CODEWITHSUNDEEP
asp.netasp.net-4.0
GoldBishop
GoldBishop

Reputation: 2861

RadioButtonList SelectedIndexChanged generic event not firing

Developed a slightly dynamic page that builds a Question and Answer page based on information from a database. Everything works great except i cant get the RadioButtonList event to trigger with a minor MsgBox response to validate object sender and selected ListItem information.

Page_Load

    If Not Page.IsPostBack Then
        With Globals.tst

            .GetBrandInformation(Page.RouteData.Values("brand"),
              Page.RouteData.Values("year"),
              Page.RouteData.Values("month"))

            'Load up Question DataSet
            For Each quest As Question In .Questions

                Dim tr As New HtmlControls.HtmlTableRow
                Dim td As New HtmlControls.HtmlTableCell
                td.Attributes.Add("class", "tdQ")       'Add class attribute to <td> element, creating 'class="tdQ"'
                Dim lbl As New Label
                lbl.ID = "lbl" & quest.ID
                lbl.Text = quest.Text

                td.Controls.Add(lbl)
                tr.Cells.Add(td)
                tblContent.Rows.Add(tr)

                tr = New HtmlControls.HtmlTableRow
                td = New HtmlControls.HtmlTableCell
                td.Attributes.Add("class", "tdA")       'Add class attribute to <td> element, creating 'class="tdA"'

                Dim rbl As New RadioButtonList
                rbl.ID = "rblT" & .ID & "_Q" & quest.ID
                AddHandler rbl.SelectedIndexChanged, AddressOf rbl_SelectedIndexChanged     'Attach generic event handler to control

                Dim li As New ListItem

                'Load up Answer Dataset
                For Each answ As Answer In quest.Answers
                    li.Text = answ.Value
                    li.Value = "T" & .ID & "-Q" & quest.ID & "-A" & answ.ID & "-C" & answ.Correct

                    'Add built ListItem to RadioButtonList
                    rbl.Items.Add(li)
                    li = New ListItem
                Next

                td.Controls.Add(rbl)
                tr.Cells.Add(td)
                tblContent.Rows.Add(tr)
            Next

        End With
        '
    End If

Below is the Generic Event Handler Logic i am trying to attach to the RadioButtonList(s).

Protected Sub rbl_SelectedIndexChanged(sender As Object, e As EventArgs)
    MsgBox(CType(sender, RadioButtonList).ID & " Clicked.")
    MsgBox("Radio Button Selected: " & CType(sender, RadioButtonList).ID & " is Correct? " & CType(sender, RadioButtonList).SelectedValue)
End Sub

Anyone see anything wrong with the design, or know why the Event is not being triggered?

Edited 2012-11-20

Ok changed the rbl object to do AutoPostBack = true but that made life even more unbearable ;) Then quickly reverted back as the Q&A list i have is randomly generated on the Questions and Answers so the end-user would be given a new random order of questions upon every click of the ListItem.

Although i am getting some response back from the call backs still not getting the JavaScript response i am expecting by using either a defined JavaScript file or inline Response.Write/ClientScript.Register.

Created a debugging method into the Content Page:

Public Shared Sub Show(msg As String, Optional pg As Page = Nothing)
    Dim cmsg As String = msg.Replace("'", "\'")
    Dim scr As String = "<script type=""text/javascript"">alert('" & cmsg & "');</script>"

    If pg Is Nothing Then
        pg = CType(HttpContext.Current.CurrentHandler, Page)
    End If

    If (pg IsNot Nothing) And Not (pg.ClientScript.IsClientScriptBlockRegistered("alert")) Then
        pg.ClientScript.RegisterClientScriptBlock(GetType(Alert), "alert", scr)
    End If
End Sub

On page Load this method fires and as expected, but when placed inside the SelectedIndexChanged event it never fires off.

Still perplexed on why it works on general execution but not triggered execution.

Userful Method for those that like to create .Net methods that implement Javascript. .Net Slave - Javascript Alert.Show Class

Upvotes: 0

Views: 942

Answers (1)

Darren Wainwright
Darren Wainwright

Reputation: 30727

You have to take it OUT of the If Not Page.IsPostBack Then

this is because when you DO postback, the...

    AddHandler rbl.SelectedIndexChanged, AddressOf rbl_SelectedIndexChanged

...needs to be rebound before it can fire.

So basically, remove the If Not Page.IsPostBack Then and End If.

Oh, and get rid of the MsgBox() code too - this will kill the page from doing anything. If you want to output an Alert() then do something like:

    Dim script As String = String.Format("alert('{0}');", ""Radio Button Selected: " & CType(sender, RadioButtonList).ID & " is Correct? " & CType(sender, RadioButtonList).SelectedValue")
    page.ClientScript.RegisterClientScriptBlock(page.[GetType](), "alert", script, True)

UPDATE:

you also want to set AutoPostback = true; on your RBL. This tells the page to postback as soon as it's changed. the handler only fires if AutoPostBack is true.

Upvotes: 1

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