代码plz中的错误检查并解释代码 [英] error in code plz check and plz explain the code

问题描述

表名用户

tablename User

bn            int
Email         varchar(500)
Password      varchar(500)
Name          varchar(500)
Country       varchar(500)
LastLogin     datetime
RegisterDate  datetime
Description   Varchar(500)
ImageName     Varchar(500)

 if (!Page.IsPostBack)
        {
            GetUserDetails(int.Parse(Request.QueryString["bn"].ToString()));// object reference not set to an instance of an object

        }
}
 public void GetUserDetails(int mu)
    {
        string getUserDetail = "Select bn,Email,Name,Country,Convert(varchar (20), RegisterDate, 106) RegisterDate,Convert(varchar (20), LastLogin, 106) LastLogin ,Description,ImageName FROM [User] where bn=''" + mu+ "''";
        dt = dbClass.ConnectDataBaseReturnDT(getUserDetail);
        if (dt.Rows.Count > 0)
        {
            UserImage.ImageUrl = "~/UserImage/" + dt.Rows[0]["ImageName"].ToString();
            lblCreated.Text = dt.Rows[0]["RegisterDate"].ToString();
            LabelLastLogin.Text = dt.Rows[0]["LastLogin"].ToString();
            lblCreated.Text = dt.Rows[0]["RegisterDate"].ToString();
            LabelAboutMe.Text = dt.Rows[0]["Description"].ToString();
        }
    }

[edit]已添加代码块，忽略HTML ..."选项已禁用-OriginalGriff [/edit]

[edit]Code block added, "Ignore HTML..." option disabled - OriginalGriff[/edit]

推荐答案

GetUserDetails(int.Parse(Request.QueryString["bn"].ToString()));// object reference not set to an instance of an object

提示在错误消息中:
那里的东西评估为空.
由于ToString始终返回某种形式的字符串，因此必须是"bn"不在QueryString列表中...

The clue is in the error message:
Something there evaluates to null.
Since ToString always returns a string of some form, it must be that "bn" is not in the QueryString list...

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