C# Records Vs Class: A Comprehensive Comparison

C# Records vs Class: Introduction and Basics

When it comes to creating data structures in C#, developers have traditionally relied on classes. However, with the release of C# 9.0, a new feature called records has been introduced, offering an alternative way of defining immutable data structures. In this article, we will explore the key differences between records and classes, and discuss when it is appropriate to use one over the other.

Immutable Data Structures

One of the fundamental differences between records and classes is that records are immutable by default. This means that once a record is created, its values cannot be changed. In contrast, classes are mutable and allow for modification of their state.

The immutability of records provides several benefits. First, it ensures that the state of the record remains consistent throughout its lifetime, making it easier to reason about the behavior of the code. Second, immutability allows records to be safely shared across multiple threads in concurrent applications without the need for locks or other synchronization mechanisms.

To create a record in C#, you simply use the `record` keyword followed by the name of the record and its properties:

“`csharp
public record Person(string Name, int Age);
“`

In this example, we have defined a record called `Person` with two properties: `Name` of type string and `Age` of type int. Once created, a record can be instantiated just like a class:

“`csharp
var person = new Person(“John Doe”, 30);
“`

Structural Equality and Value-Based Equality

Another key feature of records is that they automatically provide structural equality based on their properties. This means that two records are considered equal if their properties have the same values, regardless of their references in memory.

For example, consider the following code:

“`csharp
var person1 = new Person(“John Doe”, 30);
var person2 = new Person(“John Doe”, 30);

Console.WriteLine(person1 == person2); // Output: true
“`

In this case, `person1` and `person2` are considered equal because their properties have identical values. This behavior is different from classes, which rely on reference equality by default unless they override the `Equals` and `GetHashCode` methods.

Pattern Matching with Records

Records also provide enhanced pattern matching capabilities compared to classes. With the `is` pattern matching operator, you can easily deconstruct a record into its individual properties:

“`csharp
if (person is Person { Age: 30 })
{
Console.WriteLine(“John Doe is 30 years old.”);
}
“`

In this example, the record `person` is checked if it has an `Age` property with the value of 30. If the condition is met, the corresponding code block is executed.

Inheritance and Polymorphism with Records

While classes support inheritance and polymorphism, records do not allow inheritance by default. This is because records are primarily intended for representing data structures and are not designed to be used as a base for other classes or records.

However, if inheritance is necessary, you can use the `sealed` modifier to prevent further inheritance and explicitly declare the base record’s properties in the derived record:

“`csharp
public record Employee(string Name, int Age) : Person(Name, Age)
{
public string Department { get; init; }
}
“`

In this example, an `Employee` record is derived from the `Person` record, with an additional `Department` property. By using the `: Person(Name, Age)` syntax, we indicate that `Employee` includes all properties from `Person`.

Performance Considerations and Best Practices

When comparing the performance of records and classes, it is important to consider the specific use case and requirements of your application. In general, records can offer better performance in scenarios where immutability is required and frequent copying of objects is involved.

One potential performance advantage of records is that they offer structural equality by default, which means that equality checks can be performed more efficiently. However, if custom equality logic is necessary, it is recommended to override the `Equals` and `GetHashCode` methods explicitly.

Although records provide numerous benefits, it is important to note that they are not intended to replace classes completely. Classes are still the preferred option for objects with mutable state or when complex behavior is required. Records should be used specifically for representing immutable data structures.

Frequently Asked Questions (FAQs)

Q: Can I modify the properties of a record once it is created?
A: No, records are immutable by default, meaning their properties cannot be modified after creation. If you need to modify a property, you can create a new record with the modified values.

Q: When should I use records instead of classes?
A: Records are particularly useful when you need immutable data structures or when you want to take advantage of the built-in structural equality and pattern matching features. Use classes when you require mutable state or complex behaviors.

Q: Can records be used in concurrent applications?
A: Yes, the immutability of records makes them safe to share across multiple threads without the need for locks or other synchronization mechanisms.

Q: Are records supported in older versions of C#?
A: No, records were introduced in C# 9.0 and are not available in older versions of the language.

Q: Can I inherit from a record?
A: By default, records do not support inheritance. However, you can use the `sealed` modifier to prevent further inheritance and explicitly include the base record’s properties in the derived record.

In conclusion, records provide a powerful alternative to classes when creating immutable data structures in C#. With their built-in structural equality, enhanced pattern matching capabilities, and performance benefits, records offer a compelling option for representing and manipulating data. However, it is important to evaluate the specific requirements of your application and determine whether records or classes are the most suitable choice.