System.ComponentModel.MaskedTextProvider.this C# (CSharp) Method

        public char this[int index]
        {
            get
            {
                if (index < 0 || index >= _testString.Length)
                {
                    throw new IndexOutOfRangeException(index.ToString(CultureInfo.CurrentCulture));
                }

                return _testString[index];
            }
        }