我不记得是谁给我的了，但它很好用。我快速测试了几种将枚举类型分成组的方法。用法是这样的…

List<string> Divided = Source3.Chunk(24).Select(Piece => string.Concat<char>(Piece)).ToList();

扩展代码看起来像这样…

#region Chunk Logic
private class ChunkedEnumerable<T> : IEnumerable<T>
{
    class ChildEnumerator : IEnumerator<T>
    {
        ChunkedEnumerable<T> parent;
        int position;
        bool done = false;
        T current;


        public ChildEnumerator(ChunkedEnumerable<T> parent)
        {
            this.parent = parent;
            position = -1;
            parent.wrapper.AddRef();
        }

        public T Current
        {
            get
            {
                if (position == -1 || done)
                {
                    throw new InvalidOperationException();
                }
                return current;

            }
        }

        public void Dispose()
        {
            if (!done)
            {
                done = true;
                parent.wrapper.RemoveRef();
            }
        }

        object System.Collections.IEnumerator.Current
        {
            get { return Current; }
        }

        public bool MoveNext()
        {
            position++;

            if (position + 1 > parent.chunkSize)
            {
                done = true;
            }

            if (!done)
            {
                done = !parent.wrapper.Get(position + parent.start, out current);
            }

            return !done;

        }

        public void Reset()
        {
            // per http://msdn.microsoft.com/en-us/library/system.collections.ienumerator.reset.aspx
            throw new NotSupportedException();
        }
    }

    EnumeratorWrapper<T> wrapper;
    int chunkSize;
    int start;

    public ChunkedEnumerable(EnumeratorWrapper<T> wrapper, int chunkSize, int start)
    {
        this.wrapper = wrapper;
        this.chunkSize = chunkSize;
        this.start = start;
    }

    public IEnumerator<T> GetEnumerator()
    {
        return new ChildEnumerator(this);
    }

    System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }

}
private class EnumeratorWrapper<T>
{
    public EnumeratorWrapper(IEnumerable<T> source)
    {
        SourceEumerable = source;
    }
    IEnumerable<T> SourceEumerable { get; set; }

    Enumeration currentEnumeration;

    class Enumeration
    {
        public IEnumerator<T> Source { get; set; }
        public int Position { get; set; }
        public bool AtEnd { get; set; }
    }

    public bool Get(int pos, out T item)
    {

        if (currentEnumeration != null && currentEnumeration.Position > pos)
        {
            currentEnumeration.Source.Dispose();
            currentEnumeration = null;
        }

        if (currentEnumeration == null)
        {
            currentEnumeration = new Enumeration { Position = -1, Source = SourceEumerable.GetEnumerator(), AtEnd = false };
        }

        item = default(T);
        if (currentEnumeration.AtEnd)
        {
            return false;
        }

        while (currentEnumeration.Position < pos)
        {
            currentEnumeration.AtEnd = !currentEnumeration.Source.MoveNext();
            currentEnumeration.Position++;

            if (currentEnumeration.AtEnd)
            {
                return false;
            }

        }

        item = currentEnumeration.Source.Current;

        return true;
    }

    int refs = 0;

    // needed for dispose semantics 
    public void AddRef()
    {
        refs++;
    }

    public void RemoveRef()
    {
        refs--;
        if (refs == 0 && currentEnumeration != null)
        {
            var copy = currentEnumeration;
            currentEnumeration = null;
            copy.Source.Dispose();
        }
    }
}
/// <summary>Speed Checked.  Works Great!</summary>
public static IEnumerable<IEnumerable<T>> Chunk<T>(this IEnumerable<T> source, int chunksize)
{
    if (chunksize < 1) throw new InvalidOperationException();

    var wrapper = new EnumeratorWrapper<T>(source);

    int currentPos = 0;
    T ignore;
    try
    {
        wrapper.AddRef();
        while (wrapper.Get(currentPos, out ignore))
        {
            yield return new ChunkedEnumerable<T>(wrapper, chunksize, currentPos);
            currentPos += chunksize;
        }
    }
    finally
    {
        wrapper.RemoveRef();
    }
}
#endregion

使用正则表达式和Linq:

List<string> groups = (from Match m in Regex.Matches(str, @"\d{4}")
                       select m.Value).ToList();

我觉得这样更有可读性，但这只是个人观点。它也可以是一行代码:)。

在多芬和康他汀的答案组合中……

static IEnumerable<string> WholeChunks(string str, int chunkSize) {
    for (int i = 0; i < str.Length; i += chunkSize) 
        yield return str.Substring(i, chunkSize);
}

这将适用于所有可以被分割成大量块的字符串，否则将抛出异常。

如果你想支持任意长度的字符串，你可以使用下面的代码:

static IEnumerable<string> ChunksUpto(string str, int maxChunkSize) {
    for (int i = 0; i < str.Length; i += maxChunkSize) 
        yield return str.Substring(i, Math.Min(maxChunkSize, str.Length-i));
}

然而，OP明确表示他不需要这个;它有点长，很难读，稍微慢一点。本着KISS和YAGNI的精神，我选择第一个选项:它可能是最有效的实现，而且非常简短、可读，而且重要的是，它会对不符合规范的输入抛出异常。

六年后o_O

仅仅因为

    public static IEnumerable<string> Split(this string str, int chunkSize, bool remainingInFront)
    {
        var count = (int) Math.Ceiling(str.Length/(double) chunkSize);
        Func<int, int> start = index => remainingInFront ? str.Length - (count - index)*chunkSize : index*chunkSize;
        Func<int, int> end = index => Math.Min(str.Length - Math.Max(start(index), 0), Math.Min(start(index) + chunkSize - Math.Max(start(index), 0), chunkSize));
        return Enumerable.Range(0, count).Select(i => str.Substring(Math.Max(start(i), 0),end(i)));
    }

or

    private static Func<bool, int, int, int, int, int> start = (remainingInFront, length, count, index, size) =>
        remainingInFront ? length - (count - index) * size : index * size;

    private static Func<bool, int, int, int, int, int, int> end = (remainingInFront, length, count, index, size, start) =>
        Math.Min(length - Math.Max(start, 0), Math.Min(start + size - Math.Max(start, 0), size));

    public static IEnumerable<string> Split(this string str, int chunkSize, bool remainingInFront)
    {
        var count = (int)Math.Ceiling(str.Length / (double)chunkSize);
        return Enumerable.Range(0, count).Select(i => str.Substring(
            Math.Max(start(remainingInFront, str.Length, count, i, chunkSize), 0),
            end(remainingInFront, str.Length, count, i, chunkSize, start(remainingInFront, str.Length, count, i, chunkSize))
        ));
    }

AFAIK所有的边缘情况都处理好了。

Console.WriteLine(string.Join(" ", "abc".Split(2, false))); // ab c
Console.WriteLine(string.Join(" ", "abc".Split(2, true))); // a bc
Console.WriteLine(string.Join(" ", "a".Split(2, true))); // a
Console.WriteLine(string.Join(" ", "a".Split(2, false))); // a

这样写一行代码怎么样?

List<string> result = new List<string>(Regex.Split(target, @"(?<=\G.{4})", RegexOptions.Singleline));

对于这个正则表达式，最后一个块是否小于4个字符并不重要，因为它只查看它后面的字符。

我知道这不是最有效的解决方案，但我不得不把它扔出去。

static IEnumerable<string> Split(string str, int chunkSize)
{
   IEnumerable<string> retVal = Enumerable.Range(0, str.Length / chunkSize)
        .Select(i => str.Substring(i * chunkSize, chunkSize))

   if (str.Length % chunkSize > 0)
        retVal = retVal.Append(str.Substring(str.Length / chunkSize * chunkSize, str.Length % chunkSize));

   return retVal;
}

它正确地处理不能被chunkSize整除的输入字符串长度。

请注意，可能需要额外的代码来优雅地处理边缘情况(null或空输入字符串，chunkSize == 0)。