public SelectList(IEnumerable items, string dataValueField, string dataTextField, Object selectedValue)

// in controller
ViewBag.Countries = new SelectList(countries.GetCountries(), "id", "countryName", "82" /* selected id */);

// in view
@Html.DropDownListFor(model => model.CountryId, (IEnumerable<SelectListItem>)ViewBag.Countries, new { @class = "form-control" })

//Person.cs
namespace DependencyInjectionForDummies
{
   class Person
   {
       public string Name { get; set; }
   }
}

//Car.cs
using System;
using System.Collections.Generic;

namespace DependencyInjectionForDummies
{
   class Car
   {
       List<Person> _passengers = new List<Person>();

       public void AddPassenger(Person p)
       {
           _passengers.Add(p);
           Console.WriteLine("{0} added!", p.Name);
       }

       public void Drive()
       {
           foreach (var passenger in _passengers)
               Console.WriteLine("Driving {0} ...!", passenger.Name);
       }
   }
}

//Driver.cs
using System.Collections.Generic;

namespace DependencyInjectionForDummies
{
   class Driver
   {
       private Car _myCar = new Car();

       public void DriveToMarket(IList<Person> passengers)
       {
           foreach (var passenger in passengers)
               _myCar.AddPassenger(passenger);

           _myCar.Drive();
       }
   }
}

//Program.cs
using System.Collections.Generic;
using System;

namespace DependencyInjectionForDummies
{
   class Program
   {
       static void Main(string[] args)
       {
           new Driver().DriveToMarket(
               new List<Person>
               {
                   new Person{ Name="Ali" },
                   new Person{ Name="Vahid" }
               });

           Console.WriteLine("Press a key ...");
           Console.ReadKey();
       }
   }
}

//ICar.cs
using System;

namespace DependencyInjectionForDummies
{
   interface ICar
   {
       void AddPassenger(Person p);
       void Drive();
   }
}

//Car.cs
using System;
using System.Collections.Generic;

namespace DependencyInjectionForDummies
{
   class Car : ICar
   {
       //همانند قسمت قبل
   }
}

//Van.cs
using System;
using System.Collections.Generic;

namespace DependencyInjectionForDummies
{
   class Van : ICar
   {
       List<Person> _passengers = new List<Person>();

       public void AddPassenger(Person p)
       {
           _passengers.Add(p);
           Console.WriteLine("{0} added!", p.Name);
       }

       public void Drive()
       {
           foreach (var passenger in _passengers)
               Console.WriteLine("Driving {0} ...!", passenger.Name);
       }
   }
}

//Driver.cs
using System.Collections.Generic;

namespace DependencyInjectionForDummies
{
   class Driver
   {
       private ICar _myCar;

       public Driver(ICar myCar)
       {
           _myCar = myCar;
       }

       public void DriveToMarket(IList<Person> passengers)
       {
           foreach (var passenger in passengers)
               _myCar.AddPassenger(passenger);

           _myCar.Drive();
       }
   }
}

//Program.cs
using System.Collections.Generic;
using System;

namespace DependencyInjectionForDummies
{
   class Program
   {
       static void Main(string[] args)
       {
           Driver driver = new Driver(new Van());
           driver.DriveToMarket(
               new List<Person>
               {
                   new Person{ Name="Ali" },
                   new Person{ Name="Vahid" }
               });

           Console.WriteLine("Press a key ...");
           Console.ReadKey();
       }
   }
}

Bag=IList
Set=Iesi.Collections.ISet
List=IList
Map=IDictionary

using System.Collections.Generic;

namespace Test1.Model12
{
   public class User
   {
       public virtual int Id { set; get; }
       public virtual string Name { get; set; }
       public virtual IDictionary<string, string> Preferences { get; set; }
   }
}

using FluentNHibernate.Automapping;
using FluentNHibernate.Automapping.Alterations;

namespace Test1.Model12
{
   public class UserMapping : IAutoMappingOverride<User>
   {
       public void Override(AutoMapping<User> mapping)
       {
           mapping.Id(x => x.Id);
           mapping.HasMany(x => x.Preferences)
               .AsMap<string>("FieldKey")
               .Element("FieldValue", x => x.Type<string>().Length(500));
       }
   }
}

create table "User" (
      Id INT IDENTITY NOT NULL,
      Name NVARCHAR(255) null,
      primary key (Id)
   )

create table Preferences (
      User_id INT not null,
      FieldValue NVARCHAR(500) null,
      FieldKey NVARCHAR(255) not null,
      primary key (User_id, FieldKey)
   )

alter table Preferences
       add constraint FKD6CB18523B1FD789
       foreign key (User_id)
       references "User"

using System.Collections.Generic;

namespace Test1.Model13
{
   public class User
   {
       public virtual int Id { get; set; }
       public virtual string Name { get; set; }
       public virtual IDictionary<string, Property> Properties { get; set; }
   }

   public class Property
   {
       public virtual int Id { get; set; }
       public virtual string Name { get; set; }
       public virtual string Value { get; set; }
       public virtual User User { get; set; }
   }
}

using FluentNHibernate.Automapping;
using FluentNHibernate.Automapping.Alterations;

namespace Test1.Model13
{
   public class UserMapping : IAutoMappingOverride<User>
   {
       public void Override(AutoMapping<User> mapping)
       {
           mapping.Id(x => x.Id);
           mapping.HasMany<Property>(x => x.Properties)
               .AsMap<string>("FieldKey")
               .Component(x => x.Map(c => c.Id));
       }
   }
}

create table "Property" (
      Id INT IDENTITY NOT NULL,
      Name NVARCHAR(255) null,
      Value NVARCHAR(255) null,
      User_id INT null,
      primary key (Id)
   )

create table "User" (
      Id INT IDENTITY NOT NULL,
      Name NVARCHAR(255) null,
      primary key (Id)
   )

create table Properties (
      User_id INT not null,
      Id INT null,
      FieldKey NVARCHAR(255) not null,
      primary key (User_id, FieldKey)
   )

alter table "Property"
       add constraint FKF9F4D85A3B1FD7A2
       foreign key (User_id)
       references "User"

alter table Properties
       add constraint FK63646D853B1FD7A2
       foreign key (User_id)
       references "User"

using System;
using System.Collections.Generic;

namespace Test1.Model14
{
   public class FormData
   {
       public virtual int Id { get; set; }
       public virtual DateTime? DateTime { get; set; }
       public virtual IDictionary<FormField, string> FormPropertyValues { get; set; }
   }

   public class FormField
   {
       public virtual int Id { get; set; }
       public virtual string Name { get; set; }
   }
}

using FluentNHibernate.Automapping;
using FluentNHibernate.Automapping.Alterations;

namespace Test1.Model14
{
   public class FormDataMapping : IAutoMappingOverride<FormData>
   {
       public void Override(AutoMapping<FormData> mapping)
       {
           mapping.Id(x => x.Id);
           mapping.HasMany<FormField>(x => x.FormPropertyValues)
                  .AsEntityMap("FieldId")
                  .Element("FieldValue", x => x.Type<string>().Length(500))
                  .Cascade.All();
       }
   }
}

create table "FormData" (
      Id INT IDENTITY NOT NULL,
      DateTime DATETIME null,
      primary key (Id)
   )

create table FormPropertyValues (
      FormData_id INT not null,
      FieldValue NVARCHAR(500) null,
      FieldId INT not null,
      primary key (FormData_id, FieldId)
   )

create table "FormField" (
      Id INT IDENTITY NOT NULL,
      Name NVARCHAR(255) null,
      primary key (Id)
   )

alter table FormPropertyValues
       add constraint FKB807B9C090849E
       foreign key (FormData_id)
       references "FormData"

alter table FormPropertyValues
       add constraint FKB807B97165898A
       foreign key (FieldId)
       references "FormField"

public class Service
{
   public virtual int Id { get; set; }
   public virtual string Name { get; set; }
   public virtual IList<ServiceFormField> Fields { get; set; }
   public virtual IList<ServiceFormData> Forms { get; set; }
}

public class ServiceFormField
{
   public virtual int Id { get; set; }
   public virtual string Name { get; set; }
   public virtual bool IsRequired { get; set; }
   public virtual Service Service { get; set; }
}

public class ServiceFormData
{
   public virtual int Id { get; set; }
   public virtual IDictionary<ServiceFormField, string> FormPropertyValues { get; set; }       
   public virtual DateTime? DateTime { get; set; }
   public virtual Service Service { get; set; }
}

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="AjaxTest.aspx.cs" Inherits="testWebForms87.AjaxTest" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>jQuery Ajax Text</title>

<script src="jquery.min.js" type="text/javascript"></script>
<script type="text/javascript">
    $(document).ready(function() {
        $("#<%= TextBox1.ClientID %>").blur(function(event) {
            $.ajax({
                type: "POST",
                url: "AjaxTest.aspx/IsUserAvailable",
                data: "{'username': '" + $('#<%= TextBox1.ClientID %>').val() + "'}",
                contentType: "application/json; charset=utf-8",
                dataType: "json",
                success: function(msg) {
                    $('#valid').html("<img src='ajaxImages/waiting.gif' alt='لطفا کمی تامل کنید'>");
                    var delay = function() {
                        AjaxSucceeded(msg);
                    };

                    setTimeout(delay, 2000); //remove this
                },
                error: AjaxFailed
            });
        });
    });
    function AjaxSucceeded(result) {
        if (result.d == true)
            $('#msg').html("<img src='ajaxImages/available.gif' alt='نام کاربری درخواستی موجود است'>");
        else
            $('#msg').html("<img src='ajaxImages/taken.gif' alt='متاسفانه نام کاربری مورد نظر پیشتر دریافت شده‌است'>");
    }
    function AjaxFailed(result) {
        alert(result.status + ' ' + result.statusText);
    }
</script>

</head>
<body>
<form id="form1" runat="server">
<div>
    user name:
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
    <span id="msg"></span>
    <br />
    pass:
    <asp:TextBox ID="TextBox2" TextMode="Password" runat="server"></asp:TextBox>
</div>
<!-- preload -->
<div style="display: none">
    <img src="ajaxImages/available.gif" alt="available" />
    <img src="ajaxImages/taken.gif" alt="taken" />
    <img src="ajaxImages/waiting.gif" alt="waiting" />
</div>
</form>
</body>
</html>

using System;
using System.Web.Services;

namespace testWebForms87
{
public partial class AjaxTest : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }

    [WebMethod]
    public static bool IsUserAvailable(string username)
    {
        // این مورد را با خواندن اطلاعات از دیتابیس می‌شود تعویض کرد
        return username != "test";
    }
}
}

type: "POST"

url: "AjaxTest.aspx/IsUserAvailable"

data: "{'username': '" + $('#<%= TextBox1.ClientID %>').val() + "'}",

contentType: "application/json; charset=utf-8",

dataType: "json",

<xx yy="nn"></xx>

{ "xx": {"yy":"nn"} }

success: function(msg)

error: AjaxFailed

class="modified valid form-control"

class="modified invalid form-control"

EditContext = new EditContext(Model);
EditContext.SetFieldCssClassProvider(new BootstrapFieldCssClassProvider());

using System;
using System.Linq;
using Microsoft.AspNetCore.Components.Forms;

namespace BlazorComponents
{
    /// <summary>
    /// Supplies CSS class names for form fields to represent their validation state or other state information from an EditContext.
    /// </summary>
    public class BootstrapFieldCssClassProvider : FieldCssClassProvider
    {
        /// <summary>
        /// Gets a string that indicates the status of the specified field as a CSS class.
        /// </summary>
        public override string GetFieldCssClass(EditContext editContext, in FieldIdentifier fieldIdentifier)
        {
            if (editContext == null)
            {
                throw new ArgumentNullException(nameof(editContext));
            }

            var isValid = !editContext.GetValidationMessages(fieldIdentifier).Any();

            if (editContext.IsModified(fieldIdentifier))
            {
                return isValid ? "is-valid" : "is-invalid";
            }
            return isValid ? "" : "is-invalid";
        }
    }
}