How to implement IEnumerable<T> with GetEnumerator()? [duplicate]

Question

I would like my type to implement IEnumerable<string> . I tried to follow C# in a Nutshell, but something went wrong:

public class Simulation : IEnumerable<string>
{
    private IEnumerable<string> Events()
    {
        yield return "a";
        yield return "b";
    }

    public IEnumerator<string> GetEnumerator()
    {
        return Events().GetEnumerator();
    }
}

But I get the build error

Error 1 'EventSimulator.Simulation' does not implement interface member 'System.Collections.IEnumerable.GetEnumerator()'. 'EventSimulator.Simulation.GetEnumerator()' cannot implement 'System.Collections.IEnumerable.GetEnumerator()' because it does not have the matching return type of 'System.Collections.IEnumerator'.

Answer 1

You're missing IEnumerator IEnumerable.GetEnumerator():

public class Simulation : IEnumerable<string>
{
    private IEnumerable<string> Events()
    {
        yield return "a";
        yield return "b";
    }

    public IEnumerator<string> GetEnumerator()
    {
        return Events().GetEnumerator();
    }

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

Answer 2

IEnumerable requires that you implement both the typed and generic method.

In the community section of the msdn docs it explains why you need both. (For backwards compatibility is the reason given essentially).