C# 7.0 Features

C# language some Keys to know:

1. In C# language to know the which dot net version you are using at run time you can use “Enviourment.Version”.
You can also find;

2. C# 7.0 Features :-
— 1. Touples:-
— 2. Tuple Deconstruction :- Any object can be deconstructed by defining a Deconstruct method in the class:
for example :-
class Person
public string FirstName { get; set; }
public string LastName { get; set; }

public void Deconstruct(out string firstName, out string lastName)
firstName = FirstName;
lastName = LastName;

var person = new Person { FirstName = “John”, LastName = “Smith” };
var (localFirstName, localLastName) = person;

In this case, the (localFirstName, localLastName) = person syntax is invoking Deconstruct on the person.

— An alternative approach for the Person class is to define the Name itself as a Tuple. Consider the following:

Example:- class Person
public (string First, string Last) Name { get; }

public Person((string FirstName, string LastName) name)
Name = name;

Then you can instantiate a person like so (where we can take a tuple as an argument):

var person = new Person((“Jane”, “Smith”));

var firstName = person.Name.First; // “Jane”
var lastName = person.Name.Last; // “Smith”

— Touple Intialization :-

You can also arbitrarily create tuples in code:

var name = (“John”, “Smith”);
// Outputs John

// Outputs Smith

When creating a tuple, you can assign ad-hoc item names to the members of the tuple:

var name = (first: “John”, middle: “Q”, last: “Smith”);
// Outputs John


— 3. Out var declaration

The out var declaration is a simple feature to improve readability. It allows a variable to be declared at the same time that is it passed as an out parameter.

A variable declared this way is scoped to the remainder of the body at the point in which it is declared.

In C# 7.0, you can inline the declaration of the variable passed to the out parameter, eliminating the need for a separate variable declaration:-

Example :-

if (int.TryParse(input, out var value))
Foo(value); // ok
Foo(value); // value is zero

Foo(value); // still ok, the value in scope within the remainder of the body

If some of the parameters that a function returns in out is not needed you can use the discard operator _.

p.GetCoordinates(out var x, out _); // I only care about x

An out var declaration can be used with any existing function which already has out parameters. The function declaration syntax remains the same, and no additional requirements are needed to make the function compatible with an out var declaration. This feature is simply syntactic sugar.

Another feature of out var declaration is that it can be used with anonymous types.
var a = new[] { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
var groupedByMod2 = a.Select(x => new
Source = x,
Mod2 = x % 2
.GroupBy(x => x.Mod2)
.ToDictionary(g => g.Key, g => g.ToArray());
if (groupedByMod2.TryGetValue(1, out var oddElements))

In this code we create a Dictionary with int key and array of anonymous type value. In the previous version of C# it was impossible to use TryGetValue method here since it required you to declare the out variable (which is of anonymous type!). However, with out var we do not need to explicitly specify the type of the out variable.



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