Hi @ibrahim1,
Is your ASP.NET Core application also running within the Docker host? If not, make sure that you have exposed the proper ports. Since you are running two nodes, you should also check out this thread: Could not bootstrap (NullReference when add Nodes) - Swarm - #10 by PierloCt - short story is that the Couchbase client needs access to each node. If you are trying to do this from outside the docker host, you will run into problems.