Textbox.text empty in codebehind after assigning .value from javascript

[thetodaisies]

Hi,
I have an aspx textbox control in my webpage its value is being assigned from javascript. Now once the value is assigned from javascript it returns empty string when tried Textbox.text from c#
codebehind on submit.

here is the definition of the textbox
<asp:TextBox ID="TxtTags" CssClass="TextBoxStyle" runat="server" ReadOnly ="true" onclick="javascript:ToggleDropDown()"></asp:TextBox>

on focus of this textbox it shows a list of values and on selection of it the selected values are assigned to the text

in javascript:

document.getElementById("TxtImpactTags").value = selectedStr;

Thanks for any help

[thetodaisies]

the issue i think was the textbox was readonly. when readonly attribute was removed i can get the text in codebehind