How do I implement Parallel.For correctly in getting correct state?

Question

I have a list of ports that I go through sequentially in order to connect to a database. Normally, there's a default port that works, but there are connections that use a non-standard port (which I don't have any visibility). There are about 20-30 of them, and going through them sequentially would take a long time.

Below, I made my first attempt in parallelizing the sequential algorithm in connecting to the ports.

nonStdPorts = {...}; // list of all non-standard ports (max: 30); 


ConnectionState state = ConnectionState.FAIL; 
ConcurrentStack<ConnectInfo> results = new ConCurrentStack<ConnetInfo>(); 

// Assume single instance. Add an outer for-loop if multiple instances are present. 
Parallel.For(0, nonStdPorts.Length, (i, loopState) =>
    {
        ConnectInfo connector = new ConnectInfo(serverName, databaseName, port); 
        connector.State = TryConnect(serverName, databaseName, nonStdPorts[i], ref   dbConnection);  
        results.Push(connector); 

        if (connector.State == ConnectionState.SUCCESSFUL) 
        {
            loopState.Stop(); 
        }
    }
); 

The helper class, ConnectInfo, is defined below:

class ConnectInfo 
{
   ConnectInfo(serverName, databaseName, port) {} 
   State { get; set; } 
   DbConnection { get; set; } 
}

and the ConnectionState being an enum holding only: FAIL or SUCCESSFUL. (I'm only interested in getting the SUCCESSFUL state).

My thinking is that if it's successful to get a connection to 1 port, it would bail out with the information (server, database, which port and the connection) on first chance.

Am I doing this correctly (especially getting out of the Parallel.For loop)?

Answer 1

For a parallel solution, ref dbConnection looks very conspicuous.

You probably don't need the ref and a Database connection can usually not be shared among threads.