ILDASM and Security

Question

hello to all i have a problem with security in .NET i want know how can i protect my program from disassembling by ILDASM tool in vs.net ? i can easily disassemble a asembly and edit IL Code and recompile it by ILASM .. but this is a big problem .. i have read a article that was told we can use from "owner" option in ilasm tool but that option isn't current options and will not be ok .. please a Expert help me .. Thanks alot Farshad