subscribe-filter-replace

Importing the AMPS client library:

using AMPS.Client;
using AMPS.Client.Exceptions;

Constructing the command:

Command cmd = new Command(Message.Commands.Subscribe)
                  .setTopic(topic)
                  .setSubId(existingSubId)
                  .setFilter(filter)
                  .setOptions(Message.Options.Replace
                              // + other options to match existing subscription
                             )
              ;

The command can now be used in execute or executeAsync.