Changing textbox value should update hidden field

I have a hidden field which i want to update everytime when my textbox value is changed. It doesnt matter whether i am changing value at server side or client side when the textbox value changes hidden field should be updated. I have used onchange event of textbox but it does not work as i am 开发者_JAVA技巧changing values of textbox programatically. How can i do this?

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You need to do it separately.

In the code behind you need to add in the TextBox_TextChanged event

HiddenField.Value = TextBox.Text

And in the client side you need to add the onchange event like onchange="javascript:updateHiddenField();" and then do something like:

function updateHiddenField() {
  document.getElementById('HiddenFieldClientID').value = document.getElementById('TextBoxClientID').value  
}

Beware that if you use MasterPages or databinding controls like repeaters/gridviews etc then the ClientID won't be the same as the ID.

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A hidden field defined thusly:

<input type="hidden" id="BillMeFormReferred" name="referred" />

needs to pull the value of a textbox that is contained by a different form - that is, the hidden field is on a form being submitted - the text box sits in a different form _not_being_submitted.

jQuery is able to accomplish this via a button coded thusly:

<input type="button" value="Bill Me" id="BillMe"
  onclick="$('#BillMeFormReferred').val(   // the setter form of .val
                   $('#tbReferred').val() //  references the remote field ID
                   ); $('#BillMeForm').submit();" />