What is struct in C#?
A struct type is a value type that is typically used to encapsulate small groups of related variables. When an object is created from a struct and assigned to a variable, the variable contains the complete value of the struct. When a variable that contains a struct is copied, all the data is copied, and any modification to the new copy does not change the data for the old copy. Because structs do not use references, they do not have identity; you cannot distinguish between two instances of a value type with the same data.
Structs can also contain constructors, constants, fields, methods, properties, indexers, operators, events, and nested types.
Structs have the following properties:
- Structs are value types.
- Unlike classes, structs can be instantiated without using a new operator.
- Structs can declare constructors, but they must take parameters.
- A struct cannot inherit from another struct or class, and it cannot be the base of a class. All structs inherit directly from System.ValueType, which inherits from System.Object.
- A struct can implement interfaces.
- A struct can be used as a nullable type and can be assigned a null value.
What are the limitations of struct in comparison to classes?
- Within a struct declaration, fields cannot be initialized unless they are declared as const or static.
- A struct may not declare a default constructor (a constructor without parameters) or a destructor.
- Structs can implement an interface but they cannot inherit from another struct. For that reason, struct members cannot be declared as protected.
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Why a struct does not declare a default constructor?
Because copies of structs are created and destroyed automatically by the compiler, a default constructor and destructor are unnecessary. In effect, the compiler implements the default constructor by assigning all the fields of their default values.
Explain similarities between class and struct?
Structures and classes are similar in the following respects:
- Both are container types, meaning that they contain other types as members.
- Both have members, which can include constructors, methods, properties, fields, constants, enumerations, events, and event handlers. However, do not confuse these members with the declared elements of a structure.
- Members of both can have individualized access levels. For example, one member can be declared Public and another Private.
- Both can implement interfaces.
- Both can have shared constructors, with or without parameters.
- Both can expose a default property, provided that property takes at least one parameter.
- Both can declare and raise events, and both can declare delegates.
What are the differences between class and struct?
When to choose struct instead of class?
Classes are reference types and structures are value types. Reference types are allocated on the heap, and memory management is handled by the garbage collector. Value types are allocated on the stack or inline and are deallocated when they go out of scope. In general, value types are cheaper to allocate and deallocate.
Consider defining a structure instead of a class if instances of the type are small and commonly short-lived or are commonly embedded in other objects.
Do not define a structure unless the type has all of the following characteristics:
- It logically represents a single value, similar to primitive types (integer, double, and so on).
- It has an instance size smaller than 16 bytes.
- It is immutable.
- It will not have to be boxed frequently.
If one or more of these conditions are not met, create a reference type instead of a structure. Failure to adhere to this guideline can negatively impact performance.
What is the base type from which all structs inherit directly?
All structs inherit directly from System.ValueType, which inherits from System.Object.
Can a struct have a default constructor (a constructor without parameters) or a destructor in C#?
Can you instantiate a struct without using a new operator in C#?
Yes, you can instantiate a struct without using a new operator
Can a struct inherit from another struct or class in C#?
No, a struct cannot inherit from another struct or class, and it cannot be the base of a class.
Can a struct implement an interface in C#?
Classes and structs support inheritance. Is this statement true or false?
False, Only classes support inheritance. structs do not support inheritance.
Classes and structs can be declared as static, Is this statement true or false?
False, only classes can be declared as static and not structs.
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