queue.IsCompleted returns false even when the queue is empty?

Question

The following code never return. Debugging shows that the queue.IsCompleted returns false even when the queue is empty. Did I miss anything?

var workers = new Task[1];
using (var queue = new BlockingCollection<QueuePayload>(20))
{
    workers[0] = Task.Run(() => Consume(queue));
    queue.Add(new QueuePayload{....});
    Task.WaitAll(workers);
}

void Consume(BlockingCollection<QueuePayload> queue))
{
    while (!queue.IsCompleted)
    {
        var i = new QueuePayload();
        try
        {
            i = queue.Take();
        }
        catch (InvalidOperationException)
        {
            break;
        }
    ......

Answer 1

The property for IsCompleted at https://msdn.microsoft.com/en-us/library/dd267315(v=vs.110).aspx has the following text:

Whether this collection has been marked as complete for adding and is empty.

Where do you mark the collection as completed? This is not an empty check - it is an empty check with a manual additional switch.

There is accordingly a CompleteAdding() method that marks that no more items will be added.