C# 7 Features

Program.cs

using System;

namespace CSharp7Features
{
    class Program
    {
        static void Main(string[] args)
        {
            OutVariables();

            PatternMatching("123");

            BetterSwitchCase("123");
            BetterSwitchCase("Foo");

            // ValueTuple NuGet Package Required:
            // Install-Package "System.ValueTuple"
            var tuplesYay = TuplesYay();
            Console.WriteLine($"Tuples Result: {tuplesYay.result}, Error: {tuplesYay.error}");

            LocalFunction();

            Console.ReadLine();
        }

        private static void OutVariables()
        {
            string s = "123";
            if (int.TryParse(s, out var i))
            {
                Console.WriteLine($"s is the integer {i}.");
            }
        }

        private static void PatternMatching(object obj)
        {
            if(obj is string s && int.TryParse(s, out var i))
            {
                Console.WriteLine($"Input Variable was a string ({s}), and parsed to the int {i}.");
            }
        }

        private static void BetterSwitchCase(string s)
        {
            switch (s)
            {
                case string x when x.Length == 3 && int.TryParse(x, out int i):
                    Console.WriteLine($"s is a string that parses to {i}");
                    break;
                default:
                    Console.WriteLine("No Match.");
                    break;
            }
        }

        // ValueTuple NuGet Package Required:
        // Install-Package "System.ValueTuple"
        private static (bool result, string error) TuplesYay()
        {
            return (true, "Foo");
        }

        private static void LocalFunction()
        {
            // Instead of having to declare a Func<> or Action<>. Can even call itself!
            void Log(string message) {
                Console.WriteLine($"[{DateTime.Now.ToString("yyyy-MM-dd HH:mm:ss")}] {message}");
            }

            (int current, int previous) Fib(int i)
            {
                if (i == 0)
                {
                    Log("Fib of 0: 1");
                    return (1, 0);
                }
                var (p, pp) = Fib(i - 1);
                var tmpResult = (p + pp, p);

                Log($"Fib of {i}: {tmpResult.Item1}");
                return tmpResult;
            }

            (int result, int previous) = Fib(5);

            Log("Final Result: " + result);
        }
    }
}