How to assign an expression to a method in C#6

In this post we saw how to assign expressions to class properties in C# 6 using the lambda operator “=>”:

public string FullName => string.Format("{0} {1}", FirstName, LastName);

This property getter was part of a Person class:

public class Person
{
	public int Age { get; }
	public string FirstName { get;}
	public string LastName { get; }
        public string FullName => string.Format("{0} {1}", FirstName, LastName);

	public Person(string firstName, string lastName, int age)
	{
		FirstName = firstName;
		LastName = lastName;
		Age = age;
	}
}

The same type of syntax exists for one-liner functions. It’s really just syntactic sugar which saves you a return statement and the brackets.

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How to assign an expression to a class property in C#6

Consider the following Person class written using the new immutable property syntax of C# 6:

public class Person
{
	public int Age { get; }
	public string FirstName { get;}
	public string LastName { get; }

	public Person(string firstName, string lastName, int age)
	{
		FirstName = firstName;
		LastName = lastName;
		Age = age;
	}
}

Then let’s say you’d like to add a new property that returns the full name of the person. In C# 5 you’d write something like this:

public string FullName
{
	get
	{
		return string.Format("{0} {1}", FirstName, LastName);
	}
}

Note that the “get” body is very simple, it’s only one line.

In C# 6 we can assign expressions to properties using the familiar “=>” operator as follows:

public string FullName => string.Format("{0} {1}", FirstName, LastName);

How neat is that? You can call this property on the Person object as you would in any other case:

Person p = new Person("John", "Smith", 28);
Console.WriteLine(p.FullName);

…which prints John Smith as expected.

Let’s add one more example. We’ll add an Old property with a simple logic. Anyone over and above the age of 35 will be old. That includes me as well, don’t worry:

public bool Old => Age > 35;

Calling p.Old on the above example will return false.

View all various C# language feature related posts here.