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问题:

I have a Textbox that changes the content of a dropdown in the OnTextChanged event. This event seems to fire when the textbox loses focus. How do I make this happen on the keypress or keyup event?

Here is an example of my code

<asp:TextBox ID="Code" runat="server" AutoPostBack="true" OnTextChanged="Code_TextChanged">                

<asp:UpdatePanel ID="Update" runat="server">
    <ContentTemplate>
        <asp:DropDownList runat="server" ID="DateList" />             
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="Code" />
    </Triggers>
</asp:UpdatePanel>

So in the codebehind, I bind the dropdown on page load. The Code_TextChanged event just rebinds the dropdown. I would like this to happen on each keypress rather than when the textbox loses focus.

I inherited this code recently and this is not the ideal method of doing this for me, but time limitations prevent me from rewriting this in a web servicy method.

I have tried using jQuery to bind the "keyup" event to match the "change" event for the textbox, but this only works on the first key pressed.

回答1:

This will solve your problem. Logic is same as the solution suggested by Kyle.

Have a look at this.

<head runat="server">
<title></title>
<script type="text/javascript">
    function RefreshUpdatePanel() {
        __doPostBack('<%= Code.ClientID %>', '');
    };
</script>

    <asp:TextBox ID="Code" runat="server" onkeyup="RefreshUpdatePanel();" AutoPostBack="true" OnTextChanged="Code_TextChanged"></asp:TextBox>
    <asp:UpdatePanel ID="Update" runat="server">
        <ContentTemplate>
            <asp:DropDownList runat="server" ID="DateList" />
            <asp:TextBox runat="server" ID="CurrentTime" ></asp:TextBox>
        </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="Code" />
        </Triggers>
    </asp:UpdatePanel>

Code behind goes like this...

 protected void Code_TextChanged(object sender, EventArgs e)
    {
        //Adding current time (minutes and seconds) into dropdownlist
        DateList.Items.Insert(0, new ListItem(DateTime.Now.ToString("mm:ss")));

        //Setting current time (minutes and seconds) into textbox
        CurrentTime.Text = DateTime.Now.ToString("mm:ss");
    }

I have added additional textbox to see change in action, do remove the textbox.

回答2:

Here is a simple way to do it with javascript, an update panel, gridview, sqldatasource and a textbox. As you type it searches the table and displays the results. Short and sweet, no code behind.

<%@ Page Language="VB" AutoEventWireup="false" CodeFile="test3.aspx.vb" Inherits="test3" %>

<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="asp" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
 <script type="text/javascript">
     function runPostback() {
         document.forms["form1"].submit();
         document.getElementById("TextBox1").focus();
     }
     function getFocus(){
         var text = document.getElementById("TextBox1");
         if (text != null && text.value.length > 0) {
             if (text.createTextRange) {
                 var FieldRange = text.createTextRange();
                 FieldRange.moveStart('character', text.value.length); 
                 FieldRange.collapse();
            FieldRange.select(); } }
}

function SetDelay() {
    setTimeout("runPostback()", 200);
}




 </script>
</head>
<body onload="getFocus()">
<form id="form1" runat="server">
<div>
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
    <asp:UpdatePanel ID="UpdatePanel1" runat="server">
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="TextBox1" />
        </Triggers>
        <ContentTemplate>
            <asp:TextBox ID="TextBox1" onkeyup="SetDelay();" runat="server"></asp:TextBox>
            <asp:GridView ID="GridView1" runat="server" DataSourceID="SqlDataSource1">
            </asp:GridView>
            <asp:SqlDataSource ID="SqlDataSource1" runat="server" ConnectionString="<%$ ConnectionStrings:purchasing2ConnectionString %>"
                SelectCommand="SELECT [name] FROM [vendors] WHERE ([name] LIKE  @name + '%')">
                <SelectParameters>
                    <asp:ControlParameter ControlID="TextBox1" Name="name" PropertyName="Text" Type="String" />
                </SelectParameters>
            </asp:SqlDataSource>
        </ContentTemplate>
    </asp:UpdatePanel>
</div>
</form>

回答3:

Would this help you?

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

回答4:

I use a javascript trick for trigger a OnTextChanged event, i call a blur function and than re-focus the input text (or, if you have many input text, switch focus from two input text)

I have test it in IE and Firefox.

javascript code:

function reFocus(id) 
    {
        document.getElementById(id).blur();
        document.getElementById(id).focus();
    }

aspx code

<asp:TextBox ID="txtProdottoLike" runat="server"
                ontextchanged="txtProdottoLike_TextChanged"
                onKeyUp="reFocus(this.id);" 
                AutoPostBack="True">
</asp:TextBox>

<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>                
<asp:UpdatePanel ID="Update" runat="server">
    <ContentTemplate>
        <asp:GridView ID="GridProdotto" runat="server" AllowPaging="False" 
                AllowSorting="False" ForeColor="#333333" GridLines="None"
            OnSelectedIndexChanging="GridProdotto_SelectedIndexChanging"
            Visible="True"  Width="100%" Height="100%" AutoGenerateColumns="False">
            <RowStyle BackColor="WhiteSmoke" Font-Size="11px" />
            <AlternatingRowStyle BackColor="White" />
            <Columns>
                <asp:BoundField DataField="Prodotto">
                    <ItemStyle Width="80px" HorizontalAlign="Left" />
                    <HeaderStyle HorizontalAlign="Left" />
                </asp:BoundField>
                <asp:BoundField DataField="Descrizione">
                    <ItemStyle HorizontalAlign="Left" />
                    <HeaderStyle HorizontalAlign="Left" />
                </asp:BoundField>
                <asp:CommandField SelectText="Seleziona" ShowSelectButton="True" ItemStyle-HorizontalAlign="Right"></asp:CommandField>
            </Columns>
        </asp:GridView>
    </ContentTemplate>
    <Triggers>
        <asp:AsyncPostBackTrigger ControlID="txtProdottoLike" />
    </Triggers>
</asp:UpdatePanel>

The c# function "GridProdotto_SelectedIndexChanging" retrive data from database and build the grid.