solution to make a open source web application in asp.net limited to be redistributed

we have implemented a web application in asp.net 4.0 and customer needs us to give them the source code too so they can do the maintenance and limited improvements of application themselves ,but we need to make sure that they can not change the application(e.g interface) and sell that to other customers,what is the solution?

p.s: actually we need to make sure that only they can use that web application,not anybody else.

Re: solution to make a open source web application in asp.net limited to be redistributed

Ok, there are many questions in here.

Regarding not being able to modify the interface, that's a tricky one. Most sites have their business logic compiled and forms as "editable" aspx files. In order to compile pages you need to use web application project instead of website.

Then in order to protect your app there are 2 levels of protection:

1. Protecting from unwanted ejecution: you need to implement some sort of licensing mechanism. Apps at my company have a built in licensing method that generates licenses PER SERVER so licenses cannot be shared between copies of the app

2. Protecting against code inspection (decompilation): None of above will be of any use unless you OBFUSCATE your code. That will gave you some level of protection against customers (or whatever) trying to see how's your stuff programmed. Remember .net assemblies are compiled into intermediate language and can be decompiled to 100% functional code. Try ".net reflector" and see for yourself

finally, this is not a simple matter. After years on the field, we're still changing stuff in our licencing/protection mechanisms not and then