// new features in .NET 5 preview 4

net5p4.cs

// new features in .NET 5 preview 4

using System;
using System.Collections.Generic;

interface IA { int A(); }
interface IB : IA { int B(); }
interface IC : IA { int C(); }

class Ab : IB, IC
{
    public int A() => 2;
    public int B() => 3;
    public int C() => 5;
}

class Program
{
    static void Main()
    {
        // native int
        nint i = 1;
        nint u = 2;
        Console.WriteLine(i + u);
    }

    // target-typed new
    static Dictionary<string, int> d = new()
    {
        { "a", 1 },
    };

    // pattern V3 (and, or, not, simple type, parenthesized...)
    static int M(object obj) => obj switch
    {
        IB b and IC c => b.A() * b.B() * c.C(), 
        (IA or IB) and var a  => a.A(),
        DateTime => 1,
        not null => 0,
        null => -1,
    };

    // pattern V3 (rerational, exhaustivity check)
    static int M(int value) => value switch
    {
        < 100 => 1,
        >= 100 and <= 500 => 2,
        > 500 => 3,
    };

    // pattern V3 (byte exhaustivity check)
    static int M(byte value) => value switch
    {
        <= 31 => 0,
        32 => 2,
        <= 47 => 3,
        <= 57 => 4,
        <= 64 => 3,
        <=90 => 5,
        <= 96 => 3,
        <= 122 => 5,
        <= 126 => 3,
        127 => 0,
    };
}