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" />
Related
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");
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.
I have a UserControl (with FileUpload) included on a Master Page as follows:
Master Page
<uc:uploadFiles ID="UC1" runat="server"/>
uploadFiles.ascx
<script type="text/javascript">
function ValidateUpload() {
var FileUpload_function = document.getElementById('myfile');
if (FileUpload_function.value == '') {
return false;
}
else {
//do stuff }
return true;
}
</script>
<div id="div_FileUpload" class="FileUpload_content" runat="server">
<asp:FileUpload ID="myfile" class="FileUpload" runat="server" />
<asp:CustomValidator ID="CustomValidator1" runat="server" ControlToValidate="myfile" ClientValidationFunction="ValidateUpload" />
</div>
When I run the page I get the following error caused by the CustomValidator:
Unable to get property 'value' of undefined or null reference.
My guess is that the FileUpload value is validated before the entire page is rendered because when I delete the UserControl and move the codes to the MasterPage directly, the CustomValidator works fine.
How can I solve the problem?
You need to use .ClientID in document.getElementById. Becasue when you use that in user control, cotnrol id - myfile might be renamed to something else, like ct00_myfile and in that case if you execute same js code, it will give you null.
You need to use following js code.
var FileUpload_function = document.getElementById('<%=myfile.ClientID %>');
How can I make a <asp:Panel> visible using javascript?
I have done the following but get an error (Cannot Read property style of null)
<asp:Panel runat="server" id="panNonAfricanCountries" Visible="false">
var panNonAfricaDropDown = document.getElementById("panNonAfricanCountries")
if (dropDownFirst == "Yes") {
panNonAfricaDropDown.style.visibility = "visible";
}
The Visible="false" on an asp.net control have as result to not render the control on the page.
What you try to do here is to render it, but with css style to have it hidden from the user until using javascript show it. To archive that do not use the Visible, but set a style or a css to your Panel.
<asp:Panel ID="PanelId" runat="server" Visible="true" style="visibility:hidden" >
Some Content here...
</asp:Panel>
The asp.Panel is render as div and your html on the page will probably as:
<div id="PanelId" style="visibility:hidden">
Some Content here...
</div>
and I say probably because we do not know for sure how the Id is rendered. To get it we use the PanelId.ClientID and your final javascript code will be:
var panNonAfricaDropDown = document.getElementById("<%=PanelId.ClientID%>");
if (dropDownFirst == "Yes" && panNonAfricaDropDown) {
panNonAfricaDropDown.style.visibility = "visible";
}
ASP.NET mangles the names of elements that run on the server. You will have to find the mangled name and then do document.getElementById on that name.
Alternatively, you can use the ClientIDMode property of asp:panel to turn off the mangling (http://msdn.microsoft.com/en-us/library/system.web.ui.control.clientidmode.aspx)
I'm using the javascript below to read the value of an asp.net control in the client-side. However, it always returns the null value. I'm using similar code at other pages in my website, but now i can't read this specific control. Please suggest anyways I can fix this problem.
<asp:Label ID="srch_data" runat="server" ClientIDMode="Static" ></asp:Label>
var srch_data = document.getElementById("<%= srch_data.ClientID %>");
alert(srch_data);
Try using single quotes:
var srch_data = document.getElementById('<%= srch_data.ClientID %>').value;
Try this
var srch_data =document.getElementById('srch_data').innerHTML;
ASP.Net Label becomes span after rendering so instead of finding a label which can not be recognized by JS better find
Add the defer attribute to your script element. I tested and it worked.
Try something like below -
<%--defer indicates the script to be run after the document is completely parsed.--%>
<script type="text/javascript" language="javascript" defer="true">
var label = document.getElementById("<%= srch_data.ClientID %>");
alert("label : " + label);
</script>
<asp:Label ID="srch_data" runat="server" ClientIDMode="Static"></asp:Label>
This should fix your issue.