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assigning value to hidden field from javascript

I am trying to do what seems to be simple but am unable to accomplish
I am trying to set the value of a column after a row focus change in a grid to a hidden value in java script.
My imbedded javascript code:
function OnGridFocusedRowChanged() {
grdA.GetRowValues(grdA.GetFocusedRowIndex(), 'ClientID', OnGetRowValues);
}
function OnGetRowValues(values) {
//Set hidden value
document.getElementById('<%=hdnClientID.ClientID%>').value = values[0];
//Fire button click
btnPopulateGrids_Click();
}
where hdnClientID is the name of my hidden field
In GridA I have the setting as such that OnGridFocusedRowChanged gets executed each time a row focus change takes place.
To this point, it works fine, the values[0] in OnGetRowValues() contains the correct value from the corresponding row in GridA.
But in the corresponding code behind, I cannot access the value from hidden field hdnClientID. Always comes up null when accessing
Current_Client_ID = CInt(hdnClientID.Value);
cannot access or convert any value from
hdnClientID.ClientID.
either.
I'm missing something simple.

I had to complete a similar task recently and I too was unable to access the value from codebehind. I researched and found out that it is not that simple and that you can't do it with javascript. What I would recommend is to check if you have jQuery installed and if you do, change your function to this:
function OnGetRowValues(values) {
//Set hidden value
$('#<%=hdnClientID.ClientID%>').val(values[0]);
//Fire button click
btnPopulateGrids_Click();
//If you change your HiddenField to have OnValueChange event, you can trigger it with this
//__doPostBack('<%= CompanyCode.ClientID %>', '');
}
Also, I guess you are firing some function from code behind with btnPopulateGrids_Click();.
I would recommend adding OnValueChanged="hdnClientID_OnValueChanged"/> to your <asp:HiddenField/> and using my supplied function triggering method.

How to read text box text set by JavaScript from code behind?

I have one ASP.net text box on my page. I am setting text property of this text box using JavaScript. Now, I want to access this text value from back-end (using C#). However, whenever I try to access it, I am getting the old value (the one set up during page load) and I am not able to get the value set by JavaScript code.
Am I missing something here?
ASPX markup of the text box -
<asp:TextBox ID="txtMessage" runat="server"></asp:TextBox>
JavaScript to edit this text box -
var txtMessage = document.getElementById("txtMessage");
txtMessage.Value = "New Value";
C# code to access text box text -
string strMessage = txtMessage.Text; // This does not return value set by above JS function

You just have to change this line in the JavaScript:
txtMessage.value = "New Value"; // the "v" in ".value" needs to be lowercase
UPDATE: I set up an ASP.NET page to make sure that the OP's code did in fact work with that one change, just to make sure I wasn't missing any other little typo. However, as Igor pointed out in his comment, it's a good practice to use the control's ClientID property to account for any prefixes that the .NET runtime might add to an HTML element's id.
So the two lines in your JavaScript should be changed to this (also confirmed to work correctly):
var txtMessage = document.getElementById("<%= txtMessage.ClientID %>");
txtMessage.value = "New Value";

When ASP.Net delivers the page to be render, the name of the controls are changed by prepending a suffix that identifies the container that hold them. From JavaScript, you must ensure to get the correct ID of ASP controls by accessing the .ClientID property.
//gets the element by its ID according to ASP rules
var txtMessage = document.getElementById("<%=txtMessage.ClientID%>");
//the "value" property is lowercase
txtMessage.value = "New Value";

Setting Default value of input textbox in Jquery EasyUI dialog

I have googled and looked throughout the whole documentation and could not figure out why value of input text is not shown. I am using FireFox latest version and below is what I have done so far.
<input name="amount" class="easyui-validatebox" id="d_amount" value="">
In regular html or php page we can give value="300" to set default value, but in EasyUI, it is not possible. So I was thinking possible alternative like below:
<script>
var m = '300';
document.getElementById("d_amount").value.innerHTML=m;
</script>
Nothing is shown and I am not getting any error. Any EasyUI expert, please help me.
NOTE: this input field is inside the dialog

To set the default value, you have to set the value attribute. However, that does not necessarily update the value property so you need to do both. So given:
<input name="amount" class="easyui-validatebox" id="d_amount" value="">
set the default value by setting the value attribute:
var input = document.getElementById('d_amount')
input.setAttribute('value', 'whatever');
now set the value property:
input.value = 'whatever';
Note that you can also get a reference to the input as a member of the form that it's in:
var input = document.formName.d_amount;

Use the below code
$("#d_amount").numberbox({
min:0,
precision:2,
value:300
})
Reference : numberbox
Or try this one
$("#d_amount").textbox({
buttonText:'Search',
iconCls:'icon-man',
iconAlign:'left',
value:"300"
});
Reference : textbox

use this code to set the value inside $(document).ready(function(){}
....
$("#d_amount").numberbox('setValue','300');
....
if still not working, just try to set name and id as the same name and id
<input name="d_amount" class="easyui-validatebox" id="d_amount" value="">
I am always working with this numberbox and it's working

I have found your thread because I am also having the same issue and I have just across this thing today. Your case is a little bit different (maybe) then my case because you want to set the default which can be changed by the user later (I believe). In my case, the value will be fixed (will not be changed) so I have applied a trick and hopefully it can give some ideas to you and others who are having same issue. Please refer below:
In first page says pageA.php:
<select name="myThing" id="myThing">
<option value="Your Desired Value" selected="selected">Something</option>
</select>
Still in the same page, under your $(document).ready( function(){ put the code below:
$("#myThing").val($("#myThing option:first").val());
That code is to make sure your desired value appears at the first row in the drop down. I say this because in EasyUI it seems when I use drop down and put single option, the first row will be blank and the second row will hold your input. So that is the trick to ensure your desired value appears on top and selected. Put the select under the form then during normal post, you will be able to get the value of it in the posted page. Enjoy. Thank you.
Suggestion: if your value can be changed by user, use placeholder and you can hide the default value from user using my trick.

try this
document.getElementById("d_amount").value=m;
you don't need innerHTML

I found the answer here. The trick is to use the code inside $(function(){});
$(function(){
var m=300;
$('#d_amount').textbox('setValue', m);
});

I too had this problem and it was solved using the following
First my input was in the form like this:
<input name="hostFirstName" id="hostFirstName" class="easyui-textbox">
I needed to load content from the db then pre-fill the input with this data so the user could edit the content.
I used the following javascript.
NOTE: i didn't hide this away inside an anonymous function() and it is working. I tested this first from the F12 console to make sure it was working before changing my code.
//populate with existing data
$('#hostFirstName').textbox('setValue', "Is this working?");
The docs on jeasyui.com don't provide this example when you look at the textbox api reference. But they do provide an example when looking at the combobox (http://www.jeasyui.com/documentation/index.php#) the combobox and textbox use the same setValue method.
Hopefully this works for you like it does for me.

Using telerik radgrid itemcommand with a radwindow to get initial data for InsertMode Dropdowns

I need some assistance with the telerik radgrid's itemcommand to get some information from a user adding a new record prior to opening the Grid in Insert mode. I have the itemcommand working to open a radwindow, present the user with a dropdown list of items to select from and a radbutton to select the value and close the radwindow, then this value is passed back to the parent page in javascript. All the values are passed down and I can use the alert function to validate this.
So at this point I need to continue the flow to open the radgrid in insert mode and filter a dropdown in the insertmode using the value from the radwindow noted above. In order to use this value I'm attempting to assign it to a hidden radtextbox for use in the ItemDatabound event when the form is loading in insert mode. Unfortunately, the value isn't being set via the javascript in this hidden control and is acting like it is erroring somewhere in the javascript. I feel like I'm overcomplicating this but was hoping for some guidance on what others have done to implement something like this.
<asp:LinkButton ID="addNewRecord" runat="server" Text="Add New Record" OnClientClick="openWin(); return false;" OnClick="InitInsert">Add New Record</asp:LinkButton>
<telerik:RadCodeBlock ID="RadCodeBlock1" runat="server">
<script type="text/javascript">
//<![CDATA[
function openWin(sender, args) {
var oWnd = radopen("ParserFileNewDialog.aspx", "RadWindow1");
}
function OnClientClose(oWnd, args) {
//get the transferred arguments
var arg = args.get_argument();
if (arg) {
var lenderid = arg.LenderID;
var tb = null;
tb = $find("<%=newLenderID2.ClientID %>");
alert(tb.get_text());
tb.set_text(lenderid);
$find("<%=hdnInsertBtn2.ClientID %>").click();
}
}
//]]>
</script>
</telerik:RadCodeBlock>
Any help is greatly appreciated!

What type of control is the newLenderID2 that you attempt to set a value to? With this syntax, it should be a RadTextBox. If it is an asp:HiddenFiel, you need
$get("<%=newLenderID2.ClientID %>").value = lenderid;
If you get an error - what is the error?
Also, you can fire a grid command and pass an argument to it (depending on the command) directly via the grid's masterTableView client-side API and the fireCommand() method: http://www.telerik.com/help/aspnet-ajax/grid-gridtableview-firecommand.html. Thus, you may not need the hidden button at all. A hidden field will suffice for data transmission.

Jquery Not able to fetch changed value of input field

I am trying to fetch the changed input filed value using jquery which is getting changed javascript event of drop down select.
I simply am not getting where exactly the things are getting wrong. It is something related to dom tree refresh (.live)? Any help/suggestions would be great. Thanks.
/* adding the value to user_val input field id in javascript onload function based on drop down select event*/
document.getElementById('user_val').Value = "abcd";
/* then trying to get value which changed */
$(document).ready(function() {
$("#submits").click(function() {
alert($("#user_val").val());
});

You haven't closed your click event handler function. Change it to this:
$(document).ready(function() {
$("#submits").click(function() {
alert($("#user_val").val());
});
});
And change Value to value (note the lowercase "v"), and then it should work fine.

Two errors you got there:
You should use document.getElementById('user_val').value = "abcd"; and not document.getElementById('user_val').Value = "abcd"; (lower case value, not Value).
You should also close the ready event after your click event.
Here is the complete working solution:
/* adding the value to user_val input field id in javascript onload function based on drop down select event*/
document.getElementById('user_val').value = "abcd";
/* then trying to get value which changed */
$(document).ready(function() {
$("#submits").click(function() {
alert($("#user_val").val());
});
});