How to set a C# variable value from javascript

Question

I'm making an ajax request and storing my response in an hidden field.I'm doing this through javascript using getelementbyid.value.This javascript function is on body onload.Now after I get this value I would like to use this in C#.I can't have any button onclick event or anything of that sort.Just have a hidden input type

As per my understanding u cant use script variable on server side. Also can u put some piece of code here? — Amit Soni
– Amit Soni, Commented Nov 12, 2010 at 5:27

Abe Miessler · Accepted Answer · 2010-11-12 05:42:03Z

5

If an asp.net HidenField webControl has a value then all you need to do is the following:

aspx page:

        <asp:hiddenfield id="hf_MyValue"
          value="whatever" 
          runat="server"/>

cs page:

string value = hf_MyValue.Value;

If you want to do something with the value when it's assigned handle the onValueChanged event:

        <asp:hiddenfield id="hf_MyValue"
          onvaluechanged="ValueHiddenField_ValueChanged"
          value="whatever" 
          runat="server"/>

While you CAN use a value of an asp.net HiddenField that is set using javascript in C# make sure that you understand that this can only be done after a postback.

Here is some info on the Client/Server relationship. Javascript and C# respectively in your question.

edited Nov 12, 2010 at 5:42

answered Nov 12, 2010 at 5:35

Abe Miessler

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1 Comment

gizgok Over a year ago

Can you tell me how to postback for hidden field.I tried and it's not working

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