有关C#Windows App的帮助 [英] Help Regarding C# Windows App

问题描述

我正在制作一个考勤管理系统，它具有一个名为tblattendance的表，并且具有四个字段:

名称nvarchar(100)
timearrive nvarchar(100)允许为null
timeleave nvarchar(100)允许为null
登录代码nvarchar(100)

签入时，我从数据库中检查此人是否已签入，如果是，则他已签出，否则他已签入.

出现的问题是，当我在结帐时检查timeleave时，如果有人已经结帐(即timeleave！=")，然后显示一个消息框，则将其签出，则出现异常表"tblattendance"是DBNull."

I am making an attendance management system, it has a table named tblattendance and has four fields:

name nvarchar(100)
timearrive nvarchar(100) allow null
timeleave nvarchar(100) allow null
logincode nvarchar(100)

At time of check in, I check from database whether or not this person already checkedin,if yes he is checkedout else he checked in.

The problem arising is that when I check for timeleave at time of checkout that if person already checked out(i.e timeleave != "") then show a message box else check him out, exception is arising "The value for column "timeleave" in table "tblattendance" is DBNull."

if (a.GetAttendbyDt(uid, day)[0].TimeLeave !=  "")
                          {
                           //show message
                          }
else
//update attendance(check out)

GetAttendbyDT方法以用户名和当前日期为参数返回数据表.

谁能解决这个问题?

the GetAttendbyDT method returns a datatable by taking userid and current date as parameters.

Can any one solve this problem? How can I check for time leave null or not?

推荐答案

在其中键入Timelaeve！="的地方，而不是writeTimeleave！= NULL

Where you are typing Timelaeve != "", instead writeTimeleave != NULL

试试这个

if (a.GetAttendbyDt(uid, day)[0].TimeLeave.ToString().Trim() !=  "")

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