User Defined Types

User-Defined Type

A custom data type created by a programmer to represent information and behavior specific to an application.

Structure (struct)

a user-defined value type that groups related data together. Unlike classes, these are stored by value and are typically used for small, lightweight objects.

Interface

Defines a contract that specifies which members a class or structure must implement without providing their implementation

Enumeration (enum)

a user-defined value type that represents a fixed set of named constants

enum ElementState { Solid, Liquid, Gas }

Type an example of ‘enum’

Record

A reference type designed primarily for storing immutable data. They automatically provide value-based equality and simplified syntax

Record Struct

A value type that combines the lightweight storage of a structure with the value-based equality features of a record.

Delegate

A type-safe object that stores a reference to one or more methods, allowing methods to be passed as arguments or called indirectly

Event

A mechanism that allows one object to notify other objects when a specific action or change has occurred.

Generic Type

A class, structure, interface, or method that uses type parameters so it can operate on different data types while maintaining type safety.

Type Parameter

A placeholder for a data type used when defining a generic type or generic method.

Generic Constraint

Restricts the kinds of data types that can be used as type arguments for a generic type or method.

Partial Class

Allows the definition of a single class to be split across multiple source files

Nested Type

A class, structure, interface, or enumeration declared inside another type.

Anonymous Type

A compiler-generated type whose name is not explicitly declared by the programmer. It is commonly used for temporary objects

Nullable Value Type

Allows a value type to also store the value ‘null’

int? double? bool?

Type three examples of nullable value types

Nullable Reference Type

Reference type that explicitly indicates that a reference variable is allowed to contain ‘null’, improving compile-time null-safety

Type Alias

Assigns an alternate name to an existing type using the ‘using’ directive

using Atom = Chemistry.Element

Type an example of ‘Type Alias’

Accessibility Level

Determines where a user-defined type can be accessed within a program

public internal private

Type three examples of Accessibility levels

Sealed Class

A class that cannot be inherited by another class

Abstract Class

A class that cannot be instantiated directly and is intended to serve as a base class for other classes.