asp.net, html control

<div id="collapseTwo" class="accordion-body collapse">
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox9" SetFocusOnError="true" ForeColor="Red" ErrorMessage="*"></asp:RequiredFieldValidator>
           
<br /><asp:TextBox runat="server" ID="TextBox9"></asp:TextBox>
</div>

<asp:Button runat="server" ID="finalize" Text="Finalize all information" CssClass="btn btn-primary arrow-right" onclick="finalize_Click" />

if the button is on click, I want to switch as follow (basically just switch css class name to 'accordion-body collapse in'

<div id="collapseTwo" class="accordion-body collapse in">
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox9" SetFocusOnError="true" ForeColor="Red" ErrorMessage="*"></asp:RequiredFieldValidator>
           
<br /><asp:TextBox runat="server" ID="TextBox9"></asp:TextBox>
</div>
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Aaron JabamaniTechnical ArchitectCommented:
add this, to the server button,  OnClientClick="return call()"  . In the call javascript, use query to change the class value. Make sure you return true  in the call javascript method, so that  a post back happens.
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