Using yield to iterate over a datareader might not close the connection?

Question

Here is a sample code to retrieve data from a database using the yield keyword that I found in a few place while googling around :

public IEnumerable

        

Answer 1

From the simple test I have tried, aku is right, dispose is called as soon as the foreach block exit.

@David : However call stack is kept between call, so the connection would not be closed because on the next call we would return to the next instruction after the yield, which is the while block.

My understanding is that when the iterator is disposed, the connection would also be disposed with it. I also think that the Connection.Close would not be needed because it would be taken care of when the object is disposed because of the using clause.

Here is a simple program I tried to test the behavior...

class Program
{
    static void Main(string[] args)
    {
        foreach (int v in getValues())
        {
            Console.WriteLine(v);
        }
        Console.ReadKey();

        foreach (int v in getValues())
        {
            Console.WriteLine(v);
            break;
        }
        Console.ReadKey();
    }

    public static IEnumerable getValues()
    {
        using (TestDisposable t = new TestDisposable())
        {
            for(int i = 0; i<10; i++)
                yield return t.GetValue();
        }
    }
}

public class TestDisposable : IDisposable
{
    private int value;

    public void Dispose()
    {
        Console.WriteLine("Disposed");
    }

    public int GetValue()
    {
        value += 1;
        return value;
    }
}