Hope this helps.

Great post Colin. I think interfaces can sometimes be hard to wrap your mind around. Once a person has that “aha” moment, they will never turn back.

SIDE NOTE: The only thing a degree in our field, unfortunately, will do is get your foot in the door for an interview (usually). If you have a recruiter who actually reads the resumes and sees the the experience listed, everyone has a fighting chance.

I personally don’t rate a developer on his education. I base it on experience.

Jamal: I think your example is pretty much why C# disallows multiple inheritance. Imagine what sort of a mess you could get in then!

I am on the same path Colin. I have no degree, kind of stumbled into programming from web development and learned as I went, no mentor just myself reading books and asking for help in groups. As a result it took me awhile to fully leverage the power of interfaces. After using them for awhile now I don’t see how I got on without them.

The best piece advice I can give everyone to help them with interfaces is first, the word “Contract”. It confused me alot at first but it made sense later because all the interface does is assure clients that said class can perform the interface operations.

Then to the next step of once you know that a class can do a certain set of methods, you can then swap out classes that otherwise have no relation to each other. If they did, you could use inheritance.

A prime example I just coded the other night. I had an interface called IAuthService. The interface has two methods:

bool Authenticate(string username, string password);
string[] GetGroupMembership(string username);

Now, there are two classes that implement this interface,
ActiveDirectoryAuthService : IAuthService
DatabaseAuthService : IAuthService

The consumer method would then be like so:
class Consumer
{
public void DoWork(IAuthService myAuthService)
{
return myAuthService.Authenticate(“un”, “pw”);
}
}

As you can see, I can now change the classes the consumer is using very easily, because the consumer doesn’t care how the task is achieved, it just wants the task to be done.

Therein lies the power, loose coupling. Because no consumer knows about the intimate details of the AuthService class. Only how to interact with it.

Hopefully thats not too confusing. An example like that really helped me to see the light with interfaces when I first started using them.

Didn’t mean to hijack your thread colin, just wanted to let everyone know what helped me see the light.

good post colin!