如何从 vb.net 的列表框中获取选定的项目
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How to get selected items from listbox from vb.net
提问by bhu
I'm using ListBoxto display some value, it works properly but when I am trying to get the selected item from the list box it shows an error null reference error.
我ListBox用来显示一些值，它工作正常，但是当我尝试从列表框中获取所选项目时，它显示错误空引用错误。
Below is my code that I have written to get values from ListBox:
下面是我为从 ListBox 获取值而编写的代码：
For i As Integer = 0 To lsttasks.SelectedItems.Count - 1
userTaskDtlSrNo = Val(lsttasks.SelectedItems(i).ToString())
If userTaskDtlSrNos <> "" Then userTaskDtlSrNos &= ","
userTaskDtlSrNos &= userTaskDtlSrNo
Next
Can anyone tell me what's wrong with this code?
谁能告诉我这段代码有什么问题？
回答by Leon
You don't need the Val()function there
你不需要Val()那里的功能
Don't forget to declare Dim userTaskDtlSrNo as String
别忘了申报 Dim userTaskDtlSrNo as String
Use: userTaskDtlSrNo = lsttasks.SelectedItems(i).ToString()
用： userTaskDtlSrNo = lsttasks.SelectedItems(i).ToString()
回答by 0000
I believe your assigning a string to a integer, declare userTaskDtlSrNo as String, then use
我相信您将字符串分配给整数，将 userTaskDtlSrNo 声明为字符串，然后使用
userTaskDtlSrNo = Val(lsttasks.SelectedItems(i).ToString())
if you need to change userTaskDtlSNo to an integer after then just use
如果您需要在之后将 userTaskDtlSNo 更改为整数，则只需使用
Dim intUserTask As Integer
Integer.TryParse(userTaskDtlSrNo, intUserTask)
to assign a new variable with same value as an integer, i dont know the rest of your code but i see no reason why this would not solve your problem. :-)
分配一个与整数相同值的新变量，我不知道你的其余代码，但我看不出为什么这不能解决你的问题。:-)
回答by Agentleader1
This can be way easier than it looks.
这可能比看起来容易得多。
If you want to delete an object that is selected:
如果要删除选定的对象：
'let recips be the listbox name
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
Recips.Items.Remove(Recips.SelectedItem)
End Sub
If you want to get the selected item (like for setting it to a string):
如果要获取所选项目（例如将其设置为字符串）：
'let pie be a string variable, and recips to be the listbox again respectively
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
pie = Recips.selectedItem
End Sub
I hope this was enough for you, I'm not sure if I covered on enough information. Please comment so, if I forgot. Accept this answer if this helped.
我希望这对你来说已经足够了，我不确定我是否涵盖了足够的信息。请评论，如果我忘记了。如果这有帮助，请接受此答案。
