Summary: in this tutorial, you’ll learn about expression-bodied members to make your code concise and more readable.
Introduction to expression-bodied members
C# introduced the expression body definition for methods and read-only properties in version 6 and expanded it to properties, constructors, finalizers, and indexers in version 7.
An expression body definition has the following syntax:
member => expression;
Code language: C# (cs)
In this syntax:
- The
member
can be a method, a property, a constructor, a finalizer, or an indexer. - The
expression
is any valid expression.
The purpose of the expression body definition is to make the code concise and more readable.
Methods
If a method has a single expression that returns a value whose type matches the method’s return type, you can use an expression body definition.
For example, the following example defines the Person
class:
// Person.cs class Person { public string FirstName { get; set; } public string LastName { get; set; } public byte Age { get; set; } public string GetFullName() { return $"{FirstName} {LastName}"; } }
Code language: C# (cs)
In this Person
class, the GetFullName()
method returns a string that matches the return type of the method:
public string GetFullName() { return $"{FirstName} {LastName}"; }
Code language: C# (cs)
Therefore, you can use an expression-bodied method as follows:
public string GetFullName() => $"{FirstName} {LastName}";
Code language: C# (cs)
And here’s the new Person
class:
// Person.cs class Person { public string FirstName { get; set; } public string LastName { get; set; } public byte Age { get; set; } public string GetFullName() => $"{FirstName} {LastName}"; }
Code language: C# (cs)
Read-only properties
Starting with C# 6, you can use expression body definition for a read-only property. For example, the following adds the CanVote
read-only property to the Person
class:
// Person.cs class Person { public string FirstName { get; set; } public string LastName { get; set; } public byte Age { get; set; } public bool CanVote { get { return Age >= 16 && Age <= 65; } } public string GetFullName() => $"{FirstName} {LastName}"; }
Code language: C# (cs)
Since the CanVote
property is read-only, you can use an expression body definition like this:
public bool CanVote => Age >= 16 && Age <= 65;
Code language: C# (cs)
Here’s the updated Person
class:
// Person.cs class Person { public string FirstName { get; set; } public string LastName { get; set; } public byte Age { get; set; } public bool CanVote => Age >= 16 && Age <= 65; public string GetFullName() => $"{FirstName} {LastName}"; }
Code language: C# (cs)
Constructors
The following example defines the Skill
class whose constructor has an expression that assigns the skill name to the Name
property:
class Skill { public string Name { get; set; } public Skill(string name) { Name = name; } }
Code language: C# (cs)
Hence, you can use the expression body definition for the Skill constructor as follows:
class Skill { public string Name { get; set; } public Skill(string name) => Name = name; }
Code language: C# (cs)
Indexers
The following example defines the Matrix class that uses an index to access an element at a row and column:
// Matrix.cs class Matrix { private double[,] data; public Matrix(int row, int column) { data = new double[row, column]; } public double this[int row, int column] { get { return data[row, column]; } set { data[row, column] = value; } } }
Code language: C# (cs)
In this example, the get
and set
accessors of the indexer have only one expression. So you can use an expression body definition as follows:
// Matrix.cs class Matrix { private double[,] data; public Matrix(int row, int column) => data = new double[row, column]; public double this[int row, int column] { get => data[row, column]; set => data[row, column] = value; } }
Code language: C# (cs)
Summary
- Use the C# expression-bodied members to make the code concise and more readable.