shows how the foreach does not necessarily require an IEnumerable. Demonstrates the use of Duck typing in C#

duckable.cs

// resembles a IEnumerator. has Current and MoveNext
public class Duckerator
{
    public bool MoveNext()
    {
        return false;
    }

    public Object Current { get; private set; }
}

//represents an IEnumerable. has a GetEnumerator method
public class Duckable
{
    public Duck GetEnumerator()
    {
        return new Duckerator();
    }
}

public void TestADuck()
{
    var duckable = new Duckable();
    foreach(var duckItem in duckable)
    {
          //no compile errors...
    }
}