ClipboardJS – using asp.net textbox as target

I have a basic test html page to test using ClipboardJS. It works when the target is html

<input type="text" id="bar" value="Click to copy me" />

<button class="btn" id="btnCopyToClipboard"
        data-clipboard-action="copy"
        data-clipboard-target="#bar"
        onclick="return false">Copy Me</button>

However, I need to use an asp.net textbox as in:

<asp:TextBox ID="txtResponse" class="form-control ans_box_inner" TextMode="MultiLine" runat="server" Rows="20"></asp:TextBox>

and my “button” is defined using ClientID method:

<button id="btnCopyToClipboard" class="btn" 
data-clipboard-action="copy" data-clipboard-target="#<%= txtResponse.ClientID %>'" 
onclick="return false;">
<img src="Images/CopyToClipboardSmall.png" alt="Copy to clipboard" /></button>

And this is not working.