怎么用C#让sql中数据库的创建用户在服务器角色中sysadmin打上勾？

C# code

 public bool AddUser(string cUserName, string Password, string DB)        {            System.Data.SqlClient.SqlConnection oCon = new System.Data.SqlClient.SqlConnection                ("data source=.;initial catalog=master;password=334020;persist security info=True;user id=sa");            try            {                oCon.Open();            }            catch            {                return false;            }            System.Data.SqlClient.SqlCommand oAddUser = new System.Data.SqlClient.SqlCommand();            oAddUser.CommandType = System.Data.CommandType.Text;            oAddUser.Connection = oCon;            //oAddUser.CommandText="exec sp_addlogin '"+cUserName+"','"+Password+"','"+DB+"'";            oAddUser.CommandText = "CREATE LOGIN " + textBox1.Text + " WITH PASSWord='" + textBox2.Text + "', CHECK_POLICY=OFF ";            try            {                int i = oAddUser.ExecuteNonQuery();                if (i == 0)                {                    return false;                }                else                {                    MessageBox.Show("添加成功");                    return true;                }            }            catch            {                MessageBox.Show("添加失败,可能已经存在该用户名");                return false;            }        }