Parallel iteration in C#?

Question

Is there a way to do foreach style iteration over parallel enumerables in C#? For subscriptable lists, I know one could use a regular for loop iterating an int over the index range, but I really prefer foreach to for for a number of reasons.

Bonus points if it works in C# 2.0

Answer 1

.NET 4's BlockingCollection makes this pretty easy. Create a BlockingCollection, return its .GetConsumingEnumerable() in the enumerable method. Then the foreach simply adds to the blocking collection.

E.g.

private BlockingCollection<T> m_data = new BlockingCollection<T>();

public IEnumerable<T> GetData( IEnumerable<IEnumerable<T>> sources )
{
    Task.Factory.StartNew( () => ParallelGetData( sources ) );
    return m_data.GetConsumingEnumerable();
}

private void ParallelGetData( IEnumerable<IEnumerable<T>> sources )
{
    foreach( var source in sources )
    {
        foreach( var item in source )
        {
            m_data.Add( item );
        };
    }

    //Adding complete, the enumeration can stop now
    m_data.CompleteAdding();
}

Hope this helps. BTW I posted a blog about this last night

Andre