I've created a Dataflow pipeline consisting of 4 blocks (which includes one optional block) which is responsible for receiving a query object from my application across HTTP and retrieving information from a database, doing an optional transform on that data, and then writing the information back in the HTTP response.

In some testing I've done I've been pulling down a significant amount of data from the database (570 thousand rows) which are stored in a List object and passed between the different blocks and it seems like even after the final block has been completed the memory isn't being released. Ram usage in Task Manager will spike up to over 2 GB and I can observe several large spikes as the List hits each block.

The signatures for my blocks look like this:

private TransformBlock<HttpListenerContext, Tuple<HttpListenerContext, QueryObject>> m_ParseHttpRequest;
private TransformBlock<Tuple<HttpListenerContext, QueryObject>, Tuple<HttpListenerContext, QueryObject, List<string>>> m_RetrieveDatabaseResults;
private TransformBlock<Tuple<HttpListenerContext, QueryObject, List<string>>, Tuple<HttpListenerContext, QueryObject, List<string>>> m_ConvertResults;
private ActionBlock<Tuple<HttpListenerContext, QueryObject, List<string>>> m_ReturnHttpResponse;

They are linked as follows:

m_ParseHttpRequest.LinkTo(m_RetrieveDatabaseResults);
m_RetrieveDatabaseResults.LinkTo(m_ConvertResults, tuple => tuple.Item2 is QueryObjectA);   
m_RetrieveDatabaseResults.LinkTo(m_ReturnHttpResponse, tuple => tuple.Item2 is QueryObjectB);           
m_ConvertResults.LinkTo(m_ReturnHttpResponse);

Is it possible that I can set up the pipeline such that once each block is done with the list they no longer need to hold on to it as well as once the entire pipeline is completed that the memory is released?