asp.net repeater - the server tag is not well formed

Hi Experts,

I am using an asp.net repeater and am trying to assign an id to a checkbox and a button at the time the data is loaded into the repeated item,

the code I am using for the checkbox at the moment is

<asp:CheckBox runat="server" ID='<%# Eval("ContactId") %>' />

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the error I am getting is as per the title

the server tag is not well formed

however looking around there is a lot of this issue, but with the onclientclick event and none of the solutions I have found have worked which is why I am asking here.

if anyone has a way around this I would be extremely grateful for your help.