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");