New Features Of C# 7.1

Default Value Expressions

A default value expression produces the default value for a type. Default value expressions are particularly useful in generic classes and methods

In C# 7.0

static void Main(string[] args)
{
    int a = default(int);
    int b = 2;
    Console.WriteLine($"a = {a}");
    Console.WriteLine($"a + b = {a + b}");
    int Add(int x, int y = default(int))
    {
        return x + y;
    }
    Console.WriteLine($"x +  y = {Add(5)}");
    Console.ReadLine();
}

In C# 7.1 enhancement has been done for Default Value Expressions and Type Inference and you can write the previous statement as follows

static void Main(string[] args)
{
    int a = default;
    int b = 2;
    Console.WriteLine($"a = {a}");
    Console.WriteLine($"a + b = {a + b}");
    int Add(int x, int y = default)
    {
        return x + y;
    }
    Console.WriteLine($"x +  y = {Add(5)}");
    Console.ReadLine();
}

Inferred Tuple Element Names

As you know, a tuple is a data structure that has a specific number and sequence of elements.

For example using Tuple in C# 7.0

static (decimal, decimal) GetPrice(int id)
{
    //Find product by id, then return price & discount
    return (100, 10);
}

Now, you can rewrite the code above in C# 7.1 as below

using System;

namespace ConsoleApp
{
    class Program
    {
        static (decimal price, decimal discount) GetPrice(int id)
        {
            //Find product by id, then return price & discount
            return (100, 10);
        }

        static void Main(string[] args)
        {
            var product = GetPrice(1);
            Console.WriteLine($"Price {product.price}$, Discount {product.discount}%");
            Console.ReadLine();
        }
    }
}

If you compile error, you need to change the C# version by right-clicking on your project->Properties->Build->Advanced->Select C# version > 7.0