ActionBlock<TInput>.Completion Property
Definition
Important
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Gets a Task object that represents the asynchronous operation and completion of the dataflow block.
public:
property System::Threading::Tasks::Task ^ Completion { System::Threading::Tasks::Task ^ get(); };public System.Threading.Tasks.Task Completion { get; }member this.Completion : System.Threading.Tasks.TaskPublic ReadOnly Property Completion As TaskProperty Value
The completed task.
Implements
Examples
The following example shows how to use the Completion property to wait for all messages to propagate through the network. This code example is part of a larger example provided for the How to: Specify the Degree of Parallelism in a Dataflow Block topic.
// Performs several computations by using dataflow and returns the elapsed
// time required to perform the computations.
static TimeSpan TimeDataflowComputations(int maxDegreeOfParallelism,
int messageCount)
{
// Create an ActionBlock<int> that performs some work.
var workerBlock = new ActionBlock<int>(
// Simulate work by suspending the current thread.
millisecondsTimeout => Thread.Sleep(millisecondsTimeout),
// Specify a maximum degree of parallelism.
new ExecutionDataflowBlockOptions
{
MaxDegreeOfParallelism = maxDegreeOfParallelism
});
// Compute the time that it takes for several messages to
// flow through the dataflow block.
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
for (int i = 0; i < messageCount; i++)
{
workerBlock.Post(1000);
}
workerBlock.Complete();
// Wait for all messages to propagate through the network.
workerBlock.Completion.Wait();
// Stop the timer and return the elapsed number of milliseconds.
stopwatch.Stop();
return stopwatch.Elapsed;
}
' Demonstrates how to specify the maximum degree of parallelism
' when using dataflow.
Friend Class Program
' Performs several computations by using dataflow and returns the elapsed
' time required to perform the computations.
Private Shared Function TimeDataflowComputations(ByVal maxDegreeOfParallelism As Integer, ByVal messageCount As Integer) As TimeSpan
' Create an ActionBlock<int> that performs some work.
Dim workerBlock = New ActionBlock(Of Integer)(Function(millisecondsTimeout) Pause(millisecondsTimeout), New ExecutionDataflowBlockOptions() With { .MaxDegreeOfParallelism = maxDegreeOfParallelism})
' Simulate work by suspending the current thread.
' Specify a maximum degree of parallelism.
' Compute the time that it takes for several messages to
' flow through the dataflow block.
Dim stopwatch As New Stopwatch()
stopwatch.Start()
For i As Integer = 0 To messageCount - 1
workerBlock.Post(1000)
Next i
workerBlock.Complete()
' Wait for all messages to propagate through the network.
workerBlock.Completion.Wait()
' Stop the timer and return the elapsed number of milliseconds.
stopwatch.Stop()
Return stopwatch.Elapsed
End Function
Private Shared Function Pause(ByVal obj As Object)
Thread.Sleep(obj)
Return Nothing
End Function
Remarks
A dataflow block is considered completed when it is not currently processing a message and when it has guaranteed that it will not process any more messages. The returned Task will transition to a completed state when the associated block has completed. It will transition to the RanToCompletion state when the block completes its processing successfully according to the dataflow block's defined semantics. It will transition to the Faulted state when the dataflow block has completed processing prematurely due to an unhandled exception, and it will transition to the Canceled state when the dataflow block has completed processing prematurely after receiving a cancellation request. If the task completes in the Faulted state, its Exception property returns an AggregateException exception that contains one or more exceptions that caused the block to fail.
