This is a migrated thread and some comments may be shown as answers.

ComboBox not firing events

5 Answers 150 Views

ComboBox

This is a migrated thread and some comments may be shown as answers.

StephenWRogers asked on 11 Jul 2008, 09:11 AM

I'm having a problem since upgrading from 2008.1.415 to 2008.1.619 with a ComboBox not firing the SelectedIndexChanged event.

I traced it back to the ClientID of the combobox having changed since the new version - where previously it was the full control hierarchy eg mainPlaceHolder$cplTopPaneContent$frmSalaryHistory$gradeSelector$dropDown it is now being rendered as just gradeSelector$dropDown.

Having spent a while debugging the new version, i think the problem lies with the new CreateHeader and CreateFooter methods:

    
                    private void CreateFooter() 
        
                    { 
        
                        if (_footer == null) 
        
                        { 
        
                            this._footer = new RadComboBoxHeaderFooterControl(); 
        
                            this.Controls.Add(Footer); 
        
                            Footer.ID = this.ClientID + "_Footer"; 
        
                            Footer.CssClass = RadComboBox.FooterCssClass; 
        
                        } 
        
                    } 
        
                    private void CreateHeader() 
        
                    { 
        
                        if (_header == null) 
        
                        { 
        
                            this._header = new RadComboBoxHeaderFooterControl(); 
        
                            this.Controls.Add(Header); 
        
                            Header.ID = this.ClientID + "_Header"; 
        
                            Header.CssClass = RadComboBox.HeaderCssClass; 
        
                        } 
        
                    }

These methods make a reference to this.ClientID, and as they are being called while the control hierarchy is not yet finalised they can cause problems with caching of UniqueIDPrefixes for the controls.

This results in the controls being rendered with the wrong clientIDs and the events not firing. This is discussed on pages such as http://dotnetslackers.com/DataGrid/re-49612_Accessing_ClientID_or_UniqueID_too_early_can_cause_issues.aspx

It's not easy to reproduce this in a small project, as I think the control has to be in a nested hierarchy before it starts breaking, but if you just want the header to have the same ClientID as the combobox, but with "_Header" suffixed to it, is it not possible to change the above code to

    
                    private void CreateFooter() 
        
                    { 
        
                        if (_footer == null) 
        
                        { 
        
                            this._footer = new RadComboBoxHeaderFooterControl(); 
        
                            this.Controls.Add(Footer); 
        
                            Footer.ID = "_Footer"; 
        
                            Footer.CssClass = RadComboBox.FooterCssClass; 
        
                        } 
        
                    } 
        
                    private void CreateHeader() 
        
                    { 
        
                        if (_header == null) 
        
                        { 
        
                            this._header = new RadComboBoxHeaderFooterControl(); 
        
                            this.Controls.Add(Header); 
        
                            Header.ID = "_Header"; 
        
                            Header.CssClass = RadComboBox.HeaderCssClass; 
        
                        } 
        
                    }

and ASP.NET will take care of prefixing with the combobox's ID (as the header is a child control of the combobox)?

Thanks,

Stephen

5 Answers, 1 is accepted

answered on 14 Jul 2008, 01:16 PM

Hi,

The problem with the SelectedIndexChanged event is exactly to do with the code in CreateHeader and CreateFooter - that was the point of my email.

Try the following example:

ASPX

    
            <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %> 
        
            <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> 
        
            <html xmlns="http://www.w3.org/1999/xhtml"> 
        
            <head runat="server"> 
        
                <title>Untitled Page</title> 
        
            </head> 
        
            <body> 
        
                <form id="form1" runat="server"> 
        
                    <asp:ScriptManager ID="ScriptManager1" runat="server" /> 
        
                    <div> 
        
                    <asp:DataGrid ID="DataGrid1" runat="server"  AutoGenerateColumns="false" OnItemCreated="DataGrid1_ItemCreated" > 
        
                 <Columns> 
        
                    <asp:TemplateColumn> 
        
                       <ItemTemplate> 
        
                         <telerik:RadComboBox AutoPostBack="true" runat="server" ID="combo" OnSelectedIndexChanged="combo_SelectedIndexChanged"> 
        
                         </telerik:RadComboBox> 
        
                       </ItemTemplate> 
        
                    </asp:TemplateColumn> 
        
                 </Columns> 
        
                 </asp:DataGrid> 
        
                    </div> 
        
                </form> 
        
            </body> 
        
            </html>

    
            using System; 
        
            using System.Data; 
        
            using System.Configuration; 
        
            using System.Web; 
        
            using System.Web.Security; 
        
            using System.Web.UI; 
        
            using System.Web.UI.WebControls; 
        
            using System.Web.UI.WebControls.WebParts; 
        
            using System.Web.UI.HtmlControls; 
        
            using System.Net; 
        
            using System.Collections.Generic; 
        
            using Telerik.Web.UI; 
        
            public partial class _Default : System.Web.UI.Page  
        
            { 
        
                protected void Page_Load(object sender, EventArgs e) 
        
                { 
        
                    if (!Page.IsPostBack) 
        
                    { 
        
                        List<int> list = new List<int>(); 
        
                        list.Add(1); 
        
                        list.Add(2); 
        
                        list.Add(3); 
        
                        DataGrid1.DataSource = list; 
        
                        DataGrid1.DataBind(); 
        
                    } 
        
                } 
        
                protected void combo_SelectedIndexChanged(object o, RadComboBoxSelectedIndexChangedEventArgs e) 
        
                { 
        
                    //put a breakpoint here; 
        
                } 
        
                protected void DataGrid1_ItemCreated(object sender, DataGridItemEventArgs e) 
        
                { 
        
                    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem) 
        
                    { 
        
                        //Touching the clientID too early causes rendered ids to be wrong 
        
                        // which also impacts on postback routing etc etc 
        
                        RadComboBox combo = e.Item.FindControl("combo") as RadComboBox; 
        
                        List<int> list = new List<int>(); 
        
                        list.Add(1); 
        
                        list.Add(2); 
        
                        list.Add(3); 
        
                        combo.DataSource = list; 
        
                        combo.DataBind(); 
        
                    } 
        
                } 
        
            }

It's essentially just the example from the page I linked to, but with your ComboBox in the ItemTemplate.

Try that with version 1.619 and you'll see all the comboboxes are rendered with id="combo_Input", and hence the event doesn't fire and the inputs don't retain their values properly.

Then change the two lines

    
            Footer.ID = this.ClientID + "_Footer"; 
        
            Header.ID = this.ClientID + "_Header";

    
            Footer.ID = "Footer"; 
        
            Header.ID = "Header";

and try again. This time the ClientIDs aren't accessed before the control hierarchy has finalised, the ids are correctly set (eg "DataGrid1_ctl02_combo_Input"), and the events fire correctly.

It's quite a big problem with our site at the moment, CreateHeader and CreateFooter are fired whenever the combobox is created and if the control hierarchy is not finalised (as in the pretty simple example above), they stop working.

Thanks,

Stephen

Accepted

answered on 15 Jul 2008, 10:01 AM

Telerik.Web.UI_2008_1_715_trial_hotfix.zip

Hi ,

Please find the attached internal build where the change is implemented and let us known how this goes.

Regards,
Rosi
the Telerik team

Instantly find answers to your questions at the new Telerik Support Center

Product Bundles

DevCraft

Web

Mobile

Document Management

Desktop

Reporting & Mocking

Automated Testing

CMS

UI/UX Tools

Debugging

Free Tools

Support and Learning

Productivity and Design Tools

ComboBox not firing events

5 Answers, 1 is accepted