public class Page
    {
        public virtual int Id { get; set; }
        public virtual string Title { get; set; }
        public virtual DateTime? CreatedDate { get; set; }
        public virtual DateTime? ModifiedDate { get; set; }
        public virtual string Body { get; set; }
        public virtual string Keyword { get; set; }
        public virtual string Description { get; set; }
        public virtual string Status { get; set; }
        public virtual bool? CommentStatus { get; set; }
        public virtual int? Order { get; set; }
        public virtual User User { get; set; }
        public virtual User EditedByUser { get; set; }
        public virtual ICollection<Comment> Comments { get; set; }
        public virtual int? ParentId { get; set; }
        public virtual Page Parent { get; set; }
        public virtual ICollection<Page> Children { get; set; }
    }

this._pages.ToList().Where(page => page.Parent == null).ToList();

SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[Title] AS [Title], 
[Extent1].[CreatedDate] AS [CreatedDate], 
[Extent1].[ModifiedDate] AS [ModifiedDate], 
[Extent1].[Body] AS [Body], 
[Extent1].[Keyword] AS [Keyword], 
[Extent1].[Description] AS [Description], 
[Extent1].[Status] AS [Status], 
[Extent1].[CommentStatus] AS [CommentStatus], 
[Extent1].[Order] AS [Order], 
[Extent1].[ParentId] AS [ParentId], 
[Extent2].[Id] AS [Id1], 
[Extent2].[Title] AS [Title1], 
[Extent2].[CreatedDate] AS [CreatedDate1], 
[Extent2].[ModifiedDate] AS [ModifiedDate1], 
[Extent2].[Body] AS [Body1], 
[Extent2].[Keyword] AS [Keyword1], 
[Extent2].[Description] AS [Description1], 
[Extent2].[Status] AS [Status1], 
[Extent2].[CommentStatus] AS [CommentStatus1], 
[Extent2].[Order] AS [Order1], 
[Extent2].[ParentId] AS [ParentId1], 
[Extent2].[User_Id] AS [User_Id], 
[Extent2].[EditedByUser_Id] AS [EditedByUser_Id], 
[Extent1].[User_Id] AS [User_Id1], 
[Extent1].[EditedByUser_Id] AS [EditedByUser_Id1]
FROM  [dbo].[Pages] AS [Extent1]
LEFT OUTER JOIN [dbo].[Pages] AS [Extent2] ON [Extent1].[ParentId] = [Extent2].[Id

static void Main(string[] args)
{
    int Add(int a, int b)
    {
        return a + b;
    }
 
    Console.WriteLine(Add(3, 4)); 
}

public class PersonWithPrivateMethod
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override string ToString()
    {
        string ageSuffix = GenerateAgeSuffix(Age);
        return $"{Name} is {Age} year{ageSuffix} old";
    }

    private string GenerateAgeSuffix(int age)
    {
        return age > 1 ? "s" : "";
    }
}

public class PersonWithLocalFuncDelegate
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override string ToString()
    {
        Func<int, string> generateAgeSuffix = age => age > 1 ? "s" : "";
        return $"{Name} is {Age} year{generateAgeSuffix(Age)} old";
    }
}

public class PersonWithLocalFunction
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override string ToString()
    {
        return $"{Name} is {Age} year{GenerateAgeSuffix(Age)} old";
        // Define a local function:
        string GenerateAgeSuffix(int age)
        {
            return age > 1 ? "s" : "";
        }
    }
}

public class PersonWithLocalFunctionEnclosing
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override string ToString()
    {
        return $"{Name} is {Age} year{GenerateAgeSuffix()} old";
        // Define a local function:
        string GenerateAgeSuffix()
        {
            return Age > 1 ? "s" : "";
        }
    }
}

public class PersonWithLocalFunctionExpressionBodied
{
    public string Name { get; set; }
    public int Age { get; set; }

    public override string ToString()
    {
        return $"{Name} is {Age} year{GenerateAgeSuffix(Age)} old";
        // Define a local function:
        string GenerateAgeSuffix(int age) => age > 1 ? "s" : "";
    }
}

public class LocalFunctionsTest
{
    public void PassAnonFunctionToMethod()
    {
        var p = new SimplePerson
        {
            Name = "Name1",
            Age = 42
        };
        OutputSimplePerson(p, GenerateAgeSuffix);
        string GenerateAgeSuffix(int age) => age > 1 ? "s" : "";
    }
 
    private void OutputSimplePerson(SimplePerson person, Func<int, string> suffixFunction)
    {
        Output.WriteLine(
        $"{person.Name} is {person.Age} year{suffixFunction(person.Age)} old");
    }
}

public class CustomProfile
    {
        [Required(ErrorMessage="*")]
        [StringLength(50)]
        [System.Web.Mvc.Remote(action: "CheckUserName",
                                       controller: "User",
                                       HttpMethod = "POST",
                                       ErrorMessage = "این نام کاربری وجود دارد")]
        public string Username{ get; set; }
        [Required(ErrorMessage = "*")]
        public string Password{ get; set; }
        [Required(ErrorMessage = "*")]
        public string FirstName{ get; set; }
        [Required(ErrorMessage = "*")]
        public string LastName{ get; set; }
        
        [Required(ErrorMessage = "*")]
        [StringLength(10, ErrorMessage = "کدملی باید 10 رقم باشد")]
        public string NationalCode { get; set; }
        [Required(ErrorMessage = "*")]
        public string Address { get; set; }

        [RegularExpression(@"\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*",
                           ErrorMessage = "آدرس ایمیل معتبر نیست")]
        [System.Web.Mvc.Remote(action: "CheckEmail",
                                       controller: "User",
                                       AdditionalFields = "Username",
                                       HttpMethod = "POST",
                                       ErrorMessage = "این ایمیل وجود دارد")]
        public string Email{ get; set; }

        [StringLength(11, ErrorMessage = "تلفن باید 11 رقم باشد")]
        public string PhoneNo{ get; set; }

        [StringLength(11, ErrorMessage = "موبایل باید 11 رقم باشد")]
        public string MobileNo{ get; set; }
        
        
        public string[] Roles{ get; set; }
        
        public string LastActivityDate{ get; set; }
        public string LastLoginDate { get; set; }
        public string CreationDate { get; set; }
        public bool IsLockedOut{ get; set; }
    }

@model Sama.Models.CustomProfile
@{
    ViewBag.Title = "Create";
    Layout = "~/Views/Shared/_Layout.cshtml";
    
}
<script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script>
<script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>
@using (Html.BeginForm(actionName: "Create", controllerName: "User"))
    {
        @Html.ValidationSummary(true)
     
        <fieldset>
            <legend>کاربر جدید</legend>
            <div>
                <table>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.Username, "نام کاربری")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.EditorFor(model => model.Username)
                                @Html.ValidationMessageFor(model => model.Username)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.Password, "کلمه عبور")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.PasswordFor(model => model.Password)
                                @Html.ValidationMessageFor(model => model.Password)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.FirstName, "نام")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.EditorFor(model => model.FirstName)
                                @Html.ValidationMessageFor(model => model.FirstName)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.LastName, "نام خانوادگی")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.EditorFor(model => model.LastName)
                                @Html.ValidationMessageFor(model => model.LastName)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.NationalCode, "کد ملی")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.EditorFor(model => model.NationalCode)
                                @Html.ValidationMessageFor(model => model.NationalCode)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.Email, "ایمیل")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.EditorFor(model => model.Email)
                                @Html.ValidationMessageFor(model => model.Email)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.PhoneNo, "تلفن")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.EditorFor(model => model.PhoneNo)
                                @Html.ValidationMessageFor(model => model.PhoneNo)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.MobileNo, "موبایل")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.EditorFor(model => model.MobileNo)
                                @Html.ValidationMessageFor(model => model.MobileNo)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            <div>
                                @Html.LabelFor(model => model.Address, "آدرس")
                            </div>
                        </td>
                        <td>
                            <div>
                                @Html.TextAreaFor(model => model.Address, 5, 30, null)
                                @Html.ValidationMessageFor(model => model.Address)
                            </div>
                        </td>
                    </tr>
                    <tr>
                        <td>
                            نقش‌ها </td>
                        <td>
                            @Helper.CheckBoxList("Roles", (List<SelectListItem>)ViewBag.Roles)
                        </td>
                    </tr>
                    <tr>
                        <td>
                        </td>
                        <td>
                            <input type="submit" value="ذخیره" class="btn btn-primary" />
                        </td>
                    </tr>
                </table>
            </div>
        </fieldset>
    
    }

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

        [StringLength(450)]
        public string Name { get; set; }

        public int? ParentId { get; set; }

        public virtual Category Parent { get; set; }

        public virtual ICollection<Category> Children { get; set; }
    }

    public class CategoryConfiguration : IEntityTypeConfiguration<Category>
    {
        public void Configure(EntityTypeBuilder<Category> builder)
        {
            builder.HasIndex(c => c.ParentId);

            builder.HasOne(c => c.Parent)
                   .WithMany(c => c.Children)
                   .HasForeignKey(c => c.ParentId);
        }
    }

    public class CompanyModel
    {
        public int Id { get; set; }
        public string CompanyName { get; set; }
        public string CompanyAbbr { get; set; }

        public Product Product { set; get; }
    }

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

var data = PropertyExtensions.PropertyName<CompanyModel>(x => x.Product.Id);

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;

namespace PropertyExtensionsApp
{
    public class PropertyHelper : ExpressionVisitor
    {
        private Stack<string> _stack;
        public string GetNestedPropertyPath(Expression expression)
        {
            _stack = new Stack<string>();
            Visit(expression);
            return _stack.Aggregate((s1, s2) => s1 + "." + s2);
        }

        protected override Expression VisitMember(MemberExpression expression)
        {
            if (_stack != null)
                _stack.Push(expression.Member.Name);
            return base.VisitMember(expression);
        }

        public string GetNestedPropertyName<TEntity>(Expression<Func<TEntity, object>> expression)
        {
            return GetNestedPropertyPath(expression);
        }
    }
}

var name = new PropertyHelper().GetNestedPropertyName<CompanyModel>(x => x.Product.Id);

public class UserModel
{
    [MaxLength(200)]
    [Display(Name = "Full name")]
    [Required]
    public string Name { get; set; }
}

public class UserModalViewModel
{
    public UserModel Model { get; set; }
    public bool IsAdmin { get; set; }
    public IReadonlyList<lookupitem> Roles { get; set; }
}

public class Magazine
{
  public int MagazineId { get; set; }
  public string Name { get; set; }
  public string Publisher { get; set; }

  public List<Article> Articles { get; set; }
}

public class Article
{
  public int ArticleId { get; set; }
  public string Title { get; set; }
  public DateTime PublishDate { get;  set; }

  public int MagazineId { get; set; }

  public Author Author { get; set; }
  public int? AuthorId { get; set; }
}

public class Author
{
  public int AuthorId { get; set; }
  public string Name { get; set; }

  public List<Article> Articles { get; set; }
}

protected override void OnModelCreating (ModelBuilder modelBuilder)
{
   modelBuilder.Entity<Magazine>().HasData(new Magazine { MagazineId = 1, Name = "DNT Magazine" });
}

migrationBuilder.InsertData(
  table: "Magazines",
  columns: new[] { "MagazineId", "Name", "Publisher" },
  values: new object[] { 1, "DNT Magazine", null });

set IDENTITY_INSERT ON
INSERT INTO "Magazines" ("MagazineId", "Name", "Publisher") VALUES (1, 'DNT Magazine', NULL);

modelBuilder.Entity<Magazine>()
           .HasData(new Magazine{ MagazineId=2, Name="This Mag" },
                    new Magazine{ MagazineId=3, Name="That Mag" }
           );

modelBuilder.Entity<Magazine>().Property(m=>m.Publisher).IsRequired();

 "The seed entity for entity type 'Magazine' cannot be added because there was no value provided for the required property 'Publisher'."

public Magazine(string name, string publisher)
{
  Name=name;
  Publisher=publisher;
}

modelBuilder.Entity<Magazine>().HasData(new Magazine("DNT Magazine", "1105 Media"));

modelBuilder.Entity<Magazine>().HasData(new {MagazineId=1, Name="DNT Mag", Publisher="1105 Media"});

migrationBuilder.InsertData(
                table: "Magazines",
                columns: new[] { "MagazineId", "Name", "Publisher" },
                values: new object[] { 1, "DNT Mag", "1105 Media" });

public class Magazine
{
  public Magazine(string name, string publisher)
  {
    Name=name;
    Publisher=publisher;
    MagazineId=Guid.NewGuid();
  }

  public Guid MagazineId { get; private set; }
  public string Name { get; private set; }
  public string Publisher { get; private set; }
  public List<Article> Articles { get; set; }
}

modelBuilder.Entity<Magazine>().HasData(new Magazine("DNT Mag", "1105 Media");

var mag1=new {MagazineId= new Guid("0483b59c-f7f8-4b21-b1df-5149fb57984e"),  Name="DNT Mag", Publisher="1105 Media"};
modelBuilder.Entity<Magazine>().HasData(mag1);

modelBuilder.Entity<Article>().HasData(new Article { ArticleId = 1, MagazineId = 1, Title = "EF Core 2.1 Query Types"});

var mag1=new {MagazineId= new Guid("0483b59c-f7f8-4b21-b1df-5149fb57984e"),  Name="DNT Mag", Publisher="1105 Media"};
modelBuilder.Entity<Magazine>().HasData(mag1);

public class Publisher
{
  public string Name { get; set; }
  public int YearFounded { get; set; }
}

public class Magazine
{ 
  public int MagazineId { get;  set; }
  public string Name { get;  set; }
  public Publisher Publisher { get;  set; }
  public List<Article> Articles { get; set; }
}

modelBuilder.Entity<Magazine>().HasData (new Magazine { MagazineId = 1, Name = "DNT Magazine" });
modelBuilder.Entity<Magazine>().OwnsOne (m => m.Publisher)
   .HasData (new { Name = "1105 Media", YearFounded = 2006, MagazineId=1 });

migrationBuilder.InsertData(
  table: "Magazines",
  columns: new[] { "MagazineId", "Name", "Publisher_Name", "Publisher_YearFounded" },
  values: new object[] { 1, "DNT Magazine", "1105 Media", 2006 });

namespace EFCoreMultipleDb.Web
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            applyPendingMigrations(app);
// ...
        }

        private static void applyPendingMigrations(IApplicationBuilder app)
        {
            var scopeFactory = app.ApplicationServices.GetRequiredService<IServiceScopeFactory>();
            using (var scope = scopeFactory.CreateScope())
            {
                var uow = scope.ServiceProvider.GetService<IUnitOfWork>();
                uow.Migrate();
            }
        }
    }
}

namespace EFCoreMultipleDb.DataLayer.SQLite.Context
{
    public class SQLiteDbContext : DbContext, IUnitOfWork
    {
    // ... 

        public void Migrate()
        {
            this.Database.Migrate();
        }
    }
}

public static void Main(string[] args)
{
   var host = BuildWebHost(args);
   using (var scope = host.Services.CreateScope())
   {
       var context = scope.ServiceProvider.GetRequiredService<yourDBContext>();
       context.Database.Migrate();
   }
   host.Run();
}

var json = JsonConvert.SerializeObject(obj, new JsonSerializerSettings
{
   ContractResolver = new CamelCasePropertyNamesContractResolver()
});

using Newtonsoft.Json;

namespace JsonNetTests
{
    public enum Color
    {
        Red,
        Green,
        Blue,
        White
    }

    public class Item
    {
        public string Name { set; get; }
        public Color Color { set; get; }
    }

    public class EnumTests
    {
        public string GetJson()
        {
            var item = new Item
            {
                Name = "Item 1",
                Color = Color.Blue 
            };

            return JsonConvert.SerializeObject(item, Formatting.Indented);
        }
    }
}

{
  "Name": "Item 1",
  "Color": 2
}

  [JsonConverter(typeof(StringEnumConverter))]
  public Color Color { set; get; }

return JsonConvert.SerializeObject(item, new JsonSerializerSettings
{
   Formatting = Formatting.Indented,
   Converters = { new StringEnumConverter() }
});

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

        public virtual ICollection<Product> Products { get; set; }

        public Category()
        {
            Products = new List<Product>();
        }
    }

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

        public virtual Category Category { get; set; }
    }

using System.Collections.Generic;
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;

namespace JsonNetTests
{
    public class SelfReferencingLoops
    {
        public string GetJson()
        {
            var category = new Category
            {
                Id = 1,
                Name = "Category 1"
            };
            var product = new Product
            {
                Id = 1,
                Name = "Product 1"
            };

            category.Products.Add(product);
            product.Category = category;

            return JsonConvert.SerializeObject(category, new JsonSerializerSettings
            {
                Formatting = Formatting.Indented,
                Converters = { new StringEnumConverter() }
            });
        }
    }
}

 An unhandled exception of type 'Newtonsoft.Json.JsonSerializationException' occurred in Newtonsoft.Json.dll
Additional information: Self referencing loop detected for property 'Category' with type 'JsonNetTests.Category'. Path 'Products[0]'.

return JsonConvert.SerializeObject(category, new JsonSerializerSettings
{
   Formatting = Formatting.Indented,
   ReferenceLoopHandling = ReferenceLoopHandling.Ignore,
   Converters = { new StringEnumConverter() }
});

return JsonConvert.SerializeObject(category, new JsonSerializerSettings
{
   Formatting = Formatting.Indented,
   PreserveReferencesHandling = PreserveReferencesHandling.Objects,
   Converters = { new StringEnumConverter() }
});

{
  "$id": "1",
  "Id": 1,
  "Name": "Category 1",
  "Products": [
    {
      "$id": "2",
      "Id": 1,
      "Name": "Product 1",
      "Category": {
        "$ref": "1"
      }
    }
  ]
}