Completing a TPL dataflow chain

Question

Given this code:

s_Batch = new BatchBlock<PerformanceRecord>(500);
s_Action = new ActionBlock<PerformanceRecord[]>(a => SendToDatabase(a));
s_Batch.LinkTo(s_Action);

When I'm done do I need to call Complete() on each block? Or will completing s_Batch trigger a complete in the blocks linked to it?

Answer 1

As your code stands now, you need to call Complete on all blocks individually:

s_Batch.Complete();
await s_Batch.Completion;

s_Action.Complete();
await s_Action.Completion;

You could however use DataflowLinkOptions while linking the blocks to request completion propagation:

s_Batch.LinkTo(s_Action, new DataflowLinkOptions {PropagateCompletion = true});
s_Batch.Complete();
await s_Batch.Completion;

This will propagate both completion and faulting notification to the linked target block (i.e. s_Action).

Answer 2

I like l3arnon's answer actually since it is the most concise.

This is something else I have done/seen with TPL blocks which also works.

s_Batch.Completion.ContinueWith( t => 
    { 
        if(t.IsFaulted) 
            ((IDataFlowBlock)s_Action).Fault(t.Exception);
        else
            s_Action.Complete();
    });
s_Batch.Complete();
s_Action.Completion.Wait();

Downside is that you will need to repeat this pattern for each linked block so you end up repeating yourself quite a bit.