Set focus in TextBox after postback

I have a simple page where I want to filter a ListBox based upon a value(s) in a textbox – both are in an UpdatePanel.
This works correctly, however, after the postback the textbox had lost focus…so I set focus back in the page_load.
Then I noticed that the cursor was now at the beginning of the text when I want it at the end so the user can carry on typing, so I added an onfocus(…) attribute to the textbox to set the value back to itself (see code below).

This works the first two times, but then it stops setting focus to the textbox?


<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="ListTest.aspx.cs" Inherits="SalesForceTest.ListTest" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "">
<html xmlns="">
<head runat="server">
    <form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server" LoadScriptsBeforeUI="true"/>
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
                <asp:TextBox runat="server" ID="filter" AutoPostBack="true" onkeyup="__doPostBack(, this.value)" onfocus="this.value = this.value;"  />
                <br />
                <asp:ListBox ID="AccountList" runat="server" Width="185px"></asp:ListBox>


using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Text;

namespace SalesForceTest
    public partial class ListTest : System.Web.UI.Page
        List<string> allAccounts = new List<string> { "2342", "3434", "2332", "3224", "7899", "8797", "3435" };

        protected void Page_Load(object sender, EventArgs e)
            allAccounts.Where(ac => ac.StartsWith(filter.Text)).ToList().ForEach(a => AccountList.Items.Add(a));

            if (Page.IsPostBack)
                if (Request.Form["__EVENTTARGET"] == filter.ID)

Any help VERY gratefully received 🙂

Here is Solutions:

We have many solutions to this problem, But we recommend you to use the first solution because it is tested & true solution that will 100% work for you.

Solution 1

You need to set the cursor/caret position at the end of text using java-script. Use below js function for the setting cursor position:

function setCaretTo(obj, pos) { 
    if(obj.createTextRange) { 
        /* Create a TextRange, set the internal pointer to
           a specified position and show the cursor at this
        var range = obj.createTextRange(); 
        range.move("character", pos);; 
    } else if(obj.selectionStart) { 
        /* Gecko is a little bit shorter on that. Simply
           focus the element and set the selection to a
           specified position
        obj.setSelectionRange(pos, pos); 

source for above code:

Now, what you need is ref to your client-side textbox object (document.getElementById) and text length (textbox.value.length). Call the function in the start-up script (registered via ScriptManager.RegisterStartupScript) method.

Note: Use and implement solution 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from or, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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