C#-Code

using System;
using static System.Console;

namespace zahlentausch_181  {

    class Program    {

        static void Main()        {
            int[] input = new int[2];

            do  {
                bool[] bo_input_ok = new bool[] { false, false };

                while (!bo_input_ok[0])                {
                    "Bitte zahl_1 eingeben: ".Message();
                    bo_input_ok[0] = int.TryParse(ReadLine(), out input[0]);
                }
                while (!bo_input_ok[1])                {
                    "Bitte zahl_2 eingeben: ".Message();
                    bo_input_ok[1] = int.TryParse(ReadLine(), out input[1]);
                }

                input = input.tausche();

                ("zahl_1: " + input[0].ToString() + Environment.NewLine + "zahl_2: " + input[1].ToString()).MessageLine();

            }   while (!("again? exit ESC".EndMessage().Key == ConsoleKey.Escape));
        }
    }

    public static class MyExtensions    {

        public static void Message(this string s) => Write(s);

        public static void MessageLine(this string s) => WriteLine(s); 

        public static ConsoleKeyInfo EndMessage(this string s)
        { s.MessageLine(); return ReadKey(true); }

        public static int[] tausche(this int[] input)        {
            int[] result = new int[2];
            input.CopyTo(result, 0);
            result[0] += result[1];
            result[1] = result[0] - result[1];
            result[0] -= result[1];
            return result;
        }
    }
}

C#-Code

namespace A181_Variablenspielerei
{
    class Program
    {
        static void Main(string[] args)
        {
            int a = 14;
            int b = 21;
            Tauschen(ref a, ref b);
        }

        static void Tauschen(ref int a, ref int b)
        {
            b += a;
            a = b - a;
            b = b - a;
        }
    }
}

C#-Code

using System;
					
public class Program
{
	public static void Main()
	{
		int a = 5;
		int b = 10;
		
		new Action<int, int>((xa, xb) => {a = xb;b = xa;})(a, b);
	}
}

C#-Code

            int a, b;
            Console.WriteLine("Gib die erste Zahl ein:");
            a =Convert.ToInt32( Console.ReadLine());
            Console.WriteLine("Gib die zweite Zahl ein:");
            b = Convert.ToInt32(Console.ReadLine());
            Console.WriteLine("Deine eingaben sind: {0} und {1}", a, b);
            Console.WriteLine("Die Werte der Variablen werden nun ohne neue Variable vertauscht.");
            b = b + a;
            a = b - a;
            b = b - a;
            Console.WriteLine("Die neuen Werte sind {0} und {1}", a, b);
            Console.ReadLine();

C#-Code

using System;

namespace VariablenTausch
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                int a = Convert.ToInt32(args[0]);
                int b = Convert.ToInt32(args[1]);

                Console.WriteLine("a = {0}\nb = {1}\n", a, b);

                (a, b) = (b, a);    // System.ValueTuple

                Console.WriteLine("a = {0}\nb = {1}", a, b);
            }
            catch(Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.ReadKey();
        }
    }
}

C#-Code

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace übung181
{
    class Program
    {
        static void Main(string[] args)
        {
            int c = Convert.ToInt32(Console.ReadLine());
            int x = Convert.ToInt32(Console.ReadLine());

            x = x + c;
            c = x - c;
            x = x - c;
            
            Console.WriteLine(c);
            Console.WriteLine(x);
            Console.ReadKey();
        }
    }
}