Question

Ajax with drop downlist

Asked by: R8VI

Hi,

I have the code below I am bascially making a call to the DB on selected index changed of the first drop down.

But nothing seems to get populated in the second drop down.

If I change thebut autopost true for first drop down it works fine but the whole page refreshes i dont want that

Please help

R8VI

aspx page 
 <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        Country
        <asp:UpdatePanel ID="UpdatePanel2" runat="server" UpdateMode="Always">
            <ContentTemplate>
                <asp:DropDownList ID="ddl_1" runat="server" OnSelectedIndexChanged="ddl_1_SelectedIndexChanged"
                    Width="171px">
                    <asp:ListItem>147</asp:ListItem>
                    <asp:ListItem>156</asp:ListItem>
                    <asp:ListItem>146</asp:ListItem>
                </asp:DropDownList>
            </ContentTemplate>
        </asp:UpdatePanel>
        <br />
        <br />
        City
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
                <asp:DropDownList ID="ddl_2" runat="server" Width="167px">
                </asp:DropDownList>
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="ddl_1" EventName="SelectedIndexChanged" />
            </Triggers>
        </asp:UpdatePanel>
    </div> 
c# 
       protected void ddl_1_SelectedIndexChanged(object sender, System.EventArgs e)
        { 
            if (!IsPostBack)
            {
                ddl_2.DataSource = BTU.GtByTForMl(int.Parse(ddl_1.SelectedItem.Value));
                ddl_2.DataBind();
            }
        }

                                  
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Asked On
2009-11-05 at 09:49:55ID24875324
Tags

c#

,

asp.net

Topics

.NET

,

C# Programming Language

,

Programming for ASP.NET

Participating Experts
3
Points
500
Comments
5

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Answers

 

by: burakiewiczPosted on 2009-11-05 at 09:58:22ID: 25752070

you have to set autopostback to true so it will fire the event.  whatever you dont want to refresh dont put in an update panel that is always set to refresh. you can set the update mode to conditional and call the Update() when you want it to refresh

 

by: silemonePosted on 2009-11-05 at 10:02:49ID: 25752117

you can:

make a clientevent for your dropdown

Ddl.Attributes.Add("onchange", "somefunction()");



have a hidden button on the page...usually you can just use a linkbutton and leave text blank...

now, whatever onselectionchanged event server code, place inside the linkbutton click event.

now, in javascript get instance of that button in the onchange event...and do something like this:  $get("linkbutton").click();

finally, make linkbutton a trigger event for the updatepanel...

 

by: silemonePosted on 2009-11-05 at 10:04:20ID: 25752128

oops...last but not least, return false after $get("linkbutton").click() so no postback will occur...

 

by: SheppePosted on 2009-11-05 at 17:03:12ID: 25755847

Move all of the controls that you want to give AJAX behaviour to into an UpdatePanel control, and then set their AutoPostback to true. What will happen instead of a postback (AKA: page reload) is an AJAX callback, with no page reload.

 

by: SheppePosted on 2009-11-05 at 17:04:02ID: 25755853

Sorry, I meant to say have them all in a *single* UpdatePanel.

20120131-EE-VQP-002

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