Day 01 Generics and Extension Methods

Day 01 - Generics, Extension Methods


Fun With Generics	Touching the hard points of .net Generics: Constraints, Covariance and Inference

The purpose of Generics
About Boxing and Unboxing
Static members of Generic classes
Generic Constraints
- How to create base class constraint
- How to create interface constraint
- How to create value type / reference type constraint
- How to create default constructor constraint
Generic Inference
Generic Invariance, Covariance and Contravariance

We have created a value type for complex numbers: Complex
We have implemented the IComparable<Complex> and IComparer<Complex> interfaces to allow a "natural" and "alternative" orders
We have implemeneted IEquatable<Complex> to allow it to compare itself to other Complex instances
We discussed the Equals that we derive from object and how to override it
- Always override the Equals method from object (the compiler warns if you do not)
- Always override the GetHashCode method too (the compiler warns if you do not) - this is important to allow the object to be used as key in HashSets

We have discussed the various types of collections that we have in .net and what they are specifically good for
- List<T> - Ordered collection that allows Fast random access by index (O(1)), avarage modification (o(1), O(N)), and slow find operations (O(N))
- Dictionary<K, T> - Store items by keys instead of indices. random access by key: O(1) (or very close to, depends on hashing algorithm) Add and remove like List. Find operations are O(1) by key and O(N) by value
- HashSet<T> - Very fast access, modifications, and find, but do not support order (no notion of index).
- We have also discussed SortedSet, SortedList, SortedDictionary, Stack and Queue briefly

We created a static class and a static method inside it
We have seen how to add a new invokation syntax by adding the keyword this to the first parameter of the method
By using extension methods, we saw that we can create Fluent APIs which are much more readable