SQL Server 2005 Connectivity problem from .NET

I'm unable to connect to SQL Server 2005 from .NET. I'm getting the error " A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) ". The strange thing is, I'm able to connect through management studio using the same credentials (SQL Server authenticatio开发者_StackOverflown).

My connection string is: Server=servername;User ID=xxx;Password=xxx

I'm using the 2005 native client.

Also, I just realized Management Studio cannot connect if using named pipes, only TCP/IP.

What tells ADO.NET which protocol to use?

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SQL Server 2005 may not be allowing inbound named pipes connections. This can be configured differently for the older SQL Server protocol and for the 2005+ Native Client. Check the SQL Server Configuration Manager on your database server.

(And yes, the Management Studio would still be able to connect to the remote database if named pipes were disallowed.)