.NET developer: Web API

Sefism..NET developer: Web API

Tauseef Fayyaz

A to Z

Glossary

Every concept in this sheet, plus the smaller terms it uses. Select a concept to open its card.

C

Choosing a collection: List<T> keeps order and allows duplicates.
Collection expressions: Since C# 12, [a, b, c] creates an array, List, Span or other collection, chosen by the target type.

D

Deferred execution: A LINQ query does nothing when you write it.

E

Exceptions, using and finally: Code throws an exception for a situation it cannot handle; the nearest matching catch up the call stack handles it.
Extension methods and extension members: An extension method adds a method to a type you do not own, through a static class and a this parameter.

F

First, Single and the OrDefault versions: First takes the first match and throws if there is none.

G

Generics and constraints: Generics let a class or method work with any type while staying type-safe: List<Order> only holds orders.
GroupBy and aggregates: GroupBy buckets items by a key; Sum, Count, Average, Min and Max reduce a sequence or each group to one value.

I

IEnumerable vs IQueryable: IEnumerable runs LINQ in memory with C# delegates.

N

Nullable reference types: With <Nullable>enable</Nullable> (on in every new template) string means never null and string? means may be null.

P

Pattern matching and switch expressions: Patterns test the shape of a value: its type, a constant, a range or its properties.
Primary constructors: Since C# 12, a class can declare constructor parameters next to its name.

R

Records: A record is a type built for data: the compiler writes value equality, a readable ToString and, with positional syntax, an immutable constructor and properties.

V

Value types and reference types: A struct (int, decimal, DateTime, your own structs) is copied when you assign or pass it.

W

Where, Select and OrderBy: LINQ methods chain together: Where filters, Select shapes each item into something new, OrderBy and ThenBy sort, Take and Skip page.