How to yield a nested IENumerable?

Question

I know how to yield values in a method with return value IENumerable

public IEnumerable<int> GetDigits()
{
    yield return 1;
    yield return 1;
    yield return 1;
}

but how is the correct Syntax for a nested IEnumerable<IEnumerable<int>>?

public IEnumerable<IEnumerable<int>> GetNestedDigits()
{
    yield return yield return 1; //??
}

Answer 1

You cannot directly nest the yield return statements. You'd have to create another method:

public IEnumerable<IEnumerable<int>> GetNestedDigits()
{
    yield return GetNestedEnumerable();
}

public IEnumerable<int> GetNestedEnumerable()
{
    yield return 1;
}