SqlCommand没有初始化？

Question

    //判断用户在数据库中是否存在
    public bool CheckUser()
    {
        //输入的用户名
        string userName = textName.Text.Trim();
        //输入的密码
        string userpwd = textPwd.Text.Trim();

        //确定查询用的SQL语句
        StringBuilder sb = new StringBuilder();

        //系统管理员登录
        if (this.comboType.Equals("管理员"))
        {
            sb.AppendFormat("SELECT COUNT(*) FROM Login WHERE name='{0}' AND pwd = '{1}'",userName,userpwd);
        }
        //执行查询
        //数据库查询的结果
        int count = 0;
        DBHelper db = new DBHelper();
        try
        {
            //打开连接
            db.OpenConnection();
            //创建Command命令
            SqlCommand comm = new SqlCommand(sb.ToString(), db.Connection);
            comm.CommandType = CommandType.Text;
             //ExecuteScalar:CommandText 属性尚未初始化!!!!!!!!!!!!!!!!!!!!!
            //执行查询语句
            count =(int)comm.ExecuteScalar();
            //如果结果大于0,验证通过,否则是非法用户
            if (count > 0)
            {
                return true;
            }
            else
            {
                return false;
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show(ex.Message,"系统提示");
            return false;
        }
        finally
        { 
        //关闭数据库连接
            db.CloseConnection();
        }
    }

            ![图片说明](https://img-ask.csdn.net/upload/201511/18/1447834844_126724.jpg)

Answer 1

说明if (this.comboType.Equals("管理员"))
{
sb.AppendFormat("SELECT COUNT(*) FROM Login WHERE name='{0}' AND pwd = '{1}'",userName,userpwd);
}这个没有执行，sb没有内容