Please post code in a code block, it is virtually unreadable like this! You can do that by clicking the code block link at the top of the editor or by surrounding the code with <pre> and </pre>.
If you just want to turn of the error... disable EventValidation (just like the error message reads). I don't know if that really solves your problem (or just shuts off a symptom).
Just change your Page directive
<%@Page EnableEventValidation="false" ...%>
Please be aware, that this might introtduce a big security risk!