yield and Dispose()

Consider this code:

Code:

---

    class Test : IDisposable
    {
        public void Dispose()
        {
            Console.WriteLine("dispose");
        }
    }

    static IEnumerable<int> Bla()
        {
            using (new Test())
            {
            }
            yield return 1;
            yield return 2;
            yield return 3;
        }

---

I would expect after the using statement that dispose of Test is called when calling Bla(). But it isn't
Dispose is only called when calling Bla in a loop.

Code:

---

foreach (int i in Bla()) {break;}

---

Why?

That's because before you actually materialize your enumerable, Blah() isn't even called. Put a writeline before the new and you will see.

Code:

---

IEnumerable<int> GetAllData()
{
yield 1;
yield 2;
yield 3;
}

var data = GetAllData(); // <- function is NOT called. You got an IEnumerable. Not the actual data, but rather a hint where to get data, should it really be enumerated.

var materialized_data = data.ToList(); // <- now it gets called, the list will materialize the data

---

I see, thanks