Custom code access permissions

Question

We have a server written in C# (Framework 3.5 SP1). Customers write client applications using our server API. Recently, we created several levels of license schemes like Basic, Intermediate and All. If you have Basic license then you can call few methods on our API. Similarly if you have Intermediate you get some extra methods to call and if you have All then you can call all the methods.

When server starts it gets the license type. Now in each method I have to check the type of license and decide whether to proceed further with the function or return.

For example, a method InterMediateMethod() can only be used by Intermediate License and All license. So I have to something like this.

public void InterMediateMethod()
{
   if(licenseType == "Basic")
    {
         throw new Exception("Access denied");
    }
}

It looks like to me that it is very lame approach. Is there any better way to do this? Is there any declarative way to do this by defining some custom attributes? I looked at creating a custom CodeAccessSecurityAttribute but did not get a good success.

Answer 1

Since you are adding the "if" logic in every method (and god knows what else), you might find it easier to use PostSharp (AOP framework) to achieve the same, but personally, I don't like either of the approaches...

I think it would be much cleaner if you'd maintained three different branches (source code) for each license, which may add a little bit of overhead in terms of maintenance (maybe not), but at least keep it clean and simple.

I'm also interested what others have to say about it.

Good post, I like it...