How to make an ASP.NET TextBox fire it's onTextChanged event fire in an AJAX UpdatePanel?

Question

I am trying to get an textBox to fire it's onTextChanged event every time a keystroke is made rather than only firing only when it looses focus. I thought that adding the AsyncPostBackTrigger would do this but it's still not working. Is what I'm trying to do even possible? The code is below:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Items.aspx.cs" MasterPageFile="~/MMPAdmin.Master" Inherits="MMPAdmin.Items" %>
<asp:Content ID="content1" runat="server" ContentPlaceHolderID="ContentPlaceHolder1">
<asp:ScriptManager ID="sm_Main" runat="server" />
    <div style="left:10px;position:relative;width:100%;overflow:hidden">
        <asp:UpdatePanel ID="up_SearchText" runat="server">
            <Triggers>
                 <asp:AsyncPostBackTrigger ControlID="tb_Search" EventName="TextChanged" />
            </Triggers>
            <ContentTemplate>
                <div style="position:relative;float:left">
                    <b style="font-size:xx-large">Items</b>(<a href="Item.aspx">Add New</a>)
                </div>
                <div style="right:25px;position:absolute; top:30px">
                    Search: <asp:TextBox ID="tb_Search" runat="server" Width="200" OnTextChanged="UpdateGrid" AutoPostBack="true" />
                </div>
                <br />
                <div>
                    <asp:GridView runat="server" AutoGenerateColumns="true" ID="gv_Items" AutoGenerateEditButton="true" AutoGenerateDeleteButton="true" />
                </div>
            </ContentTemplate>
        </asp:UpdatePanel>
    </div>
</asp:Content>

Answer 1

All the AsyncPostBackTrigger does is make sure only that portion of the page refreshes when the event is fired, it does not change when the event is fired.

I think it's possible to do what you want, but you'd need to write some javascript code to manually fire the event... and I don't even want to think about making that work.

Answer 2

You need to call the _postback() function for your textbox control when the onkeyup is raised raised using javascript. However, since your textbox is inside your update panel, the textbox will get re-rendered everytime the user hits a key, causing the cursor to loose focus. This will not be usable unless you get your textbox out of the the updatepanel. That may work out for you, as update panels tend to be a bit slow, you may still have usability issues. I would suggest using an autocomplete component (there is one in the asp.net control toolkit or you could use the jquery autocomplete plugin which I have found to be a bit better).