« Record » : différence entre les versions
De Banane Atomic
Aller à la navigationAller à la recherche
| Ligne 52 : | Ligne 52 : | ||
= [https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/record#value-equality Value equality] = | = [https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/builtin-types/record#value-equality Value equality] = | ||
Two record objects are equal if they are of the same type and store the same values. | Two record objects are equal if they are of the same type and store the same values. | ||
<kode lang='cs'> | |||
public record Person(string Name, string[] PhoneNumbers); | |||
var phoneNumbers = new string[1] { "06-10-20-30-40" }; | |||
Person person1 = new("Nicolas", phoneNumbers); | |||
Person person2 = new("Audrey", phoneNumbers); | |||
Console.WriteLine(person1 == person2); // True | |||
person1.PhoneNumbers[0] = "06-11-22-33-44"; | |||
Console.WriteLine(person1 == person2); // True | |||
</kode> | |||
Version du 9 août 2024 à 13:48
Links
Definition
Built-in functionality for encapsulating immutable data.
C# 10 allows the record class syntax as a synonym to clarify a reference type, and record struct to define a value type.
Primary constructor
When you declare a primary constructor on a record, the compiler generates public properties for the primary constructor parameters.
|
public record Person(string FirstName, string LastName);
// with the generated properties it is equivalent to
public record Person
{
public required string FirstName { get; init; }
public required string LastName { get; init; }
};
// record struct value type with immutable properties
public readonly record struct Point(double X, double Y);
// equivalent to
public record struct Point
{
public double X { get; init; }
public double Y { get; init; }
}
// record struct value type with mutable properties
public record struct Point(double X, double Y);
// equivalent to
public record struct Point
{
public double X { get; set; }
public double Y { get; set; }
}
|
Immutability
Immutability means the data of the record don't change after its creation.
It is useful when you need thread-safe data-centric types or expect hash codes remaining the sames.
However, the data that a reference-type property refers to can be changed:
|
|
public record Person(string Name, string[] PhoneNumbers);
Person person = new("Nicolas", new string[1] { "06-10-20-30-40" });
// the PhoneNumbers array is immutable, but the string in the array are mutable
person.PhoneNumbers[0] = "06-11-22-33-44";
|
Value equality
Two record objects are equal if they are of the same type and store the same values.
|
|
public record Person(string Name, string[] PhoneNumbers);
var phoneNumbers = new string[1] { "06-10-20-30-40" };
Person person1 = new("Nicolas", phoneNumbers);
Person person2 = new("Audrey", phoneNumbers);
Console.WriteLine(person1 == person2); // True
person1.PhoneNumbers[0] = "06-11-22-33-44";
Console.WriteLine(person1 == person2); // True
|
