javascript - 取消选中后面代码中 CheckedChanged 上的最后一个复选框

Question

我有一个 gridview，其中有一个 itemtemplate 列，其中有一个复选框。我只希望用户选择其中 3 个复选框。在第四次选择时，我想弹出一条消息，告诉他们只允许 3 个，然后取消选中他们刚刚选中的复选框。我尝试了不同的 JavaScript，但无法让它工作。

现在我非常接近在 CheckedChanged 事件后面的 vb 代码中完成此操作。我可以在第四个选择时弹出消息，但无法取消选中该框。我以为 box.Checked = False 可以做到这一点，但事实并非如此。我需要对发件人做些什么吗？或者我是否接近我所拥有的？

Protected Sub CheckBoxPain_CheckedChanged(sender As Object, e As System.EventArgs)

    Dim box As CheckBox
    Dim numChecked As Integer = 0

    For Each row As GridViewRow In gv_pain.Rows
        If row.RowType = DataControlRowType.DataRow Then
            box = CType(row.Cells(0).FindControl("CheckBoxPain"), CheckBox)
            If box.Checked Then
                numChecked = numChecked + 1
            End If
        End If
    Next

    'Response.Write("NUM:" & numChecked.ToString)
    'Response.Write("STATUS:" & box.Checked.ToString)
    'Response.Write("ITEM:" & box.SelectedItem.Text)

    If numChecked.ToString > 3 Then
        Response.Write("<script>alert('Only 3 Pain Selections allowed')</script>")
        box.Checked = False
    End If

End Sub

Answer 1

我通过添加 UnCheckMe 变量并获取 CType(sender, Checkbox) 解决了这个问题，如下所示:

Protected Sub CheckBoxPain_CheckedChanged(sender As Object, e As System.EventArgs)

    Dim box As CheckBox
    Dim numChecked As Integer = 0
    Dim GridCategory As String = "Pain"

    For Each row As GridViewRow In gv_pain.Rows
        If row.RowType = DataControlRowType.DataRow Then
            box = CType(row.Cells(0).FindControl("CheckBox" & GridCategory), CheckBox)
            If box.Checked Then
                numChecked = numChecked + 1
            End If
        End If
    Next

    Dim MaxChecked As String = "3"
    If numChecked.ToString > MaxChecked Then
        Response.Write("<script>alert('Only " & MaxChecked & " " & GridCategory & " Selections allowed, uncheck one to make a new selection.')</script>")

        Dim UnCheckMe = CType(sender, CheckBox)
        UnCheckMe.Checked = False
    End If

End Sub