[c#] When using Trusted_Connection=true and SQL Server authentication, will this affect performance?

If a connection string specifies Trusted_Connection=true with SQL Server authentication mode, will performance of my web application be impacted?

This will probably have some performance costs when creating the connection but as connections are pooled, they are created only once and then reused, so it won't make any difference to your application. But as always: measure it.

UPDATE:

There are two authentication modes:

1. Windows Authentication mode (corresponding to a trusted connection). Clients need to be members of a domain.
2. SQL Server Authentication mode. Clients are sending username/password at each connection

If your web application is configured to impersonate a client, then using a trusted connection will potentially have a negative performance impact. This is because each client must use a different connection pool (with the client's credentials).

Most web applications don't use impersonation / delegation, and hence don't have this problem.

See this MSDN article for more information.

When you use trusted connections, username and password are IGNORED, because SQL Server using windows authentication.