CharEnumerator.cs

using System.Collections;
using System.Collections.Generic;
using System.Runtime.InteropServices;

namespace System
{
    [Serializable]
    [ComVisible(true)]
    public sealed class CharEnumerator : IEnumerator, ICloneable, IEnumerator<char>, IDisposable
    {
        private string str;

        private int index;

        private char currentElement;

        object IEnumerator.Current
        {
            get
            {
                if (index == -1)
                {
                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumNotStarted"));
                }
                if (index >= str.Length)
                {
                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumEnded"));
                }
                return currentElement;
            }
        }

        public char Current
        {
            get
            {
                if (index == -1)
                {
                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumNotStarted"));
                }
                if (index >= str.Length)
                {
                    throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_EnumEnded"));
                }
                return currentElement;
            }
        }

        internal CharEnumerator(string str)
        {
            this.str = str;
            index = -1;
        }

        public object Clone()
        {
            return MemberwiseClone();
        }

        public bool MoveNext()
        {
            if (index < str.Length - 1)
            {
                index++;
                currentElement = str[index];
                return true;
            }
            index = str.Length;
            return false;
        }

        public void Dispose()
        {
            if (str != null)
            {
                index = str.Length;
            }
            str = null;
        }

        public void Reset()
        {
            currentElement = '\0';
            index = -1;
        }
    }
}