C#高级程序设计（七）——迭代

.NET使用IEnumerator接口和IEnumerable接口（以及它们的泛型版本）实现迭代器模式，迭代是LINQ的核心。
接口定义如下：
[csharp]
public inte易做图ce IEnumerable
{
    IEnumerator GetEnumerator();
}

public inte易做图ce IEnumerator
{
    object Current { get; }
    bool MoveNext();
    void Reset();
}

public inte易做图ce IEnumerable<out T> : IEnumerable
{
    IEnumerator<T> GetEnumerator();
}

public inte易做图ce IEnumerator<out T> : IDisposable, IEnumerator
{
    T Current { get; }
}

一、C#1实现迭代方式
C#1通过实现接口实现迭代，下面是一个例子，可以指定起始的顺序来迭代集合，其中的一些注意点在注释中有所体现。
[csharp]
public class IterationSample : IEnumerable<string>
    {
        string[] values;
        int startingPoint;

        public IterationSample(string[] values, int startingPoint)
        {
            this.values = values;
            this.startingPoint = startingPoint;
        }
        public IEnumerator<string> GetEnumerator()
        {
            // This is important to return a new instance of iterator
            // so that each foreach loop will have its own iterator.
            return new IterationSampleIterator(this);
        }

        // Class that implement IEnumerable<T> must also implement IEnumerable,
        // here is a workaround to implement GetEnumerator method that defined
        // in both IEnumerable<T> and IEnumerable.
        IEnumerator IEnumerable.GetEnumerator()
        {
            return GetEnumerator();
        }

        // Inner class can access to private members of its parent class.
        class IterationSampleIterator : IEnumerator<string>
        {
            IterationSample parent;
            int position;

            internal IterationSampleIterator(IterationSample parent)
            {
                this.parent = parent;
                position = -1;
            }

            public bool MoveNext()
            {
                if (position != parent.values.Length)
                {
                    position++;
                }

                return position < parent.values.Length;
            }

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

            public string Current
            {
                get
                {
                    if (position == -1 ||
                    position == parent.values.Length)
                    {
                        throw new InvalidOperationException();
                    }
                    int index = position + parent.startingPoint;
                    index = index % parent.values.Length;
                    return parent.values[index];
                }
            }

            public void Reset()
            {
                position = -1;
            }

            public void Dispose()
            {
            }
        }&

补充：软件开发 , C# ,