change textbox value in client side and read it in server side

Question

I have some textbox and I change the value of this textboxes in clientside (javascript) ,value was changed but when I read in server side after postback actually value not changed. my textbox isn't read only or disable. notice that I use updatepanel and my postbacks is async.any idea to solve this issue?

update I use this jquery to support placeholder in ie,but it cause value of my textboxes equal to placeholder value, and this conflict when my postback is async. for solving this problem I use below jquery code:

function EndRequestPostBackForUpdateControls() {
//*****************************For place holder support in ie******************************
if (runPlaceHolder != 0) {
    //alert('end');
    $('input, textarea').placeholder();


    var $inputs = $('.placeholder');
    $inputs.each(function () {

        var $replacement;
        var input = this;
        var $input = $(input);
        var id = this.id;
        if (input.value == '') {
            if (input.type == 'password') {
                if (!$input.data('placeholder-textinput')) {
                    try {
                        $replacement = $input.clone().attr({ 'type': 'text' });
                    } catch (e) {
                        $replacement = $('<input>').attr($.extend(args(this), { 'type': 'text' }));
                    }
                    $replacement
                    .removeAttr('name')
                    .data({
                        'placeholder-password': $input,
                        'placeholder-id': id
                    })
                    .bind('focus.placeholder', clearPlaceholder);
                    $input
                    .data({
                        'placeholder-textinput': $replacement,
                        'placeholder-id': id
                    })
                    .before($replacement);
                }
                $input = $input.removeAttr('id').hide().prev().attr('id', id).show();
                // Note: `$input[0] != input` now!
            }
            $input.addClass('placeholder');
            $input[0].value = $input.attr('placeholder');
        } else {
            $input.removeClass('placeholder');
        }
    });
}}
function safeActiveElement() {
// Avoid IE9 `document.activeElement` of death
// https://github.com/mathiasbynens/jquery-placeholder/pull/99
try {
    return document.activeElement;
} catch (err) { }}

function BeginRequestPostBackForUpdateControls() {
//*****************************For place holder support in ie******************************
if (runPlaceHolder != 0) {
    // Clear the placeholder values so they don't get submitted
    var $inputs = $('.placeholder').each(function () {
        var input = this;
        var $input = $(input);
        if (input.value == $input.attr('placeholder') && $input.hasClass('placeholder')) {
            if ($input.data('placeholder-password')) {

                $input = $input.hide().next().show().attr('id', $input.removeAttr('id').data('placeholder-id'));
                // If `clearPlaceholder` was called from `$.valHooks.input.set`
                if (event === true) {
                    return $input[0].value = value;
                }
                $input.focus();
            } else {
                alert($(this)[0].value);
                $(this)[0].value = '';
                alert($(this)[0].value);
                $input.removeClass('placeholder');
                input == safeActiveElement() && input.select();
            }
        }
    });
}}

$(document).ready(function () {

    var prm = Sys.WebForms.PageRequestManager.getInstance();
    prm.add_beginRequest(BeginRequestPostBackForUpdateControls);

    prm.add_endRequest(EndRequestPostBackForUpdateControls);

});

I use this code to clear my textbox value before sending to server in add_beginRequest,and set value in add_endRequest (for placeholder in ie). can anyone help solve this problem? thank you.

Answer 1

You changed the value of TextBox with javascript and the respective ViewState is not updated. You can use hidden field to store the value in javascript and get it in code behind.

Html

<input type="hidden" id="hdn" runat="server" />

JavaScript

document.getElementById("hdn").value = "your value";

Code behind

string hdnValue = hdn.Value;

Answer 2

使用隐藏字段存储值，并在服务器端检索它。