ado.net(1)

SqlConnection theConnection = new SqlConnection();
            //创建一个connection的对象实例
            theConnection.ConnectionString = "server=.;integrated security=true;";
            //设置其连接字符串，本地连接，集成安全连接
            //在连接字符串作为参数传给创建connection对象实例的代码前，最好将其赋给一个字符串
            //string connectionstring = "server=.;integrated security=true;";
            //SqlConnection theconnection=new SqlConnection(connectionstring);
            //在连接字符串作为参数传给创建connection"
            theConnection.Open();
            if (theConnection.State == System.Data.ConnectionState.Open)
                Console.WriteLine("database connection is open");