With Visual Studio 2017.3, came the first "point" release or minor update to C#, 7.1. This release adds three new features on top of C#7.0: async main method, default literal expressions and inferred tuple element names.

In this post, I will cover how to enable C# 7.1 and the new features which came with it.

How to select C# version

By default, the 7.1 features are turned off. To enable 7.1 features, you need to change the language version setting of the project in Visual Studio.

Right-click the project, select properties. Go to Build tab and click Advanced button: 

 

 Select C# latest Minor version:

 

Async Main

Now you can make the Main entry point method async, and return Task or Task<int>. 

Earlier, if you called an async method from the Main method, you had to call it synchronously by calling method GetAwaier().GetResult() on it.

static void Main()
{
    AsyncMethod().GetAwaiter().GetResult();
}

 Now, you can make the Main method async and await any async call inside:

static async Task Main()
{
    await AsyncMethod();
}

 

Default Literal Expressions

Assigning default value has been simplified, let's see how:

Before C# 7.1:

bool hasValue = default(bool);
Action<int, bool> action = default(Action<int,bool>);

Now, you don't need to specify the type on the right-hand side of initialization:

bool hasValue = default;
Action<int, bool> action = default;

 

Inferred Tuple Element Names

Tuples were enhanced in C# 7.0 release, check out what changed in this post. 

In C# 7.1, tuple element names can be inferred when it is initialized:

int low = 1;
int high = 10;

var a = (low, high);

Is same as declaring:

(int low, int high) t = (low, high);