Implement IEnumerable for a collection class?

Question

I want to understand this topic and not just be able to throw down the syntax. I have a collection class called IGroupNode, which can take in a maximum of 8 children ISceneNodes.

internal class GroupNode : IGroupNode
{
    public string Name
    {
        get;
        private set;
    }

    const int NumberOfChildren = 8;
    #region Member variables
    private IList<ISceneNode> children = new List<ISceneNode>(NumberOfChildren);
    #endregion

    public IEnumerable<ISceneNode> GetEnumerator()
    {
        //?
    }

As you can probably tell, it is a very simple collection class based off of a list. How can I make the implementation of IEnumerable here simply return the internal container’s enumerator? I am not sure how to do this in this very easy case.

Now I am running into trouble with this problem:

'Weber.SceneGraphCore.GroupNode' does not implement interface member 'System.Collections.IEnumerable.GetEnumerator()'. 'Weber.SceneGraphCore.GroupNode.GetEnumerator()' cannot implement 'System.Collections.IEnumerable.GetEnumerator()' because it does not have the matching return type of 'System.Collections.IEnumerator'.

Answer 1

You can simply return children.GetEnumerator() in this case. (By the way your GroupNode object should implement IEnumerable and your GetEnumerator method should have the correct return type.)

public IEnumerator<ISceneNode> GetEnumerator()
{
    return children.GetEnumerator()
}

In more general cases though you can iterate over something and call yield return for each element.

Answer 2

Since IList already implements IEnumerable<>, you can just return children.GetEnumerator() in your GetEnumerator() method.