New features in C# 7

[1] switch_with_patterns.cs

//See https://blogs.msdn.microsoft.com/dotnet/2016/08/24/whats-new-in-csharp-7-0/ for more details.

abstract class Shape {}
abstract class Polygon : Shape
{
    public virtual string NickName {get;}
    public virtual int Sides {get;}
}

class Square : Polygon
{
    public override string NickName => "Box";
    public override int Sides => 4;
}

class Triangle : Polygon
{
    public override string NickName => nameof(Triangle);
    public override int Sides => 4;    
}

class Circle : Shape {}

Shape shape = new Triangle();

//Switch statements with patterns
switch (shape)
{
    case Polygon p:
        Console.WriteLine($"{p.NickName} with {p.Sides} sides");
        break;
    default:
        Console.WriteLine($"{nameof(shape)} is not a polygon!");
        break;
    case null:
        throw new ArgumentNullException(nameof(shape)); //null case isn't matched by default case
}

[2] csharp_7_features.cs

//See https://blogs.msdn.microsoft.com/dotnet/2016/08/24/whats-new-in-csharp-7-0/ for more details.

//Tuples with deconstruction
(string, int) GetKeyAndValue()
{
    var sides = 3;
    return (GetNameOfShape(sides), sides);
    
    //Local function
    string GetNameOfShape(int noOfSides)
    {
        return noOfSides == 3 ? "triangle" : noOfSides == 4 ? "quadrilateral" : "unknown";
    }
}

var (key, val) = GetKeyAndValue();
Console.WriteLine(key); 

//Out variables
if (Int32.TryParse("42", out int result)) //result variable is declared here
{
    Console.WriteLine(result);
}

//Throw expressions
string Throws()
{
    string s = null;
    return s ?? throw new InvalidOperationException();
}

try
{
    Throws();
}
catch(Exception e)
{
    Console.WriteLine(e.Message);
}