FuncBlock

Overview

FuncBlock is a Dataflow block that receives data from a constantly-executing async method.

The async method for a FuncBlock is executed on the thread pool. If the method returns or throws OperationCanceledException, then the FuncBlock is completed. If the method throws some other exception, then the FuncBlock is faulted.

The first argument to the async method is a SendAsync delegate that looks like Task SendAsync(T item); that it can use to asynchronously send data to the FuncBlock. The optional second argument to the async method is a CancellationToken that is signaled when the async method should exit.

If the FuncBlock is requested to cancel (by signaling the CancellationToken member of its DataflowBlockOptions), then the block is canceled and then the async method is canceled by setting its CancellationToken and forcing SendAsync to throw OperationCanceledException.

If the FuncBlock is requested to complete (by calling Complete), then the block is completed and then the async method is canceled by setting its CancellationToken and forcing SendAsync to throw OperationCanceledException.

If the FuncBlock is requested to fault (by calling Fault), then the block is faulted and then the async method is canceled by setting its CancellationToken and forcing SendAsync to throw OperationCanceledException.

API

// A dataflow block which uses a function to generate its items.
public sealed class FuncBlock<T> : IReceivableSourceBlock<T>, IDisposable
{
  // Initializes the block with the specified options and a function which takes a cancellation token.
  public FuncBlock(Func<Func<T, Task>, CancellationToken, Task> function, DataflowBlockOptions dataflowBlockOptions = null);

  // Initializes the block with the specified options and a function which does not take a cancellation token.
  public FuncBlock(Func<Func<T, Task>, Task> function, DataflowBlockOptions dataflowBlockOptions = null);

  // Gets the name for this block.
  public string Name { get; }

  // Attempts to synchronously receive an available output item from the block.
  public bool TryReceive(Predicate<T> filter, out T item);

  // Attempts to synchronously receive all available items from the block.
  public bool TryReceiveAll(out IList<T> items);

  // Links the block to the specified ITargetBlock{TInput}.
  public IDisposable LinkTo(ITargetBlock<T> target, DataflowLinkOptions linkOptions);

  // Signals to the block that it should not produce any more messages.
  // This block will complete and then the next call to the function's "send" method will throw OperationCanceledException.
  public void Complete();

  // Gets a <see cref="Task"/> that represents the asynchronous operation and completion of the dataflow block.
  public Task Completion { get; }
}

Platform Support

This type is not supported on the following platforms:

• Windows Phone Silverlight 7.5.
• iOS.
• Android.
• Silverlight.