Question

I’m trying to write my own (simple) implementation of List. This is what I did so far:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace provaIEnum
{
    class MyList<T> : IEnumerable<T>
    {
        private T[] _array;
        public int Count { get; private set; }

        public MyList() { /* ... */ }
        public void Add(T element) { /* ... */ }

        // ...

        public IEnumerator<T> GetEnumerator()
        {
            for (int i = 0; i < Count; i++)
                yield return _array[i];
        }
    }

I’m getting an error about GetEnumerator though:

‘provaIEnum.Lista’ does not implement interface member
‘System.Collections.IEnumerable.GetEnumerator()’.
‘provaIEnum.Lista.GetEnumerator()’ cannot implement
‘System.Collections.IEnumerable.GetEnumerator()’ because it does not
have the matching return type of ‘System.Collections.IEnumerator’.

I’m not sure if I understand what VS’s trying to tell me and I have no idea how to fix it.

Thanks for your time

Answer 1

Since IEnumerable<T> implements IEnumerable you need to implement this interface as well in your class which has the non-generic version of the GetEnumerator method. To avoid conflicts you could implement it explicitly:

IEnumerator IEnumerable.GetEnumerator()
{
    // call the generic version of the method
    return this.GetEnumerator();
}

public IEnumerator<T> GetEnumerator()
{
    for (int i = 0; i < Count; i++)
        yield return _array[i];
}