问题运行页面 [英] problem wher running page

问题描述

大家好，
我在dropdownlist数据绑定事件上写了以下代码
下拉列表的ID为"dupddatedist"

Hello all,
i have the following code thad i write on the dropdownlist databound event
the ID of dropdown list is"dupddatedist"

Protected Sub dupddatedist_DataBound(ByVal sender As Object, ByVal e As System.EventArgs) Handles ddupdatedist.DataBound
      Dim ddl As DropDownList = DirectCast(sender, DropDownList)
      'add an empty item on top of the list
      AddEmptyItem(ddl)
      Dim frmV As FormView = DirectCast(ddl.NamingContainer, FormView)
      'If frmV.DataItem IsNot Nothing Then

      'Let's pull the province value from the databound item.  The data
      'in my application is supplied by BLL as a dataview.  Therefore each
      'item bound to the FormView is of type DataRowView.  So let's cast
      'that DataItem to the appropriate type to be able to use it
      Dim intDistrict As Int32 = DirectCast(frmV.DataItem, DataRowView)("intContactPerson1DistrictID")
      ddl.ClearSelection()
      'be careful of the possibility that the value saved on the
      'database does not exist in the valid selections that are displayed
      'on the list
      Dim li As ListItem = ddl.Items.FindByValue(intDistrict)
      If li IsNot Nothing Then
          li.Selected = True
      End If

但是当我运行代码时，出现以下错误



从"DBNull"类型到"Integer"类型的转换无效.



请帮我知道我该怎么做
并为该问题编写正确的代码


谢谢和问候
Subiya ahsan

but when i run the code i got following error



Conversion from type ''DBNull'' to type ''Integer'' is not valid.



please help me out what shoul i do
and also write the correct code for the problem


Thanks and regards
Subiya ahsan

推荐答案

该探针最有可能在此行上:

Most likely the probelm is on this line:

Dim intDistrict As Int32 = DirectCast(frmV.DataItem, DataRowView)("intContactPerson1DistrictID")

在设置变量的值之前，请检查该变量是否不包含数据库中的null(在.Net中为DbNull.Value).有关示例，请参阅: http://msdn.microsoft.com/en-us/library/system.dbnull.aspx [ ^ ]

Before setting the value of the variable, check that it doesn''t contain a null from database, which would be a DbNull.Value in .Net. For an example, see: http://msdn.microsoft.com/en-us/library/system.dbnull.aspx[^]

这篇关于问题运行页面的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！