TPL DataFlow call a dataflow twice times

Question

I designed a complex dataflow consisting of various DataBlocks. I send a packet into the flow and receive a result on the end.

I work with

input.Post();
input.Complete();

// and later with
ReceiveAsync();

For the first call all works fine, but I don't know how to send the second data-packet through into the flow graph.

Inside the graph I also must use a WriteOnceBlock, can this be a problem for call the flow twice times?

Answer 1

You cannot use any of TPL Dataflow blocks after you've called the Complete method for them or for those who linked to them with completion propagation. So either you need to recreate your pipeline for each of your call, or (which is preferred) not to call Complete just for a one call.

Suggestions to your design:

• It seems that your're getting the data with Post/Receive methods in your pipeline, which can be substitute by linking the blocks. Moreover, you can use the completion propagation for this, so you'll remove all the continuation handlers in your code, if any.
• Are you sure that you needs the WriteOnceBlock? You can switch it to Broadcast, so you still has a value for a data, but it can be overridden by next call.
• If this is still not an option, you can unlink your WriteOnceBlock either by specifying the MaxMessages for linked blocks or by storing the IDisposable result of the LinkTo method so you can remove it for your next call, and create a new one WriteOnceBlock.