.NET Framework Parallel Dataflow, Part 3: Listing 1

UiUpdateBlock.cs

using System;
using System.Threading.Tasks;
using System.Threading.Tasks.Dataflow;
using Windows.UI.Xaml.Controls;

namespace VSMDataflowPart3
{
    public class UiUpdateBlock<T> : IPropagatorBlock<T, T>
    {
        private readonly ITargetBlock<T> _target;
        private readonly ISourceBlock<T> _source;

        public UiUpdateBlock(TextBlock element)
        {
            _target = new ActionBlock<T>(x => element.Text = x.ToString(),
                new ExecutionDataflowBlockOptions() 
                { TaskScheduler = TaskScheduler.FromCurrentSynchronizationContext() });
            _source = new BroadcastBlock<T>(x => x);
        }

        public DataflowMessageStatus OfferMessage(DataflowMessageHeader messageHeader,
            T messageValue, ISourceBlock<T> source, bool consumeToAccept)
        {
            return _target.OfferMessage(messageHeader, messageValue,
                source, consumeToAccept);
        }

        public void Complete()
        {
            _target.Complete();
        }

        public Task Completion
        {
            get { return _source.Completion; }
        }

        public void Fault(Exception exception)
        {
            _target.Fault(exception);
        }

        public T ConsumeMessage(DataflowMessageHeader messageHeader,
            ITargetBlock<T> target, out bool messageConsumed)
        {
            return _source.ConsumeMessage(messageHeader,
                target, out messageConsumed);
        }

        public IDisposable LinkTo(ITargetBlock<T> target, DataflowLinkOptions linkOptions)
        {
            return _source.LinkTo(target, linkOptions);
        }

        public void ReleaseReservation(DataflowMessageHeader messageHeader, ITargetBlock<T> target)
        {
            _source.ReleaseReservation(messageHeader, target);
        }

        public bool ReserveMessage(DataflowMessageHeader messageHeader, ITargetBlock<T> target)
        {
            return _source.ReserveMessage(messageHeader, target);
        }
    }
}

About the Author

Eric Vogel is a Senior Software Developer for Red Cedar Solutions Group in Okemos, Michigan. He is the president of the Greater Lansing User Group for .NET. Eric enjoys learning about software architecture and craftsmanship, and is always looking for ways to create more robust and testable applications. Contact him at vogelvision@gmail.com.