A 3 feladat

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

namespace gyakorlofeladatok
{
  class Program
  {
    static void tombfeltoltes(int[] tomb, int elsoelem, int utolsoelem, int elemszam, bool prime)
    {
      Random vel = new Random();
      bool talal;
      if(elsoelem > utolsoelem)
      {
        int cs;
        cs = elsoelem;
        elsoelem = utolsoelem;
        utolsoelem = cs;
      }
      if(elemszam < 2)
      {
        elemszam = utolsoelem - elsoelem + 1;
      }
      if (prime == true)
      {
        do
        {
          tomb[0] = vel.Next(elsoelem, utolsoelem + 1);
        }while (!isprime(tomb[0]));
      }
      else
      {
        tomb[0] = vel.Next(elsoelem, utolsoelem + 1);
      }
      for (int i = 1; i < elemszam; i++)
      {
        do
        {
          talal = false;
          if (prime == true)
          {
            do
            {
              tomb[i] = vel.Next(elsoelem, utolsoelem + 1);
            } while (!isprime(tomb[i]));
          }
          else
          {
            tomb[i] = vel.Next(elsoelem, utolsoelem + 1);
          }
          for (int j = 0; j < i; j++)
          {
            if (tomb[j] == tomb[i])
            {
              talal = true;
            }
          }
        } while (talal);
      }
    }
    static bool isprime(int szam)
    {
      if (szam == 0 || szam == 1)
      {
        return false;
      }
      else if (szam == 2)
      {
        return true;
      }
      else
      {
        bool prim = true;
        for (int i = 2; i < szam; i++ )
        {
          if (szam % i == 0)
          {
            prim = false;
            break;
          }
        }
        return prim;
      }
    }
    static void Main(string[] args)
    {
      Console.Write("Adja meg a feladat számát: ");
      string menu = Console.ReadLine();
      int elemszam2 = 10;
      int[] primtomb = new int[elemszam2];
      int elsoelem = 2, utolsoelem = 10000;
      switch (menu)
      {
        case "1":
          tombfeltoltes(primtomb, elsoelem, utolsoelem, elemszam2, true);
          for (int i = 0; i < 10; i++ )
          {
            if (i != 9)
            {
              Console.Write("{0}, ", primtomb[i]);
            }
            else
            {
              Console.WriteLine("{0}", primtomb[i]);
            }

          }
          int maxindex = 0;
          for (int j = 1; j < 10; j++)
          {
            if(primtomb[j] > primtomb[maxindex])
            {
              maxindex = j;
            }
          }
          Console.WriteLine("A tömb legnagyobb eleme: {0}", primtomb[maxindex]);
        break;
        case "2":
        Console.Write("Adja meg a értékét: ");
        string szam = Console.ReadLine();
        double a = Convert.ToDouble(szam);
        Console.Write("Adja meg b értékét: ");
        szam = Console.ReadLine();
        double b = Convert.ToDouble(szam);
        if (a != b && b < a)
        {
          double cs;
          cs = b;
          b = a;
          a = cs;
        }
        int minimum = Convert.ToInt32(Math.Ceiling(a));
        int maximum = Convert.ToInt32(Math.Floor(b));
        int k, db=0, db2 = 0;
        for (int j = 0; j < 2; j++ )
        {
          for (k = minimum; k <= maximum; k++)
          {
            if(isprime(k))
            {
              if (j == 0)
              {
                db++;
              }
              else
              {
                Console.Write(k);
                if(db != db2-1)
                {
                  Console.Write(", ");
                  db++;
                }
              }
            }
          }
          if (j == 0)
          {
            db2 = db;
            db = 0;
          }
        }
        break;
        case "3":
        int eelem = 10;
        int uelem = 99;
        int elemszam = 10;
        int[] akarmi = new int[elemszam];
        tombfeltoltes(akarmi, eelem, uelem, elemszam, false);
        for (int i = 0; i < elemszam; i++)
        {
          if(akarmi[i] % 2 == 0)
          {
            Console.Write(akarmi[i]);
            Console.Write("  ");
          }
        }
        break;
      }
      Console.ReadKey();
    }
  }
}