ISourceBlock<TOutput>.ConsumeMessage Method

Definition

Namespace:

System.Threading.Tasks.Dataflow

Assembly:

System.Threading.Tasks.Dataflow.dll

Package:

System.Threading.Tasks.Dataflow v9.0.0-rc.2.24473.5

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

public TOutput? ConsumeMessage (System.Threading.Tasks.Dataflow.DataflowMessageHeader messageHeader, System.Threading.Tasks.Dataflow.ITargetBlock<out TOutput> target, out bool messageConsumed);

abstract member ConsumeMessage : System.Threading.Tasks.Dataflow.DataflowMessageHeader * System.Threading.Tasks.Dataflow.ITargetBlock<'Output> * bool -> 'Output

Public Function ConsumeMessage (messageHeader As DataflowMessageHeader, target As ITargetBlock(Of Out TOutput), ByRef messageConsumed As Boolean) As TOutput

Parameters

messageHeader

DataflowMessageHeader

The DataflowMessageHeader of the message being consumed.

target

ITargetBlock<TOutput>

The ITargetBlock<TInput> consuming the message.

messageConsumed

Boolean

true if the message was successfully consumed; otherwise, false.

Returns

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(DataflowMessageHeader, ITargetBlock<TOutput>, Boolean). The consuming ITargetBlock<TInput> must use the returned value instead of the value passed as messageValue through OfferMessage(DataflowMessageHeader, TInput, ISourceBlock<TInput>, Boolean).

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

Exceptions

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.