How to drop a data

Question

Hello.

I have 3 blocks:
TransoftmBlock b1,b2;
ActionBlock b3;

b1.LinkTo(b2); b2.LinkTo(b3);

In some cases I want to drop operation:

b1 gets error during operation, and I want to correctly drop this message, but I cant found how to do it: I need to pass null and b2 and b3 needs to correctly handles this invalid messages.

I really need way to drop operation in some cases, but how to do it?

Thanks!

Answer 1

I can see two options here:

1. Use the overload of LinkTo() that takes a predicate. Something like

   b1.LinkTo(b2, x => x != null);

2. Use TransformManyBlock instead of your TransformBlock and produce a sequence containing only the single result on success and an empty sequence on failure.

Answer 2

Both of your approaches are reasonable.  For #1, you can subsequently link b1 to DataflowBlock.NullTarget, such that any data that isn't consumed by b2 will be dropped.