C# - Top 10 New Features (Part 3 of 4)

Article Overview

Background
Pre-requisites
Using Declarations

Points
Example

Nullable Reference Types

Points
Example

Readonly Struct Members

Points
Example

Summary

Background

I have divided this whole article into 4 parts to make it easy to understand. This article mainly focuses on three key features and enhancements to C# 8.0,

Using Declarations
Nullable Reference Types
Readonly Struct Members

Here, I have kept all the implementation details with a complete example.

Prerequisites

You should have a basic knowledge of C#.
In Part 1 of 4; I had explained “How to compile/test with C# 8.0 in MS Visual Studio OR online”, “Key features and enhancements to the C# 8.0”, and the “Switch Expression” feature.
In Part 2 of 4; I had explained key three "Indices and Ranges", "Default Interface Members", and "Static Local Functions" feature.
So, it will be good if you read the first part, i.e., “C# - Top 10 New Features (Part 1 Of 4)” of this article.
So, it will be good if you read the second part, i.e. “C# - Top 10 New Features (Part 2 Of 4)” of this article.

For your reference, I have kept all the examples in a single .cs file and uploaded with this article for your ease of use.

Using Declarations

Below are the key syntax improvements:

Using declaration is a variable declaration preceded by using keyword.
It tells the compiler that a variable being declared should be disposed at end of enclosing scope.
Compiler will generate the call to Dispose() when a variable falls out of scope.
This will be especially useful when multiple instances of types implementing the IDisposable interface are used in same code block.
It enhances the ‘using’ operator to use with patterns and it also makes it more natural.

Now, let us understand it by example.

Example

//Before 8.0
using(var fileStream = new FileStream("abcd.txt",FileMode.Open))
{
//do somthing here
}// fileStream dispose here

//With 8.0
var fileName = "abcd.txt";
if(fileName != null)
{
using var fileStream = new FileStream(fileName, FileMode.Open);
//do somthing here
}// fileStream dispose here

This is very usful when you have multiple using requirements.

Nullable Reference Types

Below are the key syntax improvements,

Nullable reference types will not be checked to ensure that they are not assigned or initialized to null.
Compiler uses the flow analysis to ensure that any nullable reference type variable is checked against null before it is accessed/assigned to a non-nullable reference type.
Key purpose is to allow variable type definitions to specify whether they will have null value assigned to them or not.
It will emit the compiler warning/error if the variable which must not be null is assigned to null.

Now, let us understand by example.

Example

string? nullableString = null;
Console.WriteLine(nullableString.Length);
// WARNING: may be null! So, take care.

Readonly Struct Members

Below are the key syntax improvements,

Readonly modifier can be applied to any member of a struct.
It indicates that a member does not modify the state.
It will prevent using a variable from containing method in a local function and at the same time avoid performance costs related to making them available.

Now, let us understand by example.

Example

Point obj = new Point();
obj.X = 2;
obj.Y = 3;
Console.WriteLine(obj.Distance);
public struct Point
{
public double X { get; set; }
public double Y { get; set; }
public readonly double Distance => Math.Sqrt(X * X + Y * Y);
}

Summary

Now, I believe you will be able to implement "Using Declarations", "Nullable Reference Types", and "Readonly Struct Members" in C# 8.0.

In my next article, I will cover next three features such as "Null-Coalescing Assignment", "Async Streams", and "Property, Tuple, and Positional Patterns".

Previous parts of this series,

“C# - Top 10 New Features (Part 1 Of 4)”
“C# - Top 10 New Features (Part 2 Of 4)”

8 Comments

Join the conversation! Your thoughts help the community grow.

Ryder6y ago
Nice one...
- Pankajkumar Patel6y ago
  Thanks Ryder for the feedback
Chittaranjan Swain6y ago
Nice one......
- Pankajkumar Patel6y ago
  Thanks Chittaranjan Swain for the feedback
Mageshwaran R7y ago
Super Article..
- Pankajkumar Patel7y ago
  Thanks Magesh R for the feedback
Sourav Kumar Das7y ago
Nice Article.
- Pankajkumar Patel7y ago
  Thanks Sourav Kumar Das for the feedback