual (3, od.Count, "Count-3");

			OrderedDictionary ro = od.AsReadOnly ();

			od.RemoveAt (2);
			Assert.AreEqual (2, od.Count, "Count-4");
			Assert.IsFalse (od.Contains ("c"), "Contains(c)");

			od.Remove ("b");
			Assert.AreEqual (1, od.Count, "Count-5");
			Assert.IsFalse (od.Contains ("b"), "Contains(b)");

			od.Clear ();
			Assert.AreEqual (0, od.Count, "Count-6");

			Assert.IsTrue (ro.IsReadOnly, "IsReadOnly-2");
			// it's a read-only reference
			Assert.AreEqual (0, od.Count, "Count-7");
		}