[c#] ASP.NET set hiddenfield a value in Javascript

I don't know how to set the value of a hiddenField in Javascript. Can somebody show me how to do this?

Javascript:

document.getElementById('hdntxtbxTaksit').value = "";

HTML:

<asp:HiddenField ID="hdntxtbxTaksit" runat="server" Value="" Visible="false">   </asp:HiddenField>

error : "Unable to get value of the property \'value\': object is null or undefined"

asp:HiddenField as:

<asp:HiddenField runat="server" ID="hfProduct" ClientIDMode="Static" />

js code:

$("#hfProduct").val("test")

and the code behind:

hfProduct.Value.ToString();

I will suggest you to use ClientID of HiddenField. first Register its client Id in any Javascript Variable from codebehind, then use it in clientside script. as:

.cs file code:

ClientScript.RegisterStartupScript(this.GetType(), "clientids", "var hdntxtbxTaksit=" + hdntxtbxTaksit.ClientID, true);

and then use following code in JS:

document.getElementById(hdntxtbxTaksit).value= ""; 

My understanding is if you set controls.Visible = false during initial page load, it doesn't get rendered in the client response. My suggestion to solve your problem is

Don't use placeholder, judging from the scenario, you don't really need a placeholder, unless you need to dynamically add controls on the server side. Use div, without runat=server. You can always controls the visiblity of that div using css. If you need to add controls dynamically later, use placeholder, but don't set visible = false. Placeholder won't have any display anyway, Set the visibility of that placeholder using css. Here's how to do it programmactically :

placeholderId.Attributes["style"] = "display:none";

Anyway, as other have stated, your problems occurs because once you set control.visible = false, it doesn't get rendered in the client response.

I suspect you need to use ClientID rather than the literal ID string in your JavaScript code, since you've marked the field as runat="server".

E.g., if your JavaScript code is in an aspx file (not a separate JavaScript file):

var val = document.getElementById('<%=hdntxtbxTaksit.ClientID%>').value;

If it's in a separate JavaScript file that isn't rendered by the ASP.Net stuff, you'll have to find it another way, such as by class.

document.getElementById('<%=hdntxtbxTaksit.ClientID%>').value

The id you set in server is the server id which is different from client id.

Try setting Javascript value as in document.getElementByName('hdntxtbxTaksit').value = '0';

• First you need to create the Hidden Field properly

  <asp:HiddenField ID="hdntxtbxTaksit" runat="server"></asp:HiddenField>

• Then you need to set value to the hidden field

  If you aren't using Jquery you should use it:

  document.getElementById("<%= hdntxtbxTaksit.ClientID %>").value = "test";

  If you are using Jquery, this is how it should be:

  $("#<%= hdntxtbxTaksit.ClientID %>").val("test");

try this code:

$('hdntxtbxTaksit').val('test');