How to pass a string from asp.net code behind to local web storage?

Question

How do i achieve to pass a string from code-behind c# to local storage by using javascript?

I tried to pass the string over an HiddenField and Session cache, but i had no success by retrieving the string in javascript to store it in the local storage. I got an onclick-function in c# to receive a string and write it in the session cache. After that i try to retrieve the string over a function in js where i read the session cache and write it in the local storage. But the result is always empty, except of some tests where i filled the session cache within the page-load function with a static string.

Do anybody suspect the problem in my solution?

I'd appreciate your input.

Edit:

First i push Button "btn1" to write myString into the HF and then "btn2" to read it in JS and storage it in the local storage.

HTML-code

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

<asp:Button ID="btn1" runat="server" OnClick="writeInHiddenField" />
<asp:Button ID="btn2" runat="server" OnClientClick="writeHfInLS()" />

<script>
  function writeHfInLS() { window.localStorage.setItem('key', document.getElementById("hiddenVar").value); }
</script>

C#-function in code behind

writeInHiddenField() { hiddenVar.Value = myString; }

Answer 1

A hidden field will work. Assuming web forms, use an asp:Hidden field:

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

Then, you can retrieve it via:

document.getElementById("LocalStore").value

or JQuery:

$("#LocalStore").val();