using System;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;

namespace BlazorServer.Entities
{
    public class RoomOrderDetail
    {
        public int Id { get; set; }

        [Required]
        public string UserId { get; set; }

        [Required]
        public string StripeSessionId { get; set; }

        public DateTime CheckInDate { get; set; }

        public DateTime CheckOutDate { get; set; }

        public DateTime ActualCheckInDate { get; set; }

        public DateTime ActualCheckOutDate { get; set; }

        public long TotalCost { get; set; }

        public int RoomId { get; set; }

        public bool IsPaymentSuccessful { get; set; }

        [Required]
        public string Name { get; set; }

        [Required]
        public string Email { get; set; }

        public string Phone { get; set; }

        [ForeignKey("RoomId")]
        public HotelRoom HotelRoom { get; set; }

        public string Status { get; set; }
    }
}

namespace BlazorServer.Common
{
    public static class BookingStatus
    {
        public const string Pending = "Pending";
        public const string Booked = "Booked";
        public const string CheckedIn = "CheckedIn";
        public const string CheckedOutCompleted = "CheckedOut";
        public const string NoShow = "NoShow";
        public const string Cancelled = "Cancelled";
    }
}

namespace BlazorServer.DataAccess
{
    public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
    {
        public DbSet<RoomOrderDetail> RoomOrderDetails { get; set; }

        // ...
    }
}

dotnet tool update --global dotnet-ef --version 5.0.4
dotnet build
dotnet ef migrations --startup-project ../../BlazorWasm/BlazorWasm.WebApi/ add AddRoomOrderDetails --context ApplicationDbContext
dotnet ef --startup-project ../../BlazorWasm/BlazorWasm.WebApi/ database update --context ApplicationDbContext

using System;
using System.ComponentModel.DataAnnotations;

namespace BlazorServer.Models
{
    public class RoomOrderDetailsDTO
    {
        public int Id { get; set; }

        [Required]
        public string UserId { get; set; }

        [Required]
        public string StripeSessionId { get; set; }

        [Required]
        public DateTime CheckInDate { get; set; }

        [Required]
        public DateTime CheckOutDate { get; set; }

        public DateTime ActualCheckInDate { get; set; }

        public DateTime ActualCheckOutDate { get; set; }

        [Required]
        public long TotalCost { get; set; }

        [Required]
        public int RoomId { get; set; }

        public bool IsPaymentSuccessful { get; set; }

        [Required]
        public string Name { get; set; }

        [Required]
        public string Email { get; set; }

        public string Phone { get; set; }

        public HotelRoomDTO HotelRoomDTO { get; set; }

        public string Status { get; set; }
    }
}

namespace BlazorServer.Models.Mappings
{
    public class MappingProfile : Profile
    {
        public MappingProfile()
        {
            // ... 
            CreateMap<RoomOrderDetail, RoomOrderDetailsDTO>().ReverseMap(); // two-way mapping
        }
    }
}

namespace BlazorServer.Services
{
    public interface IRoomOrderDetailsService
    {
        Task<RoomOrderDetailsDTO> CreateAsync(RoomOrderDetailsDTO details);

        Task<List<RoomOrderDetailsDTO>> GetAllRoomOrderDetailsAsync();

        Task<RoomOrderDetailsDTO> GetRoomOrderDetailAsync(int roomOrderId);

        Task<bool> IsRoomBookedAsync(int RoomId, DateTime checkInDate, DateTime checkOutDate);

        Task<RoomOrderDetailsDTO> MarkPaymentSuccessfulAsync(int id);

        Task<bool> UpdateOrderStatusAsync(int RoomOrderId, string status);
    }
}

namespace BlazorServer.Services
{
    public class RoomOrderDetailsService : IRoomOrderDetailsService
    {
        private readonly ApplicationDbContext _dbContext;
        private readonly IMapper _mapper;
        private readonly IConfigurationProvider _mapperConfiguration;

        public RoomOrderDetailsService(ApplicationDbContext dbContext, IMapper mapper)
        {
            _dbContext = dbContext ?? throw new ArgumentNullException(nameof(dbContext));
            _mapper = mapper ?? throw new ArgumentNullException(nameof(mapper));
            _mapperConfiguration = mapper.ConfigurationProvider;
        }

        public async Task<RoomOrderDetailsDTO> CreateAsync(RoomOrderDetailsDTO details)
        {
            var roomOrder = _mapper.Map<RoomOrderDetail>(details);
            roomOrder.Status = BookingStatus.Pending;
            var result = await _dbContext.RoomOrderDetails.AddAsync(roomOrder);
            await _dbContext.SaveChangesAsync();
            return _mapper.Map<RoomOrderDetailsDTO>(result.Entity);
        }

        public Task<List<RoomOrderDetailsDTO>> GetAllRoomOrderDetailsAsync()
        {
            return _dbContext.RoomOrderDetails
                            .Include(roomOrderDetail => roomOrderDetail.HotelRoom)
                            .ProjectTo<RoomOrderDetailsDTO>(_mapperConfiguration)
                            .ToListAsync();
        }

        public async Task<RoomOrderDetailsDTO> GetRoomOrderDetailAsync(int roomOrderId)
        {
            var roomOrderDetailsDTO = await _dbContext.RoomOrderDetails
                                            .Include(u => u.HotelRoom)
                                                .ThenInclude(x => x.HotelRoomImages)
                                            .ProjectTo<RoomOrderDetailsDTO>(_mapperConfiguration)
                                            .FirstOrDefaultAsync(u => u.Id == roomOrderId);

            roomOrderDetailsDTO.HotelRoomDTO.TotalDays =
                roomOrderDetailsDTO.CheckOutDate.Subtract(roomOrderDetailsDTO.CheckInDate).Days;
            return roomOrderDetailsDTO;
        }

        public Task<bool> IsRoomBookedAsync(int RoomId, DateTime checkInDate, DateTime checkOutDate)
        {
            return _dbContext.RoomOrderDetails
                .AnyAsync(
                    roomOrderDetail =>
                        roomOrderDetail.RoomId == RoomId &&
                        roomOrderDetail.IsPaymentSuccessful &&
                        (
                            (checkInDate < roomOrderDetail.CheckOutDate && checkInDate > roomOrderDetail.CheckInDate) ||
                            (checkOutDate > roomOrderDetail.CheckInDate && checkInDate < roomOrderDetail.CheckInDate)
                        )
                );
        }

        public Task<RoomOrderDetailsDTO> MarkPaymentSuccessfulAsync(int id)
        {
            throw new NotImplementedException();
        }

        public Task<bool> UpdateOrderStatusAsync(int RoomOrderId, string status)
        {
            throw new NotImplementedException();
        }
    }
}

namespace BlazorWasm.WebApi
{
    public class Startup
    {
        // ...

        public void ConfigureServices(IServiceCollection services)
        {
            services.AddScoped<IRoomOrderDetailsService, RoomOrderDetailsService>();
            // ...

namespace BlazorWasm.Client.Services
{
    public interface IClientRoomOrderDetailsService
    {
        Task<RoomOrderDetailsDTO> MarkPaymentSuccessfulAsync(RoomOrderDetailsDTO details);
        Task<RoomOrderDetailsDTO> SaveRoomOrderDetailsAsync(RoomOrderDetailsDTO details);
    }
}

namespace BlazorWasm.Client.Services
{
    public class ClientRoomOrderDetailsService : IClientRoomOrderDetailsService
    {
        private readonly HttpClient _httpClient;

        public ClientRoomOrderDetailsService(HttpClient httpClient)
        {
            _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
        }

        public Task<RoomOrderDetailsDTO> MarkPaymentSuccessfulAsync(RoomOrderDetailsDTO details)
        {
            throw new NotImplementedException();
        }

        public Task<RoomOrderDetailsDTO> SaveRoomOrderDetailsAsync(RoomOrderDetailsDTO details)
        {
            throw new NotImplementedException();
        }
    }
}

namespace BlazorWasm.Client
{
    public class Program
    {
        public static async Task Main(string[] args)
        {
            var builder = WebAssemblyHostBuilder.CreateDefault(args);
            // ...
            builder.Services.AddScoped<IClientRoomOrderDetailsService, ClientRoomOrderDetailsService>();
            // ...
        }
    }
}

using BlazorServer.Models;

namespace BlazorWasm.Client.Models.ViewModels
{
    public class HotelRoomBookingVM
    {
        public RoomOrderDetailsDTO OrderDetails { get; set; }
    }
}

@page "/hotel/room-details/{Id:int}"

@inject IJSRuntime JsRuntime
@inject ILocalStorageService LocalStorage
@inject IClientHotelRoomService HotelRoomService

@if (HotelBooking?.OrderDetails?.HotelRoomDTO?.HotelRoomImages == null)
{
    <div class="spinner"></div>
}
else
{

}

@code {
    [Parameter]
    public int? Id { get; set; }

    HotelRoomBookingVM HotelBooking  = new HotelRoomBookingVM();
    int NoOfNights = 1;

    protected override async Task OnInitializedAsync()
    {
        try
        {
            HotelBooking.OrderDetails = new RoomOrderDetailsDTO();
            if (Id != null)
            {
                if (await LocalStorage.GetItemAsync<HomeVM>(ConstantKeys.LocalInitialBooking) != null)
                {
                    var roomInitialInfo = await LocalStorage.GetItemAsync<HomeVM>(ConstantKeys.LocalInitialBooking);
                    HotelBooking.OrderDetails.HotelRoomDTO = await HotelRoomService.GetHotelRoomDetailsAsync(
                        Id.Value, roomInitialInfo.StartDate, roomInitialInfo.EndDate);
                    NoOfNights = roomInitialInfo.NoOfNights;
                    HotelBooking.OrderDetails.CheckInDate = roomInitialInfo.StartDate;
                    HotelBooking.OrderDetails.CheckOutDate = roomInitialInfo.EndDate;
                    HotelBooking.OrderDetails.HotelRoomDTO.TotalDays = roomInitialInfo.NoOfNights;
                    HotelBooking.OrderDetails.HotelRoomDTO.TotalAmount =
                        roomInitialInfo.NoOfNights * HotelBooking.OrderDetails.HotelRoomDTO.RegularRate;
                }
                else
                {
                    HotelBooking.OrderDetails.HotelRoomDTO = await HotelRoomService.GetHotelRoomDetailsAsync(
                        Id.Value, DateTime.Now, DateTime.Now.AddDays(1));
                    NoOfNights = 1;
                    HotelBooking.OrderDetails.CheckInDate = DateTime.Now;
                    HotelBooking.OrderDetails.CheckOutDate = DateTime.Now.AddDays(1);
                    HotelBooking.OrderDetails.HotelRoomDTO.TotalDays = 1;
                    HotelBooking.OrderDetails.HotelRoomDTO.TotalAmount =
                        HotelBooking.OrderDetails.HotelRoomDTO.RegularRate;
                }
            }
        }
        catch (Exception e)
        {
            await JsRuntime.ToastrError(e.Message);
        }
    }
}

namespace BlazorWasm.Client.Services
{
    public class ClientHotelRoomService : IClientHotelRoomService
    {
        private readonly HttpClient _httpClient;

        public ClientHotelRoomService(HttpClient httpClient)
        {
            _httpClient = httpClient ?? throw new ArgumentNullException(nameof(httpClient));
        }

        public Task<HotelRoomDTO> GetHotelRoomDetailsAsync(int roomId, DateTime checkInDate, DateTime checkOutDate)
        {
            // How to url-encode query-string parameters properly
            var uri = new UriBuilderExt(new Uri(_httpClient.BaseAddress, $"/api/hotelroom/{roomId}"))
                            .AddParameter("checkInDate", $"{checkInDate:yyyy'-'MM'-'dd}")
                            .AddParameter("checkOutDate", $"{checkOutDate:yyyy'-'MM'-'dd}")
                            .Uri;
            return _httpClient.GetFromJsonAsync<HotelRoomDTO>(uri);
        }

        public Task<IEnumerable<HotelRoomDTO>> GetHotelRoomsAsync(DateTime checkInDate, DateTime checkOutDate)
        {
           // ...
        }
    }
}

@if (HotelBooking?.OrderDetails?.HotelRoomDTO?.HotelRoomImages == null)
{
    <div class="spinner"></div>
}
else
{
    <div class="mt-4 mx-4 px-0 px-md-5 mx-md-5">
        <div class="row p-2 my-3 " style="border-radius:20px; ">
            <div class="col-12 col-lg-7 p-4" style="border: 1px solid gray">
                <div class="row px-2 text-success border-bottom">
                    <div class="col-8 py-1"><p style="font-size:x-large;margin:0px;">Selected Room</p></div>
                    <div class="col-4 p-0"><a href="hotel/rooms" class="btn btn-secondary btn-block">Back to Room's</a></div>
                </div>
                <div class="row">
                    <div class="col-6">
                        <div id="" class="carousel slide mb-4 m-md-3 m-0 pt-3 pt-md-0" data-ride="carousel">
                            <div id="carouselExampleIndicators" class="carousel slide" data-ride="carousel">
                                <ol class="carousel-indicators">
                                    <li data-target="#carouselExampleIndicators" data-slide-to="0" class="active"></li>
                                    <li data-target="#carouselExampleIndicators" data-slide-to="1"></li>
                                </ol>
                                <div class="carousel-inner">
                                    <div class="carousel-item active">
                                        <img class="d-block w-100" src="images/slide1.jpg" alt="First slide">
                                    </div>
                                </div>
                                <a class="carousel-control-prev" href="#carouselExampleIndicators" role="button" data-slide="prev">
                                    <span class="carousel-control-prev-icon" aria-hidden="true"></span>
                                    <span class="sr-only">Previous</span>
                                </a>
                                <a class="carousel-control-next" href="#carouselExampleIndicators" role="button" data-slide="next">
                                    <span class="carousel-control-next-icon" aria-hidden="true"></span>
                                    <span class="sr-only">Next</span>
                                </a>
                            </div>
                        </div>
                    </div>
                    <div class="col-6">
                        <span class="float-right pt-4">
                            <span class="float-right">Occupancy : @HotelBooking.OrderDetails.HotelRoomDTO.Occupancy adults </span><br />
                            <span class="float-right pt-1">Size : @HotelBooking.OrderDetails.HotelRoomDTO.SqFt sqft</span><br />
                            <h4 class="text-warning font-weight-bold pt-5">
                                <span style="border-bottom:1px solid #ff6a00">
                                    @HotelBooking.OrderDetails.HotelRoomDTO.TotalAmount.ToString("#,#.00#;(#,#.00#)")
                                </span>
                            </h4>
                            <span class="float-right">Cost for @HotelBooking.OrderDetails.HotelRoomDTO.TotalDays nights</span>
                        </span>
                    </div>
                </div>
                <div class="row p-2">
                    <div class="col-12">
                        <p class="card-title text-warning" style="font-size:xx-large">@HotelBooking.OrderDetails.HotelRoomDTO.Name</p>
                        <p class="card-text" style="font-size:large">
                            @((MarkupString)@HotelBooking.OrderDetails.HotelRoomDTO.Details)
                        </p>
                    </div>

                </div>
            </div>
}

@if (HotelBooking?.OrderDetails?.HotelRoomDTO?.HotelRoomImages == null)
{
    <div class="spinner"></div>
}
else
{
  // ...
             
            <div class="col-12 col-lg-5 p-4 2 mt-4 mt-md-0" style="border: 1px solid gray;">
                <EditForm Model="HotelBooking" class="container" OnValidSubmit="HandleCheckout">
                    <div class="row px-2 text-success border-bottom"><div class="col-7 py-1"><p style="font-size:x-large;margin:0px;">Enter Details</p></div></div>

                    <div class="form-group pt-2">
                        <label class="text-warning">Name</label>
                        <InputText @bind-Value="HotelBooking.OrderDetails.Name" type="text" class="form-control" />
                    </div>
                    <div class="form-group pt-2">
                        <label class="text-warning">Phone</label>
                        <InputText @bind-Value="HotelBooking.OrderDetails.Phone" type="text" class="form-control" />
                    </div>
                    <div class="form-group">
                        <label class="text-warning">Email</label>
                        <InputText @bind-Value="HotelBooking.OrderDetails.Email" type="text" class="form-control" />
                    </div>
                    <div class="form-group">
                        <label class="text-warning">Check in Date</label>
                        <InputDate @bind-Value="HotelBooking.OrderDetails.CheckInDate" type="date" disabled class="form-control" />
                    </div>
                    <div class="form-group">
                        <label class="text-warning">Check Out Date</label>
                        <InputDate @bind-Value="HotelBooking.OrderDetails.CheckOutDate" type="date" disabled class="form-control" />
                    </div>
                    <div class="form-group">
                        <label class="text-warning">No. of nights</label>
                        <select class="form-control" value="@NoOfNights" @onchange="HandleNoOfNightsChange">
                            @for (var i = 1; i <= 10; i++)
                            {
                                if (i == NoOfNights)
                                {
                                    <option value="@i" selected="selected">@i</option>
                                }
                                else
                                {
                                    <option value="@i">@i</option>
                                }
                            }
                        </select>
                    </div>
                    <div class="form-group">
                        <button type="submit" class="btn btn-success form-control">Checkout Now</button>
                    </div>
                </EditForm>
            </div>
        </div>
    </div>
}

@code {
    // ...

    private async Task HandleNoOfNightsChange(ChangeEventArgs e)
    {
        NoOfNights = Convert.ToInt32(e.Value.ToString());
        HotelBooking.OrderDetails.HotelRoomDTO = await HotelRoomService.GetHotelRoomDetailsAsync(
            Id.Value,
            HotelBooking.OrderDetails.CheckInDate,
            HotelBooking.OrderDetails.CheckInDate.AddDays(NoOfNights));

        HotelBooking.OrderDetails.CheckOutDate = HotelBooking.OrderDetails.CheckInDate.AddDays(NoOfNights);
        HotelBooking.OrderDetails.HotelRoomDTO.TotalDays = NoOfNights;
        HotelBooking.OrderDetails.HotelRoomDTO.TotalAmount =
                NoOfNights * HotelBooking.OrderDetails.HotelRoomDTO.RegularRate;
    }

    private async Task HandleCheckout()
    {
        if (!await HandleValidation())
        {
            return;
        }
    }

    private async Task<bool> HandleValidation()
    {
        if (string.IsNullOrEmpty(HotelBooking.OrderDetails.Name))
        {
            await JsRuntime.ToastrError("Name cannot be empty");
            return false;
        }

        if (string.IsNullOrEmpty(HotelBooking.OrderDetails.Phone))
        {
            await JsRuntime.ToastrError("Phone cannot be empty");
            return false;
        }

        if (string.IsNullOrEmpty(HotelBooking.OrderDetails.Email))
        {
            await JsRuntime.ToastrError("Email cannot be empty");
            return false;
        }
        return true;
    }
}

using System;
using System.Collections.Generic;
using System.Globalization;
using System.Reflection;
using System.Text;


public class PersianCulture : CultureInfo
{
    private readonly Calendar cal;
    private readonly Calendar[] optionals;


    public PersianCulture(): this("FA-IR", true)
    {

    }

    public PersianCulture(string cultureName, bool useUserOverride): base(cultureName, useUserOverride)
    {
        //Temporary Value for cal.
        cal = base.OptionalCalendars[0];

        //populating new list of optional calendars.
        var optionalCalendars = new List<Calendar>();
        optionalCalendars.AddRange(base.OptionalCalendars);
        optionalCalendars.Insert(0, new PersianCalendar());


        Type formatType = typeof(DateTimeFormatInfo);
        Type calendarType = typeof(Calendar);


        PropertyInfo idProperty = calendarType.GetProperty("ID", BindingFlags.Instance | BindingFlags.NonPublic);
        FieldInfo optionalCalendarfield = formatType.GetField("optionalCalendars",
                                                                BindingFlags.Instance | BindingFlags.NonPublic);

        //populating new list of optional calendar ids
        var newOptionalCalendarIDs = new Int32[optionalCalendars.Count];
        for (int i = 0; i < newOptionalCalendarIDs.Length; i++)
            newOptionalCalendarIDs[i] = (Int32)idProperty.GetValue(optionalCalendars[i], null);

        optionalCalendarfield.SetValue(DateTimeFormat, newOptionalCalendarIDs);

        optionals = optionalCalendars.ToArray();
        cal = optionals[0];
        DateTimeFormat.Calendar = optionals[0];

        DateTimeFormat.MonthNames = new[] { "فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی", "بهمن", "اسفند", string.Empty };
        DateTimeFormat.MonthGenitiveNames = new[] { "فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی", "بهمن", "اسفند", string.Empty };
        DateTimeFormat.AbbreviatedMonthNames = new[] { "فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی", "بهمن", "اسفند", string.Empty };
        DateTimeFormat.AbbreviatedMonthGenitiveNames = new[] { "فروردین", "اردیبهشت", "خرداد", "تیر", "مرداد", "شهریور", "مهر", "آبان", "آذر", "دی", "بهمن", "اسفند", string.Empty };

        DateTimeFormat.AbbreviatedDayNames = new string[] { "ی", "د", "س", "چ", "پ", "ج", "ش" };
        DateTimeFormat.ShortestDayNames = new string[] { "ی", "د", "س", "چ", "پ", "ج", "ش" };
        DateTimeFormat.DayNames = new string[] { "یکشنبه", "دوشنبه", "ﺳﻪشنبه", "چهارشنبه", "پنجشنبه", "جمعه", "شنبه" };

        DateTimeFormat.AMDesignator = "ق.ظ";
        DateTimeFormat.PMDesignator = "ب.ظ";

        
        DateTimeFormat.ShortDatePattern = "yyyy/MM/dd";
        DateTimeFormat.LongDatePattern = "yyyy/MM/dd";
             
        DateTimeFormat.SetAllDateTimePatterns(new[] {"yyyy/MM/dd"}, 'd');
        //DateTimeFormat.SetAllDateTimePatterns(new[] {"dddd, dd MMMM yyyy"}, 'D');
        //DateTimeFormat.SetAllDateTimePatterns(new[] {"yyyy MMMM"}, 'y');
        //DateTimeFormat.SetAllDateTimePatterns(new[] {"yyyy MMMM"}, 'Y');
        

    }

    public override Calendar Calendar
    {
        get { return cal; }
    }

    public override Calendar[] OptionalCalendars
    {
        get { return optionals; }
    }
}

۴. دریافت پرس‌و‌جوهای (Queries) مرتب/فیلتر/صفحه‌بندی با اضافه کردن SieveModel به کنترلر (Controller)

[HttpGet]
public JsonResult GetPosts(SieveModel sieveModel) 
{
    var result = _dbContext.Posts;
    result = _sieveProcessor.Apply(sieveModel, result);
    return Json(result.ToList());
}

۵. ارسال درخواست

GET /GetPosts

?sorts=     LikeCount,CommentCount,-created         // sort by likes, then comments, then descendingly by date created 
&filters=   LikeCount>10,Title@=awesome title,      // filter to posts with more than 10 likes, and a title that contains the phrase "awesome title"
&page=      1                                       // get the first page...
&pageSize=  10                                      // ...which contains 10 posts

{
    "Sieve": {
        "CaseSensitive": "boolean: should property names be case-sensitive? Defaults to false",
        "DefaultPageSize": "int number: optional number to fallback to when no page argument is given. Set <=0 to disable paging if no pageSize is specified (default).",
        "MaxPageSize": "int number: maximum allowed page size. Set <=0 to make infinite (default)",
        "ThrowExceptions": "boolean: should Sieve throw exceptions instead of silently failing? Defaults to false"
    }
}

services.Configure<SieveOptions>(Configuration.GetSection("Sieve"));

string greeting = "Hello, C#";

که در این حالت مجموعه‌ای از کاراکترها را ایجاد خواهد کرد:

1. خانه‌های آن یک ضرب پر نمیشوند بلکه به ترتیب، خانه به خانه پر می‌شوند.
2. قبل از انتساب متن باید باید از طول متن مطمئن شویم تا بتوانیم تعداد خانه‌ها را بر اساس آن ایجاد کنیم.
3. همه عملیات آرایه‌ها از پر کردن ابتدای کار گرفته تا هر عملی، نیاز است به صورت دستی صورت بگیرد و تعداد خطوط کد برای هر کاری هم بالا می‌رود.

string str = "abcde";
char ch = str[1]; // ch == 'b'
str[1] = 'a'; // Compilation error!
ch = str[50]; // IndexOutOfRangeException

string a="Hello \"C#\"";
string b="Hello \r\n C#"; //مساوی با اینتر
string c="C:\\a.jpg"; //چاپ خود علامت  \ -مسیردهی

string c=@"C:\a.jpg";// == "C:\\a.jpg"

string source = "Some source";
string assigned = source;

string hel = "Hel";
string hello = "Hello";
string copy = hel + "lo";

string hello = "Hello";
string same = "Hello";

Console.WriteLine(word1.Equals(word2,
    StringComparison.CurrentCultureIgnoreCase));

string score = "sCore";
string scary = "scary";
 
Console.WriteLine(score.CompareTo(scary));
Console.WriteLine(scary.CompareTo(score));
Console.WriteLine(scary.CompareTo(scary));
 
// Console output:
// 1
// -1
// 0

string alpha = "alpha";
string score1 = "sCorE";
string score2 = "score";
 
Console.WriteLine(string.Compare(alpha, score1, false));
Console.WriteLine(string.Compare(score1, score2, false));
Console.WriteLine(string.Compare(score1, score2, true));
Console.WriteLine(string.Compare(score1, score2,
    StringComparison.CurrentCultureIgnoreCase));
// Console output:
// -1
// 1
// 0
// 0

public class User
{
     public int Id { set; get; }
}

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Reflection;
using System.Reflection.Emit;

namespace FastReflectionTests
{
    /// <summary>
    /// کلاسی برای اندازه گیری زمان اجرای عملیات
    /// </summary>
    public class Benchmark : IDisposable
    {
        Stopwatch _watch;
        string _name;

        public static Benchmark Start(string name)
        {
            return new Benchmark(name);
        }

        private Benchmark(string name)
        {
            _name = name;
            _watch = new Stopwatch();
            _watch.Start();
        }

        public void Dispose()
        {
            _watch.Stop();
            Console.WriteLine("{0} Total seconds: {1}"
                               , _name, _watch.Elapsed.TotalSeconds);
        }
    }

    public class User
    {
        public int Id { set; get; }
    }

    class Program
    {
        public static Func<object, object> GetFastGetterFunc(string propertyName, Type ownerType)
        {
            var propertyInfo = ownerType.GetProperty(propertyName, BindingFlags.Instance | BindingFlags.Public);

            if (propertyInfo == null)
                return null;
            
            var getter = ownerType.GetMethod("get_" + propertyInfo.Name,
                                             BindingFlags.Instance | BindingFlags.Public | BindingFlags.FlattenHierarchy);
            if (getter == null)
                return null;

            var dynamicGetterMethod = new DynamicMethod(
                                                name: "_",
                                                returnType: typeof(object),
                                                parameterTypes: new[] { typeof(object) },
                                                owner: propertyInfo.DeclaringType,
                                                skipVisibility: true);
            var il = dynamicGetterMethod.GetILGenerator();

            il.Emit(OpCodes.Ldarg_0); // Load input to stack
            il.Emit(OpCodes.Castclass, propertyInfo.DeclaringType); // Cast to source type
            // نکته مهم در اینجا فراخوانی نهایی متد گت بدون استفاده از ریفلکشن است
            il.Emit(OpCodes.Callvirt, getter); //calls its get method

            if (propertyInfo.PropertyType.IsValueType)
                il.Emit(OpCodes.Box, propertyInfo.PropertyType);//box

            il.Emit(OpCodes.Ret);

            return (Func<object, object>)dynamicGetterMethod.CreateDelegate(typeof(Func<object, object>));
        }


        static void Main(string[] args)
        {
            //تهیه لیستی از داده‌ها جهت آزمایش
            var list = new List<User>();
            for (int i = 0; i < 1000000; i++)
            {
                list.Add(new User { Id = i });
            }

            // دسترسی به اطلاعات لیست به صورت متداول از طریق ریفلکشن معمولی
            var idProperty = typeof(User).GetProperty("Id");
            using (Benchmark.Start("Normal reflection"))
            {
                foreach (var item in list)
                {
                    var id = idProperty.GetValue(item, null);
                }
            }

            // دسترسی از طریق روش سریع دستیابی به اطلاعات خواص
            var fastIdProperty = GetFastGetterFunc("Id", typeof(User));
            using (Benchmark.Start("Fast Property"))
            {
                foreach (var item in list)
                {
                    var id = fastIdProperty(item);
                }
            }
        }
    }
}

 Normal reflection Total seconds: 2.0054177
Fast Property Total seconds: 0.0552056

using System;
using System.Data.Entity;
using System.Data.Entity.Migrations;
using System.Diagnostics;
using System.Linq;

namespace EFGeneral
{
    public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

    public class MyContext : DbContext
    {
        public DbSet<User> Users { get; set; }
    }

    public class Configuration : DbMigrationsConfiguration<MyContext>
    {
        public Configuration()
        {
            AutomaticMigrationsEnabled = true;
            AutomaticMigrationDataLossAllowed = true;
        }

        protected override void Seed(MyContext context)
        {            
            for (int i = 0; i < 21000; i++)
            {
                context.Users.Add(new User { Name = "name " + i });
                if (i % 1000 == 0)
                    context.SaveChanges();
            }
            base.Seed(context);
        }
    }

    public class PerformanceHelper
    {
        public static string RunActionMeasurePerformance(Action action)
        {
            GC.Collect();
            long initMemUsage = Process.GetCurrentProcess().WorkingSet64;

            var stopwatch = new Stopwatch();
            stopwatch.Start();

            action();

            stopwatch.Stop();

            var currentMemUsage = Process.GetCurrentProcess().WorkingSet64;
            var memUsage = currentMemUsage - initMemUsage;
            if (memUsage < 0) memUsage = 0;

            return string.Format("Elapsed time: {0}, Memory Usage: {1:N2} KB", stopwatch.Elapsed, memUsage / 1024);
        }
    }

    public static class Test
    {
        public static void RunTests()
        {
            Database.SetInitializer(new MigrateDatabaseToLatestVersion<MyContext, Configuration>());
            StartDb();            

            for (int i = 0; i < 3; i++)
            {
                Console.WriteLine("\nRun {0}", i + 1);

                var memUsage = PerformanceHelper.RunActionMeasurePerformance(() => LoadWithTracking());
                Console.WriteLine("LoadWithTracking:\n{0}", memUsage);

                memUsage = PerformanceHelper.RunActionMeasurePerformance(() => LoadWithoutTracking());
                Console.WriteLine("LoadWithoutTracking:\n{0}", memUsage);
            }
        }

        private static void StartDb()
        {
            using (var ctx = new MyContext())
            {
                var user = ctx.Users.Find(1);
                if (user != null)
                {
                    // keep the object in memory
                }
            }
        }

        private static void LoadWithTracking()
        {
            using (var ctx = new MyContext())
            {
                var list = ctx.Users.ToList();
                if (list.Any())
                {
                    // keep the list in memory
                }
            }
        }

        private static void LoadWithoutTracking()
        {
            using (var ctx = new MyContext())
            {
                var list = ctx.Users.AsNoTracking().ToList();
                if (list.Any())
                {
                    // keep the list in memory
                }
            }
        }
    }
}

    public interface ICalculator<T>
    {
        T Add(T operand1, T operand2);
    }

    public class Calculator<T> : ICalculator<T>
    {
        public T Add(T operand1, T operand2)
        {
            return operand1 + operand2;
        }
    }

 Operator '+' cannot be applied to operands of type 'T' and 'T'

    public class Calculator2<T>
    {
        public T Sum(List<T> list)
        {
            T sum = 0;
            for (int i = 0; i < list.Count; i++)
                sum += list[i];
            return sum;
        }
    }

    public interface ICalculator<T>
    {
        T Add(T operand1, T operand2);
    }

    public class Int32Calculator : ICalculator<int>
    {
        public int Add(int operand1, int operand2)
        {
            return operand1 + operand2;
        }
    }

    public class AlgorithmLibrary<T> where T : new() 
    {
        private readonly ICalculator<T> _calculator;
        public AlgorithmLibrary(ICalculator<T> calculator)
        {
            _calculator = calculator;
        }

        public T Sum(List<T> items)
        {
            var sum = new T();
            for (var i = 0; i < items.Count; i++)
            {
                sum = _calculator.Add(sum, items[i]);
            }
            return sum;
        }
    }

 var result = new AlgorithmLibrary<int>(new Int32Calculator()).Sum(new List<int> { 1, 2, 3 });

    public class Algorithms<T> where T : new() 
    {
        public T Calculate(Func<T, T, T> add, IEnumerable<T> numbers)
        {
            var sum = new T();
            foreach (var number in numbers)
            {
                sum = add(sum, number);
            }
            return sum;
        }
    }

 var result = new Algorithms<int>().Calculate((a, b) => a + b, new[] { 1, 2, 3 });

    public class Calculator<T> : ICalculator<T>
    {
        public T Add(T operand1, T operand2)
        {
            return (dynamic)operand1 + operand2;
        }
    }

 var test = new Calculator<int>().Add(1, 2);

public T Add(T t1, T t2)
{
    if (typeof(T) == typeof(double))
    {
        var d1 = (double)t1;
        var d2 = (double)t2;
        return (T)(d1 + d2);
    }
    else if (typeof(T) == typeof(int)){
        var i1 = (int)t1;
        var i2 = (int)t2;
        return (T)(i1 + i2);
    }
    else ...
}

using System;
using System.Linq.Expressions;

namespace GenericsArithmetic
{
    public class Solution3
    {
        public T Add<T>(T a, T b)
        {
            var paramA = Expression.Parameter(typeof(T), "a");
            var paramB = Expression.Parameter(typeof(T), "b");

            var body = Expression.Add(paramA, paramB);
            var add = Expression.Lambda<Func<T, T, T>>(body, paramA, paramB).Compile();
            return add(a, b);
        }
    }
}

public static T Sum<T>(this IEnumerable<T> source)
{
    T sum = Operator<T>.Zero;
    foreach (T value in source)
    {
            sum = Operator.Add(sum, value);
    }
    return sum;
}