TransformBlock<TInput, TOutput>::ISourceBlock<TOutput>::ConsumeMessage Method (DataflowMessageHeader, ITargetBlock<TOutput>^, Boolean)

Called by a linked ITargetBlock<TInput> to accept and consume a DataflowMessageHeader previously offered by this ISourceBlock<TOutput>.

Namespace: System.Threading.Tasks.Dataflow
Assembly: System.Threading.Tasks.Dataflow (in System.Threading.Tasks.Dataflow.dll)

Syntax

C++

private:
virtual TOutput ConsumeMessage(
	DataflowMessageHeader messageHeader,
	ITargetBlock<TOutput>^ target,
	[OutAttribute] bool% messageConsumed
) sealed = ISourceBlock<TOutput>::ConsumeMessage

Parameters

messageHeader: Type: System.Threading.Tasks.Dataflow::DataflowMessageHeader
The DataflowMessageHeader of the message being consumed.

target: Type: System.Threading.Tasks.Dataflow::ITargetBlock<TOutput>^
The ITargetBlock<TInput> consuming the message.

messageConsumed: Type: System::Boolean
true if the message was successfully consumed; otherwise, false.

Return Value

Type: TOutput

The value of the consumed message. This may correspond to a different DataflowMessageHeader instance than was previously reserved and passed as the messageHeader to ConsumeMessage. The consuming ITargetBlock<TInput> must use the returned value instead of the value passed as messageValue through ITargetBlock<TInput>::OfferMessage.

If the message requested is not available, the return value will be null.

Implements

ISourceBlock<TOutput>::ConsumeMessage(DataflowMessageHeader, ITargetBlock<TOutput>^, Boolean)

Exceptions

Exception	Condition
ArgumentException	The messageHeader is not valid.
ArgumentNullException	The target is null.

Remarks

Only ITargetBlock<TInput> instances linked to this ISourceBlock<TOutput> instance may use ConsumeMessage, and it must only be used to consume DataflowMessageHeader instances previously offered by this source to the target.