Dynamically loading ascx page and having events fire

Discussion in 'ASP .Net Building Controls' started by Shawn Meyer, Jan 31, 2004.

  1. Shawn Meyer

    Shawn Meyer Guest

    Im sure this has been discussed here before but I have had no luck finding
    an answer.

    I am trying to create a simple web app, with a navigation on one side that
    will load up pages on the other. The nav side is a custom control, that has
    an event that fires upon click, and then sets a selectedindex. I am using
    the selected index to determine what ascx page to load up. I created a
    "LoadControl" function to load the ascx page and add it to the placeholder
    controls. This function gets called when the selectedindexchaged event
    fires (which is mapped to the nav control), and a viewstate variable gets
    set. The PostBack function checks for this variable and if there, calls the
    loadcontrol again.

    ** The ascx pages that I load have post back items on them, such as a
    textboxs and submit button.
    The nav events fire, which loads the ascx correctly, however the first time
    I hit submit button, the button click event (on the loaded ascx page) does
    not fire. Every time after that the event fires properly.

    From what I have read, when you load an ascx after the after the pageload
    has executed (ie. due to a event ) your events on the loaded page will not
    work properly because they were not loaded during pageload. And after the
    second click it worked because of my call to LoadControl in the postback.

    Some people have suggested to load all of your pages, and toggle visibility,
    but this really isn't an option since I plan on having a large number of
    pages on the site.

    Is there any way to make this work? Attached is the code snips.


    -- Page load
    <snip>
    if ( isPostBack )

    {

    if (ViewState["Control1"] != null )

    {

    LoadControl();

    }

    }

    <snip>

    private System.Web.UI.Control home_control;

    private void LoadControl()

    {

    switch (FooterPanelBar.SelectedIndex)

    {

    case 0:


    home_control = LoadControl("a.ascx");

    PlaceHolder_Body.Controls.Add(home_control);

    break;

    case 1:

    home_control = LoadControl("b.ascx");

    PlaceHolder_Body.Controls.Add(home_control);


    break;

    }

    }



    private void FooterPanelBar_SelectedIndexChanged(object sender, EventArgs e)

    {

    PlaceHolder_Body.Controls.Clear(); // clear out the loaded one to
    perform switch to new ascx

    LoadControl();


    ViewState["Control1"] = "Control1";

    }

    Thanks, Shawn Meyer
     
    Shawn Meyer, Jan 31, 2004
    #1
    1. Advertisements

  2. hi Shawn,
    You need to supply an id to your control. This is because the second time
    you load the control you are loading it in a different location.
    In your LoadControl method, right after you add your control to the
    placeholder supply an id and the problem is solved, like :

    switch (FooterPanelBar.SelectedIndex)

    {

    case 0:


    home_control = LoadControl("a.ascx");

    PlaceHolder_Body.Controls.Add(home_control);
    home_control.id = "a";

    break;

    case 1:

    home_control = LoadControl("b.ascx");

    PlaceHolder_Body.Controls.Add(home_control);
    home_control.id = "b";

    break;

    }

    doesswitch (FooterPanelBar.SelectedIndex)
     
    Alessandro Zifiglio, Jan 31, 2004
    #2
    1. Advertisements

  3. if its not clear what i mean by a different location, i mean one time you
    add it when the selected index changes, and another time you add it in
    page_load --supplying an id is the way to resolve.
     
    Alessandro Zifiglio, Jan 31, 2004
    #3
  4. Shawn Meyer

    Shawn Meyer Guest

    This didnt work. The events on the loaded ascx will not fire, on the first
    postback. After the first postback everything works as planned. Any
    thoughts?



     
    Shawn Meyer, Feb 2, 2004
    #4
  5. This works perfectly. I had reconstructed your exact same scenario before
    posting. With the only difference that i were using a radiobuttonlist
    control and loading controls in its selectedIndex changed event.
    Also note that initially when not supplying an explicit id I experienced the
    same problem you were facing. The fix is to supply an ID --this is because
    you are loading your controls at different locations like i stated.


    Private Sub Page_Load(ByVal sender As System.Object, ByVal e As
    System.EventArgs) Handles MyBase.Load
    If IsPostBack Then
    If Not viewstate("controls") Is Nothing Then
    LoadControls()
    End If
    End If
    End Sub

    Private Sub LoadControls()
    Dim control1 As Control
    Select Case RadioButtonList1.SelectedIndex
    Case 0
    control1 = LoadControl("webUserControl1.ascx")
    PlaceHolder1.Controls.Add(control1)
    control1.ID = "Mycontrol1"
    viewstate("controls") = 0
    Case 1
    control1 = LoadControl("webUserControl2.ascx")
    PlaceHolder1.Controls.Add(control1)
    control1.ID = "Mycontrol2"
    viewstate("controls") = 1
    End Select
    End Sub

    Private Sub RadioButtonList1_SelectedIndexChanged(ByVal sender As
    Object, ByVal e As System.EventArgs) Handles
    RadioButtonList1.SelectedIndexChanged
    Dim control1 As Control
    PlaceHolder1.Controls.Clear()
    LoadControls()
    End Sub


     
    Alessandro Zifiglio, Feb 2, 2004
    #5
  6. The Html view is :

    <body MS_POSITIONING="GridLayout">
    <form id="Form1" method="post" runat="server">
    <asp:radiobuttonlist id="RadioButtonList1" style="Z-INDEX: 103; LEFT:
    281px; POSITION: absolute; TOP: 270px" runat="server" AutoPostBack="True">
    <asp:ListItem Value="control1">control1</asp:ListItem>
    <asp:ListItem Value="control2">control2</asp:ListItem>
    </asp:radiobuttonlist><asp:placeholder id="PlaceHolder1"
    runat="server"></asp:placeholder>
    </form>

    Give it another try. It works :)

     
    Alessandro Zifiglio, Feb 2, 2004
    #6
  7. and to complete here is the code i used for the webUsercontrols. As you can
    see both have a click event that postsback.

    webUserControl1.ascx :

    <%@ Control Language="vb" AutoEventWireup="false"
    Codebehind="WebUserControl2.ascx.vb"
    Inherits="WebApplication1.WebUserControl2"
    TargetSchema="http://schemas.microsoft.com/intellisense/ie5" %>
    <h1 style="BACKGROUND-COLOR: #ffcc66">this is Control2
    <asp:Button id="Button1" Text="control 2" runat="server"></asp:Button></h1>

    webcontrol1.vb :
    Private Sub Button1_Click(ByVal sender As Object, ByVal e As
    System.EventArgs) Handles Button1.Click
    Response.Write("<h2>control2 fired</h2>")
    End Sub


    I have the same code for webUsercontrol2
     
    Alessandro Zifiglio, Feb 2, 2004
    #7
  8. Great. Its what i thought myself. Glad you got it working now :)
     
    Alessandro Zifiglio, Feb 3, 2004
    #8
  9. Shawn Meyer

    Shawn Meyer Guest

    I was trying to everything to fix the problem, and accidentally changed some
    important code. After fixing that problem, adding the ID worked
    beautifully, thanks alot. Sorry about the confusion.


     
    Shawn Meyer, Feb 3, 2004
    #9
  10. Shawn Meyer

    Earl Teigrob Guest

    Thanks, Alessando, this solved the same problem I have been trying to
    resolve for may hours. Yeah!!!
    (what in the H would a programmer do without newsgroups???)

    Earl

     
    Earl Teigrob, Feb 9, 2004
    #10
  11. lol Earl, I'm glad that helped you too :)
    Your right about the news groups. I'm addicted ;P
     
    Alessandro Zifiglio, Feb 9, 2004
    #11
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.