System.Collections.Stack.StackEnumerator.MoveNext C# (CSharp) Method

            public virtual bool MoveNext()
            {
                bool retval;
                if (_version != _stack._version) throw new InvalidOperationException(SR.InvalidOperation_EnumFailedVersion);
                if (_index == -2)
                {  // First call to enumerator.
                    _index = _stack._size - 1;
                    retval = (_index >= 0);
                    if (retval)
                        _currentElement = _stack._array[_index];
                    return retval;
                }
                if (_index == -1)
                {  // End of enumeration.
                    return false;
                }

                retval = (--_index >= 0);
                if (retval)
                    _currentElement = _stack._array[_index];
                else
                    _currentElement = null;
                return retval;
            }