After an amazing version 7.x in 2017, a new C# is being built and it is going to include new useful features.

However, if you don’t know the new features in C# 7.x, you must read the following posts; you can’t imagine how you can improve your code using this new features:

https://mteheran.wordpress.com/2017/12/01/features-c-7-0-7-1-7-2/
https://blogs.msdn.microsoft.com/dotnet/2017/03/09/new-features-in-c-7-0/

A specific roadmap for C# is not published, but now we can check the new features coming in the official repository: https://github.com/dotnet/csharplang/issues

Nullable reference types:

A great feature was introduced in C# 6. The Null-conditional operator helps to check if an object or variable is null before accessing an internal value. For example:

int? length = mynumbers?.Length;

Unfortunately, we cannot use this feature for String Type. In this case, the feature consists in allowing the developers to declare a String type as Nullable:

String? strVar = null;
var length = strVar?.Length;

Async Streams:

Basically, async streams are the asynchronous equivalent of IEnumerable. This feature allows the developers to use the async keyword within a foreach as the following syntax:

foreach await (string s in asyncStream)
In order to use that code, you have to define the collection as IAsyncEnumerable:

async IAsyncEnumerable MethodName()
Default Interface Implementations:

Let’s start checking the following code:

Interface ICal 
{
    Void TurnOn();
}
Calculator : ICal
{
   void TurnOn()
   {
   }
}

Everything is easier using interfaces and as we know, we can use multiple implementations. But if we want to add a new method within the interface, all the classes implementing that interface need to create a local method with the same name and return the same value.

Now in C# 8, we can implement a method directly within the interface like this:

Interface ICar 
{
    Void TurnOn();
}
Car : ICar
{
   void TurnOn()
   {
   }
}
Interface ICal 
{
    Void TurnOn();
    double SumNumbers( double number1, double number2 ) 
    {
       return number1+ number2 
    }
}
Calculator : ICal
{
   void TurnOn()
   {
   }
}

Extension Everything:

This proposal was reported as an issue in github and you can see the summary in the following link:

https://github.com/dotnet/roslyn/issues/11159

For example, an extension of a class person:

extension MyPersonExtension extends Person 
{ 
   public int NumberOfFingers() 
   { 
      get { … } 
   } 
}

You can find more information in the following links:

https://www.infoq.com/news/2017/08/CSharp-8

https://channel9.msdn.com/Blogs/Seth-Juarez/A-Preview-of-C-8-with-Mads-Torgersen#time=32m11s