Most important things about C# generics… lesson learned [closed]

Answer 1

I've learnt that generics is indeep powerful tool yet misused leads to very unreadable code.

Answer 2

Don't know if they are most important, but I've learned the following:

Generics will only be instantiable via reflection if you don't know the frikkin type. In some cases you may need non-generic interfaces to use your generic classes in situations where the type is unknown.

I almost wrecked my head until I grocked that

public class Foo<T> where T : Foo<T> {
  public T CloneMe() ...
}

is perfectly valid code and allows your base class to expose methods and properties related to the specialized class...that ended up in a definition of a state machine along its states:

public abstract class Machine<S,M> where S : State<S,M> where M : Machine<S,M>  {
    protected S state;
}

public abstract class State<S,M> where S : State<S,M> where M : Machine<S,M> {
    protected M machine;
}

Generics can get a bit unwieldy. The other day I had this:

List<Tuple<Expression<Func<DataTable,object>>,Expression<Func<DataTable,object>>>>

phew...

Answer 3

No covariance or contra-variance (at least in 3.5). Be aware of this when designing class hierarchies that include generic type parameters.

Answer 4

First of all it is inportant to know how Generics work in C#. This article gives you a good overview of generics by Anders Hejlsberg (The father of c#). I don't think that using them as often as possible is that good. Use generics when they really make sense. Always remember KISS and YAGNI (Keep It Simple Stupid; You Ain't Gonna Need It) from extreme programming.

Answer 5

One of the most important things I've learned is that you can constrain the generic type parameter(s). This can be very powerful, allowing you to take customize the class for only certain types of objects and allowing you to use the members of that type in your generic class. I realize that this is pretty fundamental, but it's one of the things that makes generics incredibly useful.