using System;

using System.Collections.Generic;

using System.IO;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

​

namespace ConsoleApp1

{

    public class Program

    {

        public static void Main(string[] args)

        {

​

            try

            {

                int a = 2;

                int b = a / 0;

            }

            catch (DivideByZeroException e)

            {

                Console.WriteLine("Nicht durch 0 teilen!");

                Console.WriteLine(e.StackTrace);

            }

​

            Console.WriteLine("Weiter geht's");

​

            try

            {

                OnlyPositives(-1);

            }

            catch (NonNegativeException e)

            {

                Console.WriteLine(e.Message);

            }

​

            string text = ReadFile();

​

            Console.WriteLine(text);

​

        }

​

        static string ReadFile()

        {

            FileStream fs = null;

            try

            {

                fs = new FileStream("C:/asdf.txt", FileMode.Open);

                return fs.ReadByte().ToString();

            }catch(Exception e)

            {

                Console.WriteLine("Fehler beim Öffnen der Datei");

                return "404 not found";

            }

            finally

            {

                Console.WriteLine("Nach return");

                fs?.Close();

            }

​

        }

​

        class NonNegativeException : Exception

        {

            public int Number { get; private set; }

            public NonNegativeException(int number) : base($"Negative Zahl {number} eingegeben.")

            {

                Number = number;

            }

        }

​

        static void OnlyPositives(int x)

        {

            if (x < 0)

                throw new NonNegativeException(x);

​

            Console.WriteLine("Positive Nummer eingegeben");

​

        }

    }

}

​