Question

let’s have this code :

class MyList : IEnumerable, IEnumerator
{
    int[] A = { 1, 2, 3, 4, 5 };
    int i = -1;

    #region IEnumerator Members

    public object Current
    {
        get { return A[i]; }
    }

    public bool MoveNext()
    {
        i++;
        return i < 5;
    }

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

    #endregion

    #region IEnumerable Members

    public IEnumerator GetEnumerator()
    {
        return (IEnumerator)this;
    }

    #endregion
}

And In Main Method :

MyList list = new MyList();
foreach (int i in list)
{
    Console.WriteLine(i);
}

foreach (int i in list)
{
    Console.WriteLine(i);
}

Why the second foerach doesn’t work ?? and the “i” doesn’t initialize again ??

Is that true : Reset method should be called automatically before foreach is executed ??

why it doesn’t call here ??

Answer 1

The IEnumerable and IEnumerator should generally be separate classes, and except in the case of enumerators that always return empty or always return the same item, the GetEnumerator method must always return a new instance of an IEnumerator.

There isn’t much point to IEnumerator.Reset; for-each loops don’t use it, and consumers of an IEnumerable/IEnumerator can’t use it unless they know what the enumerable type is, in which case they could use the actual type rather than the interface.