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
                }
            }
        }
    }
}

• WeakMap و WeakSet فاقد پراپرتی‌های size, entries, values و متد foreach هستند.
  
• WeakMap همچنین فاقد keys است.
  

    public class Project
    {
        public int Id { set; get; }
        public string Name { set; get; }

        public virtual ICollection<ProjectIssue> ProjectIssues { set; get; }
    }

    public class ProjectIssue
    {
        public int Id { set; get; }
        public string Body { set; get; }

        [ForeignKey("ProjectStatusId")]
        public virtual ProjectIssueStatus ProjectIssueStatus { set; get; }
        public int ProjectStatusId { set; get; }

        [ForeignKey("ProjectId")]
        public virtual Project Project { set; get; }
        public int ProjectId { set; get; }
    }

    public class ProjectIssueStatus
    {
        public int Id { set; get; }
        public string Name { set; get; }

        public virtual ICollection<ProjectIssue> ProjectIssues { set; get; }
    }

    public class MyContext : DbContext
    {
        public DbSet<ProjectIssueStatus> ProjectStatus { get; set; }
        public DbSet<ProjectIssue> ProjectIssues { get; set; }
        public DbSet<Project> Projects { get; set; }
    }

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

        protected override void Seed(MyContext context)
        {
            var project1 = new Project { Name = "پروژه جدید" };
            context.Projects.Add(project1);

            var stat1 = new ProjectIssueStatus { Name = "درحال انجام" };
            var stat2 = new ProjectIssueStatus { Name = "انجام شد" };
            context.ProjectStatus.Add(stat1);
            context.ProjectStatus.Add(stat2);

            var issue1 = new ProjectIssue
            {
                Body = "تغییر قلم گزارش",
                ProjectIssueStatus = stat1,
                Project = project1
            };
            var issue2 = new ProjectIssue
            {
                Body = "تغییر لوگوی گزارش",
                ProjectIssueStatus = stat1,
                Project = project1
            };
            context.ProjectIssues.Add(issue1);
            context.ProjectIssues.Add(issue2);

            base.Seed(context);
        }
    }

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

            using (var ctx = new MyContext())
            {
                var projectId = 1;
                var list = ctx.ProjectStatus.Select(x => new
                                                    {
                                                        Id = x.Id,
                                                        Name = x.Name,
                                                        Count = x.ProjectIssues.Count(p => p.ProjectId == projectId)
                                                    }).ToList();
                foreach (var item in list)
                    Console.WriteLine("{0}:{1}",item.Name, item.Count);                
            }
        }
    }

SELECT [Project1].[Id] AS [Id],
       [Project1].[Name] AS [Name],
       [Project1].[C1] AS [C1]
FROM   (
           SELECT [Extent1].[Id] AS [Id],
                  [Extent1].[Name] AS [Name],
                  (
                      SELECT COUNT(1) AS [A1]
                      FROM   [dbo].[ProjectIssues] AS [Extent2]
                      WHERE  ([Extent1].[Id] = [Extent2].[ProjectStatusId])
                             AND ([Extent2].[ProjectId] = 1 /*@p__linq__0*/)
                  ) AS [C1]
           FROM   [dbo].[ProjectIssueStatus] AS [Extent1]
       ) AS [Project1]

@page "/demoHotel"

        <div class="col-12">
            <h4 class="text-info">Hotel Rooms</h4>
            <span>Rooms Selected - @SelectedRooms</span>
        </div>
        @foreach (var room in Rooms)
        {
            <IndividualRoom Room="room"></IndividualRoom>
        }

@code{

    int SelectedRooms;

    void RoomSelectionCounterChanged(bool isRoomSelected)
    {
        if (isRoomSelected)
        {
            SelectedRooms++;
        }
        else
        {
            SelectedRooms--;
        }
    }
    // ...
}

<input type="checkbox" @onchange="RoomCheckBoxSelectionChanged" />

@code
{
    //...

    [Parameter]
    public EventCallback<bool> OnRoomCheckBoxSelection { get; set; }

    async Task RoomCheckBoxSelectionChanged(ChangeEventArgs e)
    {
        await OnRoomCheckBoxSelection.InvokeAsync((bool)e.Value);
    }
}

@foreach (var room in Rooms)
{
    <IndividualRoom OnRoomCheckBoxSelection="RoomSelectionCounterChanged" Room="room"></IndividualRoom>
}

<div class="bg-light border p-2 col-5 offset-1 mt-2"
    @onclick="args => AmenitySelectionChanged(args, Amenity.Name)">
    <h4 class="text-secondary">Amenity - @Amenity.Id</h4>
    @Amenity.Name<br />
    @Amenity.Description<br />
</div>

@code
{
    [Parameter]
    public BlazorAmenity Amenity { get; set; }

    [Parameter]
    public EventCallback<string> OnAmenitySelection { get; set; }

    protected async Task AmenitySelectionChanged(MouseEventArgs e, string name)
    {
        await OnAmenitySelection.InvokeAsync(name);
    }
}

@onclick="args => AmenitySelectionChanged(args, Amenity.Name)"

@page "/demoHotel"

    @foreach (var amenity in AmenitiesList)
    {
      <IndividualAmenity OnAmenitySelection="AmenitySelectionChanged" Amenity="amenity"></IndividualAmenity>
    }

    <div class="col-12">
        <p class="text-secondary"> Selected Amenity : @SelectedAmenity </p>
    </div>

@code{

    string SelectedAmenity = "";

    void AmenitySelectionChanged(string amenity)
    {
        SelectedAmenity = amenity;
    }
}