Question

There is some code that I’m trying to convert from IList to IEnumerable:

[Something(123)]
public IEnumerable<Foo> GetAllFoos()
{
  SetupSomething();

  DataReader dr = RunSomething();
  while (dr.Read())
  {
    yield return Factory.Create(dr);
  }
}

The problem is, SetupSomething() comes from the base class and uses:

Attribute.GetCustomAttribute(
    new StackTrace().GetFrame(1).GetMethod(), typeof(Something))

yield ends up creating MoveNext(), MoveNext() calls SetupSomething(), and MoveNext() does not have the [Something(123)] attribute.

I can’t change the base class, so it appears I am forced to stay with IList or implement IEnumerable manually (and add the attribute to MoveNext()).

Is there any other way to make yield work in this scenario?

Answer 1

You can wrap the method in another method that does all required preprocessing:

[Something(123)]
public IEnumerable<Foo> GetAllFoos()
{
    SetupSomething();
    return GetAllFoosInternal();
}

private IEnumerable<Foo> GetAllFoosInternal()
{
    DataReader dr = RunSomething();
    while (dr.Read())
    {
        yield return Factory.Create(dr);
    }
}