connection_factory.cs

public class ConnectionFactory : IConnectionFactory
{
	private static readonly IDictionary Strings = new Dictionary<string,string>();

	static ConnectionFactory()
	{
		lock(Strings.SyncRoot)
		{
			Strings.Add("key", "value");
		}
	}
	
	public SqlConnection GetConnection(string key)
	{
		//actually create connection
	}
}

public interface IConnectionFactory
{
	IDbConnection GetConnection(string key);
}