Dùng if và goto để tạo vòng lặp

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

namespace lenh_goto
{
    class Program
    {
        static void Main(string[] args)
        {
            int i=1;
            lap:
            if (i <= 10)
            {
                Console.Write(i + " ");
                i++;
           
             }
            goto lap;

        }
    }
}  

Tạo menu cấp 1 đơn giản, cho phép dùng phím mũi tên lên xuống để di chuyển vị trí chọn

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

namespace Bai16
{
    class Program
    {
        static void XuatMenu(int chon)
        {
            string[] str = {"Chuc nang 1" , "Chuc nang 2", "Chuc nang 3", "Chuc nang 4", "Thoat"};
            int x = 20;
            int[] y = {5, 7, 9, 11, 13};
            Console.CursorLeft = x;
            Console.CursorTop = 3;
            Console.ForegroundColor = ConsoleColor.White;
            Console.BackgroundColor = ConsoleColor.Black;
            Console.Write("BAI TAP MENU");

            Console.ForegroundColor = ConsoleColor.Red;
            for (int i = 0; i < str.Length; i++)
            {
                if (i == chon)
                    Console.BackgroundColor = ConsoleColor.Cyan;
                else
                    Console.BackgroundColor = ConsoleColor.Green;
                Console.CursorLeft = x;
                Console.CursorTop = y[i];
                Console.Write(str[i]);
            }

        }

        static void XuLy()
        {
            int i = 0;
            ConsoleKeyInfo key;
            while (true)
            {
                XuatMenu(i);
                Console.CursorLeft = 40;
                Console.CursorTop =  18;
                key = Console.ReadKey();
                if (key.Key == ConsoleKey.DownArrow && i < 4)
                    i++;
                if (key.Key == ConsoleKey.UpArrow && i > 0)
                    i--;
                if (key.Key == ConsoleKey.Enter && i == 4)
                    break;
             
                else if(key.Key == ConsoleKey.Enter)
                    Console.Write("Ban dang chon chuc nang " +(i+1).ToString());
            }

        }
        static void Main(string[] args)
        {
            XuLy();
        }  

Liệt kê n số nguyên tố đầu tiên

using System;

using System.Collections.Generic;

using System.Linq; using System.Text;
namespace Bai_Tap_13 //Liệt kê n số nguyên tố đầu tiên  

{
    class Program
    {
        static bool KTSNT(int n)
        {
            if (n == 1 || n == 2 || n==3)
                return true;
            for (int i = 2; i <= n / 2; i++)
                if (n % i == 0)
                    return false;
            return true;
        }
        static void Output(ref int n)
        {
            int dem=0;
            for (int i = 1; dem != n; i++)
            {
                if (KTSNT(i) == true)
                {
                    Console.Write(i + "\t");
                    dem++;
                }
            }
        }
        static void Main(string[] args)
        {
            int luachon, n;
            do
            {
                Console.Write("\nNhap vao so n = ");
                n = int.Parse(Console.ReadLine());
                Console.Write("\n" + n + " so nguyen to dau tien la: \n\n");
                Output(ref n);
                Console.Write("\n\nContinue? (1:Exit) => ");
                luachon = int.Parse(Console.ReadLine());
            } while (luachon != 1);
            Console.Write("\n");
        }
    }
}  

Ứng dụng lớp điểm ký tự viết trò chơi rắn săn mồi

CDIEM.cs

PHP Code:

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

namespace BT19_ransanmoidos
{
    class CDIEM
    {
        public int x;
        public int y;
        public char c;

        public CDIEM()
        {
        }

        public CDIEM(int xx, int yy, char cc)
        {
            x = xx;
            y = yy;
            c = cc;
        }

        public bool KiemTraX(int xx)
        {
            if (xx <= 0 || xx >= Console.WindowWidth)
            {
                return false;
            }
            return true;
        }
        public bool KiemTraY(int yy)
        {
            if (yy <= 0 || yy >= Console.WindowHeight)
            {
                return false;
            }
            return true;
        }

        public void DichPhai(int k)
        {
            x += k;
        }
        public void DichTrai(int k)
        {
            x -= k;
        }
        public void DichLen(int k)
        {
            y -= k;
        }
        public void DichXuong(int k)
        {
            y += k;
        }

        public void Xuat()
        {
            Console.SetCursorPosition(x, y);
            Console.Write(c);
        }

        public void Xoa()
        {
            Console.Clear();
        }

        public float KhoangCach(CDIEM M)
        {
            return 0;
        }
        public int KhoangCachX()
        {
            return x;
        }
        public int KhoangCachY()
        {
            return y;
        }

    }
}  

Program.cs

PHP Code:

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

namespace BT19_ransanmoidos
{
    class Program
    {
        static ArrayList list = new ArrayList();
        static CDIEM thucan;
        static Random rnd = new Random();
        static int TOCDO = 100;
        static String huong = "Phai";
        // ký tự đại diện cho rẳn
        const char KYTU = '0';

        static void Main(string[] args)
        {
            Console.CursorVisible = false;

            list.Add(new CDIEM(0, 0, KYTU));
            TaoThucAn();

            RanChay();

            Console.Clear();
            Console.SetCursorPosition(0, 0);
            Console.ForegroundColor = ConsoleColor.Yellow;
            Console.WriteLine("YOU LOSE!!!");
            Console.WriteLine("Press Any Key To Exit!!!");
            Console.Read();
        }

        static void RanChay()
        {
            do
            {
                NhanPhimBam();

                // Lấy đoạn cuối trong rắn
                CDIEM doanCuoi = (CDIEM)list[list.Count - 1];
                CDIEM c = new CDIEM(doanCuoi.x, doanCuoi.y, KYTU);

                // Thực hiện dịch chuyển rắn trong đoạn cuối.
                switch (huong)
                {
                    case "Len":
                        c.DichLen(1);
                        break;
                    case "Xuong":
                        c.DichXuong(1);
                        break;
                    case "Trai":
                        c.DichTrai(1);
                        break;
                    case "Phai":
                        c.DichPhai(1);
                        break;
                }
                if (TimXTrongList(c))
                {
                    break;
                }
                // Thêm một đoạn vào list.
                list.Add(c);
                // Remove phần tử đầu tiên khỏi  list.
                list.RemoveAt(0);

                // kiểm tra có thức ăn chưa.
                KiemTraThucAn();

                try
                {
                    VeLai();
                }
                catch (Exception)
                { }

                Thread.Sleep(TOCDO);

            } while (KiemTraTiepTuc());
        }

        static void VeLai()
        {
            Console.Clear();

            // Vẽ rắn.
            foreach (CDIEM c in list)
            {
                c.Xuat();
            }

            // Ve thuc an
            thucan.Xuat();
        }

        static void TaoThucAn()
        {
            int hang = rnd.Next(1, Console.WindowWidth);
            int cot = rnd.Next(1, Console.WindowHeight);

            thucan = new CDIEM(hang, cot, 'G');
            //thucan = new CDIEM(5, 5, 'G');
        }

        static void KiemTraThucAn()
        {
            CDIEM c = (CDIEM)list[list.Count - 1];

            if (c.x == thucan.x && c.y == thucan.y)
            {
                CDIEM cDau = (CDIEM)list[0];
                CDIEM cMoi = new CDIEM(cDau.x, cDau.y, KYTU);
                list.Insert(0, cMoi);
                TaoThucAn();
            }
        }

        static bool KiemTraTiepTuc()
        {
            CDIEM c = (CDIEM)list[list.Count - 1];
            if (c.y < 0 || c.y >= Console.WindowHeight - 1 ||
                c.x < 0 || c.x >= Console.WindowWidth - 1)
            {
                return false;
            }
            return true;
        }

        static bool TimXTrongList(CDIEM x)
        {
            foreach (CDIEM c in list)
            {
                if (c.x == x.x && c.y == x.y)
                {
                    return true;
                }
            }
            return false;
        }

        static void NhanPhimBam()
        {
            while (Console.KeyAvailable)
            {
                switch (Console.ReadKey(true).Key)
                {
                    case ConsoleKey.UpArrow:
                        huong = "Len";
                        break;
                    case ConsoleKey.DownArrow:
                        huong = "Xuong";
                        break;
                    case ConsoleKey.LeftArrow:
                        huong = "Trai";
                        break;
                    case ConsoleKey.RightArrow:
                        huong = "Phai";
                        break;
                }
            }
        }

    }
}  

Đây là bài viết mình sưu tằm, có  vần đề gì các bạn thông cảm nhé