Disable ActionLink in MVC

Question

Hi,
In MVC application I need to disable actionlink when user enter "known" in textbox. How to do it?
if( textbox value == "known")  then
disable actionlink 
 
I am trying to do in Jquery also but its not working

if (item.name == "Unknown") {

            $("#lnkCompare").hide();

        }

Thank you,