如何访问循环中动态生成的复选框

Question

我是 asp.net 和 vb.net 编程的新手，我找不到我的问题的答案。我在运行时在一个循环中动态生成了一个复选框。

这是一个网格调度程序，它显示从不同页面选择的位置的选定日期和选定时间。我想通过 id 访问复选框，但我无法访问它们，因为复选框未在类级别声明。

谁能帮帮我，我整天都在寻找解决方案。我更喜欢 VB，但 C# 也很好。

下面是我的代码

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
    If Not IsPostBack Then
      BindLocationDayTime()
   End If
End Sub

Public Sub BindLocationDayTime()
        Dim ID As Integer
        Dim Name As String
        Dim Day As Integer
        Dim Time As Integer
        Dim StartDate As DateTime
        Dim EndDate As DateTime

        Dim Locations As SqlDataReader = GetLocations()

        For Each Item In Locations

            Dim LRow As New TableRow()
            Dim LCell As New TableCell()
            LCell.Text = Locations.Item("Name")
            LCell.Attributes.Add("class", "LocationHeader")
            LCell.Attributes.Add("colspan", "5")
            LRow.Cells.Add(LCell)
            LocationData.Rows.Add(LRow)

            Dim Location As SqlDataReader = GetLocation(Convert.ToInt32(Locations.Item("Id")))

            While Location.Read()
                Name = Location("Name").ToString()
                StartDate = Location("StartDate")
                EndDate = Location("EndDate")
            End While

            Dim dtfi As Globalization.DateTimeFormatInfo = Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat
            Dim tRowCount As Integer = 0

            Do While StartDate <= EndDate
                Dim LocationDayTime As SqlDataReader = GetPlayDayTime(Convert.ToInt32(Locations.Item("Id")))

                For Each row In LocationDayTime
                    Day = LocationDayTime.Item("DayID")
                    Time = LocationDayTime.Item("TimeID")
                    ID = Locations.Item("Id")
                    If Day = 1 Then
                        If StartDate.DayOfWeek = DayOfWeek.Monday Then
                            BindDays(StartDate, ID, tRowCount, Time)
                            tRowCount = tRowCount + 1
                        End If
                    ElseIf Day = 2 Then
                        If StartDate.DayOfWeek = DayOfWeek.Tuesday Then
                            BindDays(StartDate, ID, tRowCount, Time)
                            tRowCount = tRowCount + 1
                        End If
                    ElseIf Day = 3 Then
                        If StartDate.DayOfWeek = DayOfWeek.Wednesday Then
                            BindDays(StartDate, ID, tRowCount, Time)
                            tRowCount = tRowCount + 1
                        End If
                    ElseIf Day = 4 Then
                        If StartDate.DayOfWeek = DayOfWeek.Thursday Then
                            BindDays(StartDate, ID, tRowCount, Time)
                            tRowCount = tRowCount + 1
                        End If
                    ElseIf Day = 5 Then
                        If StartDate.DayOfWeek = DayOfWeek.Friday Then
                            BindDays(StartDate, ID, tRowCount, Time)
                            tRowCount = tRowCount + 1
                        End If
                    End If
                Next
                StartDate = StartDate.AddDays(1)
            Loop
        Next
    End Sub

Public Sub BindDays(ByVal StartDate As DateTime, ByVal ID As Integer, ByVal tRowCount As Integer, ByVal Time As Integer)
        Dim dtfi As Globalization.DateTimeFormatInfo = Threading.Thread.CurrentThread.CurrentCulture.DateTimeFormat
        Dim tRow As New TableRow()

        Dim Cell1 As New TableCell()
        Dim strDayOfWeek As String = dtfi.GetDayName(StartDate.DayOfWeek)
        Cell1.Text = UppercaseFirstLetter(strDayOfWeek & " ") & (StartDate.Date.ToShortDateString & " om ") & (Time & "uur ")
        Cell1.Attributes.Add("class", "MemberCell")
        tRow.Cells.Add(Cell1)

        Dim Cell2 As New TableCell()
        Dim cbAvailible As New CheckBox()
        cbAvailible.ID = (StartDate.Date) & "," & (Time)
        cbAvailible.Checked = False
        Cell2.Controls.Add(cbAvailible)
        tRow.Cells.Add(Cell2)

        Dim Cell3 As New TableCell()
        Dim Label As New Label()
        Label.Text = ("(Op deze datum ben ik verhinderd)")
        Cell3.Controls.Add(Label)
        tRow.Cells.Add(Cell3)

        If tRowCount Mod 2 Then
            tRow.Attributes.Add("class", "alternatingItemStyle")
        Else
            tRow.Attributes.Add("class", "itemStyle")
        End If

        LocationData.Rows.Add(tRow)

    End Sub

#End Region

#Region " Events "

Private Sub Insert_Click(sender As Object, e As EventArgs) Handles Insert.Click
' I want to get here al the checkbox id and insert the values to a databse
End Sub

End Region

Answer 1

解决方案 1 - 使用递归控制搜索

我已经对动态生成的表单进行了类似的操作，该表单具有可变数量的控件（文本框、下拉菜单和复选框），并且控件状态由数据驱动。我不希望与生成的控件的事件相关联（需要一个生涩的回发），但有一个“保存”按钮，并从该事件执行一个递归 GetChildControls 函数，该函数从包含动态控件的容器开始。在为每个动态控件分配 id 时有一个约定，这样当您稍后循环它们时，您可以知道哪个控件与哪个记录相关。

递归函数：

Public Class ControlUtils
    Shared Function GetChildControls(ByVal ctrl As Control, Optional ByVal ctrlType As Type = Nothing) As Control()
        Dim controls As New ArrayList()
        For Each c As Control In ctrl.Controls
            ' add this control and all its nested controls
            If ctrlType Is Nothing OrElse ctrlType.IsAssignableFrom(c.GetType()) Then
                controls.Add(c)
                controls.AddRange(GetChildControls(c))
            End If
        Next
        ' return the result as an array of Controls
        Return DirectCast(controls.ToArray(GetType(Control)), Control())
    End Function
End Class

具有人为动态形式的基本思想...

表示数据库信息的类：

Public Class Location
    Public Property ID As Integer
    Public Property Name As String
    Public Property StartDate As Date
    Public Property EndDate As Date

    Shared Function GetSampleLocations() As List(Of Location)
        Dim sample As New List(Of Location)
        Dim loc As Location
        For j = 1 To 5
            loc = New Location
            loc.ID = j
            loc.Name = "Location " & j
            loc.StartDate = Date.Today
            loc.EndDate = Date.Today.AddDays(6 - j)
            sample.Add(loc)
        Next
        Return sample
    End Function
End Class

具有构建“表单”并保存其数据的方法的类：

Public Class LocationsDynamicForm

    Dim _Locations As IEnumerable(Of Location)

    Sub New(locations As IEnumerable(Of Location))
        _Locations = locations
    End Sub

    Sub InsertEditForm(plc As PlaceHolder, setUserInput As Boolean)
        'build and add controls to placeholder
        Dim tbl As New Table
        Dim r As TableRow
        Dim c As TableCell
        For Each loc As Location In _Locations
            r = New TableRow

            'add cell for location name
            c = New TableCell
            c.Controls.Add(New LiteralControl(loc.Name)) 'add plain text through literal control
            r.Cells.Add(c)

            'add cell for each day in the date range for current location
            Dim currentDate As Date = loc.StartDate
            Do Until currentDate > loc.EndDate
                c = New TableCell
                Dim chk As New CheckBox
                chk.ID = "chkLocationDate_" & loc.ID & "_" & currentDate.Ticks
                chk.Text = currentDate.ToShortDateString
                If setUserInput Then
                    'set the check state based on current database value
                    Dim pretendValueCameFromDB As Boolean = True
                    chk.Checked = pretendValueCameFromDB
                End If
                c.Controls.Add(chk)
                r.Cells.Add(c)
                currentDate = currentDate.AddDays(1)
            Loop

            tbl.Rows.Add(r)
        Next
        plc.Controls.Add(tbl)
    End Sub

    Sub SaveForm(ByVal plc As PlaceHolder)
        Dim ctl As Control
        Dim controlIDParts() As String
        Dim drp As DropDownList
        Dim txt As TextBox
        Dim chk As CheckBox
        For Each ctl In ControlUtils.GetChildControls(plc, GetType(Control))
            If ctl.GetType Is GetType(DropDownList) Then
                drp = CType(ctl, DropDownList)
                If drp.ID Like "drpIT_*" Then
                    controlIDParts = drp.ID.Split("_")
                    'update record...
                End If
            ElseIf ctl.GetType Is GetType(TextBox) Then
                txt = CType(ctl, TextBox)
                If txt.ID Like "txtIT_*" Then
                    controlIDParts = txt.ID.Split("_")
                    'update record...
                End If
            ElseIf ctl.GetType Is GetType(CheckBox) Then
                chk = CType(ctl, CheckBox)
                If chk.ID Like "chkLocationDate_*" Then
                    controlIDParts = chk.ID.Split("_")
                    Dim locationID = controlIDParts(1)
                    Dim ticks As Long = Val(controlIDParts(2))
                    Dim d As New Date(ticks)
                    'update record...
                End If
            End If
        Next
        'commit record changes...
    End Sub

End Class

它在网络表单中的使用（假设你有一个保存按钮和占位符控件）：

Dim _Locations As List(Of Location)
Dim _LocationsForm As LocationsDynamicForm

Protected Sub Page_Init(sender As Object, e As EventArgs) Handles Me.Init
    _Locations = Location.GetSampleLocations()
    _LocationsForm = New LocationsDynamicForm(_Locations)
    _LocationsForm.InsertEditForm(plcLocations, Not Me.IsPostBack)
End Sub

Protected Sub btnSave_Click(sender As Object, e As EventArgs) Handles btnSave.Click
    _LocationsForm.SaveForm(plcLocations)
End Sub

解决方案 2 - 将 AddHandler 与动态添加的控件一起使用

这更接近您想要的，但需要在每个复选框更改时进行回发。添加复选框时，在 BindDays 例程中添加这些行。

cbAvailible.AutoPostBack = True
AddHandler cbAvailible.CheckedChanged, AddressOf Insert_Click

您应该修剪子 Insert_Click 签名末尾的 Handles 关键字。当您预先知道将要处理的控件但控件在设计时不存在时，Handles 非常好。

Private Sub Insert_Click(sender As Object, e As EventArgs)
    ' I want to get here al the checkbox id and insert the values to a databse
    Dim chk As CheckBox = CType(sender, CheckBox)
    Label1.Text = "ID = " & chk.ID & ", Checked = " & chk.Checked
End Sub

我不确定您是如何在回发中保留您的“LocationData”或将其添加到网页中，但我能够让您的代码的修改版本正常工作。

Answer 2

' Global declaration inside the "Form" class.
Public Checkboxes as New List(of Checkbox)

每次创建“新复选框”时，将其添加到集合中。

...
Dim cbAvailible As New CheckBox()
Checkboxes.Add(cbAvailable)
...

稍后您可以简单地通过索引引用复选框。

Dim chk as boolean = Checkboxes(2).checked ' example

另一种选择是使用 Generic.Dictionary 来存储复选框，在这种情况下，每个框都可以有一个“Key”，例如与行或特定内容相关的字符串。

循环通过复选框。

For iQ AS integer = 0 to Checkboxes.Count -1
    Dim cb as checkbox = Checkboxes(iq) ' just a way to not use long name during operations.
    Dim checked as boolean = cb.checked ' ... ' do your work here
    ' ...
Next iQ

您可能需要对所有对象（每行）执行相同操作。

最后一个索引对于所有这些都应该相同。这也应该与表格对象中的行数相同。