Access javascript document in asp.net code behind - javascript

I am trying to access javascript document from ASP.net page code behind. How do I do same thing as below in c# code behind?
document.getElementById(id).src = "myurl.com"
Thank you for your help.

Add runat="server" and an ID to the element. You should then be able to access the src via the attributes collection.
<img src="http://www.google.com/img.png" id="imgGoogle" runat="server" />
Dim src as String = imgGoogle.Attributes("src")

Related

How to get Asp.Net GridView control ID in Javascript

I did try searching and I tried all the solution provided and I still cannot get this to work, the javascript is returning null for while trying to get the element ID of the grid view. How can I get the client ID of the gridview, from the web browser it is showing as --> id="ctl00_ContentPlaceHolder1_GridView5"
function Validate() {
var GridID = document.getElementById('<%= GridView5.ClientID %>');
alert(GridID);
}
<asp:GridView ID="GridView5" runat="server" OnRowDataBound="GridView5_RowDataBound" AutoGenerateColumns = "False" HorizontalAlign="Center">
What am I doing that's wrong?
Please try this,
var grid = $("[id*=GridView5]")
or use
var grid = $("#<%=GridView5%>")
write this line in current page script
As the Javascript code is in the external file, you cannot use <%= GridView5.ClientID %> expression.
I would suggest you to set the GridView.ClientIDMode="Static" and use the below code to acces gridview in external javascript file.
if this is your gridview
<asp:GridView ID="GridView5" runat="server" OnRowDataBound="GridView5_RowDataBound" AutoGenerateColumns = "False" HorizontalAlign="Center" ClientIDMode="Static">
then use theblow code
var grid = $("#GridView5");
thank you for the suggestion. This worked for me as my java scripts are in a separate file.
var tbl = document.getElementById("GridView5");

ddl is not updated in server - asp.net

I work on ASP.NET c#. I have a DropDownList. (runat="server")
On $(document).ready, I updated its value:
$(document).ready(function () {
document.getElementById("ddl").value = "abc";
…
When I get back to the Server (c#), there is no value in the ddl:
ddl.SelectedValue == ""
What could be the problem?
Thanks,
YYY
as far your dropdown runat="server" it has generated ClientID, "ddl" it's serverside id, on client you need to call like shown below
document.getElementById("<%= ddl.ClientID %>").value = "abc";
Welcome to the wonderful world of WebForms: in the list of things this framework screws up is ID's of your runat="server" elements
When the engine processes your server markup it generates own id's based on the place where you declared that particular element. Check it in your browser devtools.
Luckily since ASP.NET 4 you can specify special attribute ClientIDMode and now you can do it like
<asp:TextBox ID="txt" runat="server" ClientIDMode="Static" />
which will render like
<input id="txt" name="ctl00$MasterPageBody$ctl00$txt" />
If you cannot use for some reason ASP.NET 4, you can stick to old solution as #Dan proposed:
document.getElementById("<%= ddl.ClientID %>")
But this is not the recommended way.
EDIT
Probably you should do ddl.SelectedItem.Value instead.

How to get javascript and jQuery variable in code behid in asp.net C#

I want otdval at code behind in asp.net C#
otdval = (parseFloat(otdval) + parseFloat(saletax)); // duesignmain;
$("#lblotd").text(String(Math.round(otdval)).replace(/(\d)(?=(\d\d\d)+(?!\d))/g,"$1,"));
Store otdval variable value in hidden field and retrieve in code behind.
In aspx create a hidden field
<asp:HiddenField id="hdnField" runat="server" />
In JavaScript
document.getElementById('hdnField').value = otdval;
In JQuery
$('input:hidden[id*=hdnField]').val(otdval);
In Codebhind
string otdvalValue = hdnField.Value;

Converting aspx page to WebUserControl

I am running into an issue when converting an ASPX page to a controller (ASCX). My JavaScript isn't finding a textbox in a hidden div and its not firing an onclick event either. However it works perfectly fine in the ASPX page.
My JavaScript is..
function FireEditClickButton() {
document.getElementById("btnFireEdit").click();
}
Its supposed to fire this button that is in a hidden div along with the next piece)
<asp:Button ID="btnFireEdit" runat="server" OnClick="btnFireEdit_Click" />
Then with this JavaScript
function GetSelection() {
var c = document.getElementById("tbRA");
c.innerText = checkListBox.GetSelectedValues();
UpdateText();
}
gets called everytime the checklistbox has values.
Both errors are saying that they are null but they are right here in a hidden div
<div style="visibility: hidden">
<asp:TextBox ID="tbRA" runat="server"></asp:TextBox>
<asp:Button ID="btnFireEdit" runat="server" OnClick="btnFireEdit_Click" />
</div>
So why would this be happening since it works completely fine in the ASPX page? would it have to do with the WebUserControl not using a form tag?
Thanks
Your javascript cannot find the button because in the rendered HTML it no longer has id="btnFireEdit" but instead an id based on the name of the usercontrol (e.g. id="myctrlname_btnFireEdit").
You have two choices... either update the javascript to include the name of the usercontrol...
document.getElementById("myctrlname_btnFireEdit").click();
document.getElementById("<%=btnFireEdit.ClientID%>").click();
(Note, the 2nd of these two lines will only work if the javascript is part of the usercontrol itself. It will not work if the javascript is in an external .js file or the parent page)
Or use the ClientIDMode attribute of the <asp:Button> and set the value to Static. This will make the rendered HTML use id="btnFireEdit"...
<asp:Button ID="btnFireEdit" runat="server" OnClick="btnFireEdit_Click"
ClientIDMode="Static" />
When using nested controls (or pages nested in a master page), by default the ID on the client side will be different than on the server. ASP.NET does this by default to help ensure that all ID's on the client are unique. However, you can prevent this using one of two ways.
The first option is to change the ClientIDMode to static. You can do this at the control, page, web.config, or machine.config levels. The web.config technique is shown below. The ID on the client will then match the ID on the server.
<configuration>
<system.web>
<pages clientIDMode="static" />
</system.Web>
</configuration>
The second option is to use inline C# code to embed the ID into your JavaScript, but this only works if the JavaScript is embedded on an ASP.NET page or control and not in a separate script file. The C# expression will be evaluated and therefore the ID on the client will be embedded into the JavaScript.
document.getElementById('<%= btnFireEdit.ClientId %>');
There is a third option, and that is to figure out what the ID will be on the client and then manually put that in the JavaScript, like this:
document.getElementById("myctrlname_btnFireEdit").click();
However, that is a bad idea. If you ever rename either myctrlname or btnFireEdit then your client side code will fail at runtime. And it's always better to fail at compile time than runtime.

getElementById not finding control generated by ASP.net

I am simply trying to store a label in a variable in javascript but for some reason this isn't working with document.getElementById('control');. I know my javascript is linking to my html file fine because everything else works.
Here is my javascript code:
function performEvapCooledCircuit(txt)
{
var error = document.getElementById('lblError');
if (txt.value == null || isNaN(txt.value))
{
error.style.visibility = "visible";
}
}
Here is the html code for my label:
<asp:Label ID="lblError" class="NormLabel" runat="server"
style="color:red; visibility:hidden;" Text="Invalid Input."></asp:Label>
I am getting an error that says object expected??
The ID that ASP.NET will generate will not be "lblError" so you'll need to reference it by its ClientID
document.getElementById('<%=lblError.ClientID %>');
If your javascript file is external I've usually had to write a type of "Init" javascript method to make sure my ID's were set up property
On your ASPX page:
<script type="text/javascript">
var lblError = null;
function InitializeVariables()
{
if (lblError == null) // make sure you only do this once
{
lblError = document.getElementById("<%=lblError.ClientID %>");
}
}
</script>
<asp:Label
ID="lblError"
class="NormLabel"
runat="server"
style="color:red; visibility:hidden;"
Text="Invalid Input."></asp:Label>
Then in your javascript file you'll have to call InitializeVariables() to make sure you've got the variables pointing to the proper asp.net controls
function performEvapCooledCircuit(txt)
{
InitializeVariables();
if (txt.value == null || isNaN(txt.value))
{
lblError.style.visibility = "visible";
}
}
"hunter" gives a pretty solid way of doing things, however a, in my opinion far better method is to use the "CliendIDMode" property on the control and set that property to "Static". This will make the client and server IDs the same. Like this:
<asp:TextBox ID="ServerAndClientId" runat="server" ClientIDMode="Static" />
The ID of the label is not "lblError". The ASP.net engine changed the ID. Check the HTML source code in the browser to find out the real ID.
That's not HTML for the label, that is an ASP.NET Control which will be rendered into HTML before it is sent in the response. ASP.NET WebForms controls sometimes change the id for the HTML they create.
View the source of the webpage to see what the id for the HTML element is on the rendered page.
You can use this:
document.getElementById('<%= lblError.ClientID %>').click()
Starting from ASP.NET 4.0 you can use ClientIDMode property for you element. And if you set it into Static then the ClientID value will be set to the value of the ID property:
<asp:Label ID="lblError" runat="server" ClientIDMode="Static" />
will be rendered as something like this:
<span id="lblError" name="ctl00$MasterPageBody$ctl00$Label1" />

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