var num1 = 10;
var num2 = num1;
alert("Num1=" + num1 + ", Num2=" + num2);

num2 = 20;
alert("Num1=" + num1 + ", Num2=" + num2);

num1 = 30;
alert("Num1=" + num1 + ", Num2=" + num2);

var obj1 = new Object();
obj1.num = 10;
var obj2 = obj1;
alert("Obj1.Num=" + obj1.num + ", Obj2.Num=" + obj2.num);

obj2.num = 20;
alert("Obj1.Num=" + obj1.num + ", Obj2.Num=" + obj2.num);

obj1.num = 30;
alert("Obj1.Num=" + obj1.num + ", Obj2.Num=" + obj2.num);

function primitive(a, b) {
a += 100;
b += 200;
alert("a=" + a + ", b=" + b);
}

var x = 300, y = 400;
primitive(x, y);
alert("x=" + x + ", y=" + y);

function reference(obj) {
obj.a += 100;
obj.b += 200;
alert("obj.a=" + obj.a + ", obj.b=" + obj.b);
}

var calc = new Object();
calc.a = 300;
calc.b = 400;

reference(calc);
alert("calc.a=" + calc.a + ", calc.b=" + calc.b);

for (var i = 1; i <= 5; i++) {
var sqr = i * i;
alert(sqr);
}

alert(i);
alert(sqr);

function sqr(num) {
var sum = num * num;
return sum;
}

var n = 4;
alert(sqr(n));
alert(num); // Error: num is not defined
alert(sum); // Error: sum is not defined

var color = "Red";

function setColor() {
color = "Blue";
}

alert(color);
setColor();
alert(color);

var color = "Red";

function getColor() {
var color = "Blue";
return color;
}

alert(color);
alert(getColor());
alert(color);

function sum(a, b) {
c = a + b;
}

sum(20, 30);
alert(c);

namespace Refactoring.Day10.DesignByContract.Before
{
    public class MathMehods
    {
        public double Divide(int dividend, int divisor)
        {
            return dividend / divisor;
        }
    }
}

using System;

namespace Refactoring.Day10.DesignByContract.After
{
    public class MathMehods
    {
        public double Divide(int dividend, int divisor)
        {
            if (divisor == 0)
                throw new ArgumentException("divisor cannot be zero", "divisor");

            return dividend / divisor;
        }
    }
}

using System.Diagnostics.Contracts;

namespace Refactoring.Day10.DesignByContract.After
{
    public class MathMehods
    {
        public double Divide(int dividend, int divisor)
        {
            Contract.Requires(divisor != 0, "divisor cannot be zero");

            return dividend / divisor;
        }
    }
}

• Code Contracts in C#
• Code Contracts in .NET 4
• Introduction to Code Contracts

using System;
using FluentValidation;
using FluentValidation.Validators;

namespace FluentValidationSample.Models
{
    public class LowerThanValidator : PropertyValidator
    {
        public string DependentProperty { get; set; }

        public LowerThanValidator(string dependentProperty) : base($"باید کمتر از {dependentProperty} باشد")
        {
            DependentProperty = dependentProperty;
        }

        protected override bool IsValid(PropertyValidatorContext context)
        {
            if (context.PropertyValue == null)
            {
                return false;
            }

            var typeInfo = context.Instance.GetType();
            var dependentPropertyValue =
                Convert.ToInt32(typeInfo.GetProperty(DependentProperty).GetValue(context.Instance, null));

            return int.Parse(context.PropertyValue.ToString()) < dependentPropertyValue;
        }
    }

    public static class CustomFluentValidationExtensions
    {
        public static IRuleBuilderOptions<T, int> LowerThan<T>(
            this IRuleBuilder<T, int> ruleBuilder, string dependentProperty)
        {
            return ruleBuilder.SetValidator(new LowerThanValidator(dependentProperty));
        }
    }
}

using FluentValidation;
using FluentValidation.AspNetCore;
using FluentValidation.Internal;
using FluentValidation.Resources;
using FluentValidation.Validators;
using Microsoft.AspNetCore.Mvc.ModelBinding.Validation;

namespace FluentValidationSample.Models
{
    public class LowerThanClientValidator : ClientValidatorBase
    {
        private LowerThanValidator LowerThanValidator
        {
            get { return (LowerThanValidator)Validator; }
        }

        public LowerThanClientValidator(PropertyRule rule, IPropertyValidator validator) :
            base(rule, validator)
        {
        }

        public override void AddValidation(ClientModelValidationContext context)
        {
            MergeAttribute(context.Attributes, "data-val", "true");
            MergeAttribute(context.Attributes, "data-val-LowerThan", GetErrorMessage(context));
            MergeAttribute(context.Attributes, "data-val-LowerThan-dependentproperty", LowerThanValidator.DependentProperty);
        }

        private string GetErrorMessage(ClientModelValidationContext context)
        {
            var formatter = ValidatorOptions.MessageFormatterFactory().AppendPropertyName(Rule.GetDisplayName());
            string messageTemplate;
            try
            {
                messageTemplate = Validator.Options.ErrorMessageSource.GetString(null);
            }
            catch (FluentValidationMessageFormatException)
            {
                messageTemplate = ValidatorOptions.LanguageManager.GetStringForValidator<NotEmptyValidator>();
            }
            return formatter.BuildMessage(messageTemplate);
        }
    }
}

<input dir="rtl" type="number"
 data-val="true"
 data-val-lowerthan="باید کمتر از Age باشد"
 data-val-lowerthan-dependentproperty="Age"
 data-val-required="'سابقه کار' must not be empty."
 id="Experience"
 name="Experience"
 value="">

    public class UserModel
    {
        [Display(Name = "نام کاربری")]
        public string Username { get; set; }

        [Display(Name = "سن")]
        public int Age { get; set; }

        [Display(Name = "سابقه کار")]
        public int Experience { get; set; }
    }

    public class UserValidator : AbstractValidator<UserModel>
    {
        public UserValidator()
        {
            RuleFor(x => x.Username).NotNull();
            RuleFor(x => x.Age).NotNull();
            RuleFor(x => x.Experience).LowerThan(nameof(UserModel.Age)).NotNull();
        }
    }

namespace FluentValidationSample.Web
{
    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews().AddFluentValidation(
                fv =>
                {
                    fv.RegisterValidatorsFromAssembly(Assembly.GetExecutingAssembly());
                    fv.RegisterValidatorsFromAssemblyContaining<RegisterModelValidator>();
                    fv.RunDefaultMvcValidationAfterFluentValidationExecutes = false;

                    fv.ConfigureClientsideValidation(clientSideValidation =>
                    {
                        clientSideValidation.Add(
                            validatorType: typeof(LowerThanValidator),
                            factory: (context, rule, validator) => new LowerThanClientValidator(rule, validator));
                    });
                }
            );
        }

<script src="~/lib/jquery/dist/jquery.min.js"></script>
<script src="~/lib/bootstrap/dist/js/bootstrap.bundle.min.js"></script>
<script src="~/lib/jquery-validation/dist/jquery.validate.js"></script>
<script src="~/lib/jquery-validation-unobtrusive/jquery.validate.unobtrusive.js"></script>
<script src="~/js/site.js" asp-append-version="true"></script>

$.validator.unobtrusive.adapters.add('LowerThan', ['dependentproperty'], function (options) {
    options.rules['LowerThan'] = {
        dependentproperty: options.params['dependentproperty']
    };
    options.messages['LowerThan'] = options.message;
});

$.validator.addMethod('LowerThan', function (value, element, parameters) {      
    var dependentProperty = '#' + parameters['dependentproperty'];
    var dependentControl = $(dependentProperty);
    if (dependentControl) {
        var targetvalue = dependentControl.val();
        if (parseInt(targetvalue) > parseInt(value)) {
            return true;
        }
        return false;
    }
    return true;
});

@using FluentValidationSample.Models
@model UserModel
@{
    ViewData["Title"] = "Home Page";
}
<div dir="rtl">
    <form asp-controller="Home"
          asp-action="RegisterUser"
          method="post">
        <fieldset class="form-group">
        <legend>ثبت نام</legend>
            <div class="form-group row">
                <label asp-for="Username" class="col-md-2 col-form-label text-md-left"></label>
                <div class="col-md-10">
                    <input dir="rtl" asp-for="Username" class="form-control" />
                    <span asp-validation-for="Username" class="text-danger"></span>
                </div>
            </div>
            <div class="form-group row">
                <label asp-for="Age" class="col-md-2 col-form-label text-md-left"></label>
                <div class="col-md-10">
                    <input dir="rtl" asp-for="Age" class="form-control" />
                    <span asp-validation-for="Age" class="text-danger"></span>
                </div>
            </div>
            <div class="form-group row">
                <label asp-for="Experience" class="col-md-2 col-form-label text-md-left"></label>
                <div class="col-md-10">
                    <input dir="rtl" asp-for="Experience" class="form-control" />
                    <span asp-validation-for="Experience" class="text-danger"></span>
                </div>
            </div>

            <div class="form-group row">
                <label class="col-md-2 col-form-label text-md-left"></label>
                <div class="col-md-10 text-md-right">
                    <button type="submit" class="btn btn-info col-md-2">ارسال</button>
                </div>
            </div>
        </fieldset>
    </form>
</div>

   [DataContract]
    public class Employee
    {
        [DataMember]
        public string Name { get; set; }

        [DataMember]
        public Employee Manager { get; set; }
    }

[DataContract]
    public class Department
    {
        [DataMember]
        public string DeptName { get; set; }

        [DataMember]
        public List<Employee> Staff { get; set; }
    }

  [ServiceContract]
    public interface IDepartmentService
    {
        [OperationContract]
        Department GetOneDepartment();
    }

public class DepartmentService : IDepartmentService
    {
        public Department GetOneDepartment()
        {
            List<Employee> listOfEmployees = new List<Employee>();

              var masoud = new Employee() { Name = "Masoud" };
              var saeed = new Employee() { Name = "Saeed", Manager = masoud };
              var peyman = new Employee() { Name = "Peyman", Manager = saeed };
              var mostafa = new Employee() { Name = "Mostafa", Manager = saeed };

              return new Department() { DeptName = "IT", Staff = new List<Employee>() { masoud, saeed, peyman, mostafa } };
        }
    }

 class Program
    {
        static void Main( string[] args )
        {
            DepartmentServiceClient client = new DepartmentServiceClient();

            var result = client.GetOneDepartment();
            WriteDataToFile( result );

            Console.ReadKey();
        }

        private static void WriteDataToFile( Department data )
        {
            DataContractSerializer dcs = new DataContractSerializer( typeof( Department ) );
            var ms = new MemoryStream();
            dcs.WriteObject( ms, data );
            ms.Seek( 0, SeekOrigin.Begin );
            var sr = new StreamReader( ms );
            var xml = sr.ReadToEnd();
            string filePath = @"d:\\data.xml";
            if ( !File.Exists( filePath ) )
            {
                File.Create( filePath );
            }         
                using ( TextWriter writer = new StreamWriter( filePath ) )
                {
                    writer.Write( xml );
                }                      
        }

<Department xmlns="http://schemas.datacontract.org/2004/07/Service" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <Name>IT</Name>
  <Staff>
    <Employee>
      <Manager i:nil="true"/>
      <Name>Masoud</Name>
    </Employee>
    <Employee>
      <Manager>
        <Manager i:nil="true"/>
        <Name>Masoud</Name>
      </Manager>
      <Name>Saeed</Name>
    </Employee>
    <Employee>
      <Manager>
        <Manager>
          <Manager i:nil="true"/>
          <Name>Masoud</Name>
        </Manager>
        <Name>Saeed</Name>
      </Manager>
      <Name>Peyman</Name>
    </Employee>
    <Employee>
      <Manager>
        <Manager>
          <Manager i:nil="true"/>
          <Name>Masoud</Name>
        </Manager>
        <Name>Saeed</Name>
      </Manager>
      <Name>Mostafa</Name>
    </Employee>
  </Staff>
</Department>

<Department xmlns="http://schemas.datacontract.org/2004/07/Service" xmlns:i="http://www.w3.org/2001/XMLSchema-instance">
  <Name>IT</Name>
  <Staff>
    <Employee z:Id="i1" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/">
      <Manager i:nil="true"/>
      <Name>Masoud</Name>
    </Employee>
    <Employee z:Id="i2" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/">
      <Manager z:Ref="i1"/>
      <Name>Saeed</Name>
    </Employee>
    <Employee z:Id="i3" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/">
      <Manager z:Ref="i2"/>
      <Name>Peyman</Name>
    </Employee>
    <Employee z:Id="i4" xmlns:z="http://schemas.microsoft.com/2003/10/Serialization/">
      <Manager z:Ref="i2"/>
      <Name>Mostafa</Name>
    </Employee>
  </Staff>
</Department>

public static void Write(int age, string name, string homeTown)

Write(age: 20, "User 1", homeTown: "Tehran");

Named argument specifications must appear after all fixed arguments have been specified.

Write(age: 20, name: "User 1", "T1");
Write(age: 21, "User 2", homeTown: "T2");
Write(age: 22, "User 3", "T3");
Write(23, name: "User 4", "T4");

C:\Program Files\Microsoft ASP.NET\ASP.NET Web Pages\v2.0\Assemblies
C:\Program Files\Microsoft ASP.NET\ASP.NET MVC 4\Assemblies

{E53F8FEA-EAE0-44A6-8774-FFD645390401}

{E3E379DF-F4C6-4180-9B81-6769533ABE47}

System.Web.Mvc, Version=3.0.0.0
System.Web.WebPages, Version=1.0.0.0
System.Web.Helpers, Version=1.0.0.0
System.Web.WebPages.Razor, Version=1.0.0.0

System.Web.Mvc, Version=4.0.0.0
System.Web.WebPages, Version=2.0.0.0
System.Web.Helpers, Version=2.0.0.0
System.Web.WebPages.Razor, Version=2.0.0.0

C:\Program Files\Microsoft ASP.NET\ASP.NET Web Pages\v1.0\Assemblies
C:\Program Files\Microsoft ASP.NET\ASP.NET MVC 3\Assemblies

C:\Program Files\Microsoft ASP.NET\ASP.NET Web Pages\v2.0\Assemblies
C:\Program Files\Microsoft ASP.NET\ASP.NET MVC 4\Assemblies

<appSettings>
  <add key="webpages:Version" value="2.0.0.0" />
  <add key="PreserveLoginUrl" value="true" />
</appSettings>

<configuration>
  <!--... elements deleted for clarity ...-->
 
  <runtime>
    <assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Helpers" 
             publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.Mvc" 
             publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0-3.0.0.0" newVersion="4.0.0.0"/>
      </dependentAssembly>
      <dependentAssembly>
        <assemblyIdentity name="System.Web.WebPages" 
             publicKeyToken="31bf3856ad364e35" />
        <bindingRedirect oldVersion="1.0.0.0" newVersion="2.0.0.0"/>
      </dependentAssembly>
    </assemblyBinding>
  </runtime>
</configuration>

    <pages>
      <namespaces>
        <add namespace="System.Web.Optimization" />
      </namespaces>
    </pages>

[ValidateAntiForgeryToken(Salt = "data123")]

using System.Collections.Generic;
using System.IO;
using System.Web;
using System.Web.Optimization;

namespace Common.WebToolkit
{
    /// <summary>
    /// A custom bundle orderer (IBundleOrderer) that will ensure bundles are 
    /// included in the order you register them.
    /// </summary>
    public class AsIsBundleOrderer : IBundleOrderer
    {
        public IEnumerable<FileInfo> OrderFiles(BundleContext context, IEnumerable<FileInfo> files)
        {
            return files;
        }
    }

    public static class BundleConfig
    {
        private static void addBundle(string virtualPath, bool isCss, params string[] files)
        {
            BundleTable.EnableOptimizations = true;

            var existing = BundleTable.Bundles.GetBundleFor(virtualPath);
            if (existing != null)
                return;

            var newBundle = isCss ? new Bundle(virtualPath, new CssMinify()) : new Bundle(virtualPath, new JsMinify());
            newBundle.Orderer = new AsIsBundleOrderer();

            foreach (var file in files)
                newBundle.Include(file);

            BundleTable.Bundles.Add(newBundle);
        }

        public static IHtmlString AddScripts(string virtualPath, params string[] files)
        {
            addBundle(virtualPath, false, files);
            return Scripts.Render(virtualPath);
        }

        public static IHtmlString AddStyles(string virtualPath, params string[] files)
        {
            addBundle(virtualPath, true, files);
            return Styles.Render(virtualPath);
        }

        public static IHtmlString AddScriptUrl(string virtualPath, params string[] files)
        {
            addBundle(virtualPath, false, files);
            return Scripts.Url(virtualPath);
        }

        public static IHtmlString AddStyleUrl(string virtualPath, params string[] files)
        {
            addBundle(virtualPath, true, files);
            return Styles.Url(virtualPath);
        }
    }
}

@using Common.WebToolkit

<link href="@BundleConfig.AddStyleUrl("~/Content/blueprint/print", "~/Content/blueprint/print.css")" rel="stylesheet" type="text/css" media="print"/>

@BundleConfig.AddScripts("~/Scripts/js",
                            "~/Scripts/jquery-1.8.0.min.js",
                            "~/Scripts/jquery.unobtrusive-ajax.min.js",
                            "~/Scripts/jquery.validate.min.js")

@BundleConfig.AddStyles("~/Content/css",
                            "~/Content/Site.css",
                            "~/Content/buttons.css")

http://site/Content/blueprint/print?v=hash

@BundleConfig.AddStyles("~/Content/noty/css",
                                "~/Content/noty/jquery.noty.css",
                                "~/Content/noty/noty_theme_default.css")