public static int Add(in int number1, in int number2)
{
   number1 = 5; // Cannot assign to variable 'in int' because it is a readonly variable
   return number1 + number2;
}

<ItemGroup>
     <PackageReference Include="BenchmarkDotNet" Version="0.10.12" />
</ItemGroup>

using BenchmarkDotNet.Attributes;

namespace CS72Tests
{
    public struct Input
    {
        public decimal Number1;
        public decimal Number2;
    }

    [MemoryDiagnoser]
    public class InBenchmarking
    {
        const int loops = 50000000;
        Input inputInstance = new Input();

        [Benchmark(Baseline = true)]
        public decimal RunNormalLoop_Pass_By_Value()
        {
            decimal result = 0M;
            for (int i = 0; i < loops; i++)
            {
                result = Run(inputInstance);
            }
            return result;
        }

        [Benchmark]
        public decimal RunInLoop_Pass_By_Reference()
        {
            decimal result = 0M;
            for (int i = 0; i < loops; i++)
            {
                result = RunIn(in inputInstance);
            }
            return result;
        }

        public decimal Run(Input input)
        {
            return input.Number1;
        }

        public decimal RunIn(in Input input)
        {
            return input.Number1;
        }
    }
}

static void Main(string[] args)
{
    var summary = BenchmarkRunner.Run<InBenchmarking>();

                      Method |      Mean |    Error |   StdDev | Scaled | Allocated |
---------------------------- |----------:|---------:|---------:|-------:|----------:|
 RunNormalLoop_Pass_By_Value | 280.04 ms | 2.219 ms | 1.733 ms |   1.00 |       0 B |
 RunInLoop_Pass_By_Reference |  91.75 ms | 1.733 ms | 1.780 ms |   0.33 |       0 B |

    public static class Factorial
    {
        public static int Calculate(in this int num)
        {
            int result = 1;
            for (int i = num; i > 1; i--)
                result *= i;

            return result;
        }
    }

int num = 3;
Console.WriteLine($"(in num) -> {Factorial.Calculate(in num)}");
Console.WriteLine($"(num) -> {Factorial.Calculate(num)}");
Console.WriteLine($"num. -> {num.Calculate()}");

(in num) -> 6
(num) -> 6
num. -> 6

    public class CX
    {
        public void A(Input a)
        {
            Console.WriteLine("int a");
        }

        public void A(in Input a)
        {
            Console.WriteLine("in int a");
        }
    }

    public class Y
    {
        public void Test()
        {
            var inputInstance = new Input();
            var cx = new CX();
            cx.A(inputInstance); // The call is ambiguous between the following methods or properties: 'CX.A(Input)' and 'CX.A(in Input)'
        }
    }

public IEnumerable<int> B(in int a) // Iterators cannot have ref or out parameters
{
   Console.WriteLine("in int a");
   yield return 1;
}

public async Task C(in int a) // Async methods cannot have ref or out parameters
{
   await Task.Delay(1000);
}

using System;

namespace CS72Tests
{
    struct MyStruct
    {
        public int MyValue { get; set; }

        public void UpdateMyValue(int value)
        {
            MyValue = value;
        }
    }

    public static class TestInStructs
    {
        public static void Run()
        {
            var myStruct = new MyStruct();
            myStruct.UpdateMyValue(1);

            UpdateMyValue(myStruct);

            Console.WriteLine(myStruct.MyValue);
        }

        static void UpdateMyValue(in MyStruct myStruct)
        {
            myStruct.UpdateMyValue(5);
        }
    }
}

static void UpdateMyValue(in MyStruct myStruct)
{
   myStruct.MyValue = 5; // Cannot assign to a member of variable 'in MyStruct' because it is a readonly variable
   myStruct.UpdateMyValue(5);
}

The Find method on DbSet uses the primary key value to attempt to find an entity tracked by the context.
If the entity is not found in the context then a query will be sent to the database to find the entity there.
Null is returned if the entity is not found in the context or in the database.

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

namespace EF_General.Models.Ex21
{
    public abstract class BaseEntity
    {
        public int Id { set; get; }
    }

    public class Factor : BaseEntity
    {
        public int TotalPrice { set; get; }
    }

    public class MyContext : DbContext
    {
        public DbSet<Factor> Factors { get; set; }

        public MyContext() { }
        public MyContext(bool withTracking)
        {
            if (withTracking)
                return;

            this.Configuration.ProxyCreationEnabled = false;
            this.Configuration.LazyLoadingEnabled = false;
            this.Configuration.AutoDetectChangesEnabled = false;
        }

        public void CustomUpdate<T>(T entity) where T : BaseEntity
        {
            if (entity == null)
                throw new ArgumentException("Cannot add a null entity.");


            var entry = this.Entry<T>(entity);
            if (entry.State != EntityState.Detached)
                return;

            /*var set = this.Set<T>(); // این‌ها اضافی است
            //متد فایند اگر اینجا باشه حتما به بانک اطلاعاتی رجوع می‌کنه در حالت منقطع از زمینه و در یک حلقه به روز رسانی کارآیی مطلوبی نخواهد داشت
            T attachedEntity = set.Find(entity.Id);
            if (attachedEntity != null)
            {
                var attachedEntry = this.Entry(attachedEntity);
                attachedEntry.CurrentValues.SetValues(entity);
            }
            else
            {*/
            entry.State = EntityState.Modified;
            //}
        }
    }

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

        protected override void Seed(MyContext context)
        {
            if (!context.Factors.Any())
            {
                for (int i = 0; i < 20; i++)
                {
                    context.Factors.Add(new Factor { TotalPrice = i });
                }
            }
            base.Seed(context);
        }
    }

    public class Performance
    {
        public TimeSpan ListDisabledTracking { set; get; }
        public TimeSpan ListNormal { set; get; }
        public TimeSpan DetachedEntityDisabledTracking { set; get; }
        public TimeSpan DetachedEntityNormal { set; get; }
    }

    public static class Test
    {
        public static void RunTests()
        {
            startDb();

            var results = new List<Performance>();
            var runs = 20;
            for (int i = 0; i < runs; i++)
            {
                Console.WriteLine("\nRun {0}", i + 1);

                var tsListDisabledTracking = PerformanceHelper.RunActionMeasurePerformance(() => updateListTotalPriceDisabledTracking());
                var tsListNormal = PerformanceHelper.RunActionMeasurePerformance(() => updateListTotalPriceNormal());
                var tsDetachedEntityDisabledTracking = PerformanceHelper.RunActionMeasurePerformance(() => updateDetachedEntityTotalPriceDisabledTracking());
                var tsDetachedEntityNormal = PerformanceHelper.RunActionMeasurePerformance(() => updateDetachedEntityTotalPriceNormal());
                results.Add(new Performance
                {
                    ListDisabledTracking = tsListDisabledTracking,
                    ListNormal = tsListNormal,
                    DetachedEntityDisabledTracking = tsDetachedEntityDisabledTracking,
                    DetachedEntityNormal = tsDetachedEntityNormal
                });
            }

            var detachedEntityDisabledTrackingAvg = results.Average(x => x.DetachedEntityDisabledTracking.TotalMilliseconds);
            Console.WriteLine("detachedEntityDisabledTrackingAvg: {0} ms.", detachedEntityDisabledTrackingAvg);

            var detachedEntityNormalAvg = results.Average(x => x.DetachedEntityNormal.TotalMilliseconds);
            Console.WriteLine("detachedEntityNormalAvg: {0} ms.", detachedEntityNormalAvg);

            var listDisabledTrackingAvg = results.Average(x => x.ListDisabledTracking.TotalMilliseconds);
            Console.WriteLine("listDisabledTrackingAvg: {0} ms.", listDisabledTrackingAvg);

            var listNormalAvg = results.Average(x => x.ListNormal.TotalMilliseconds);
            Console.WriteLine("listNormalAvg: {0} ms.", listNormalAvg);
        }

        private static void updateDetachedEntityTotalPriceNormal()
        {
            using (var context = new MyContext(withTracking: true))
            {
                var detachedEntity = new Factor { Id = 1, TotalPrice = 10 };

                var attachedEntity = context.Factors.Find(detachedEntity.Id);
                if (attachedEntity != null)
                {
                    attachedEntity.TotalPrice = 100;

                    context.SaveChanges();
                }
            }
        }

        private static void updateDetachedEntityTotalPriceDisabledTracking()
        {
            using (var context = new MyContext(withTracking: false))
            {
                var detachedEntity = new Factor { Id = 2, TotalPrice = 10 };
                detachedEntity.TotalPrice = 200;

                context.CustomUpdate(detachedEntity); // custom update with change tracking disabled.
                context.SaveChanges();
            }
        }

        private static void updateListTotalPriceNormal()
        {
            using (var context = new MyContext(withTracking: true))
            {
                foreach (var item in context.Factors)
                {
                    item.TotalPrice += 10; // normal update with change tracking enabled.
                }
                context.SaveChanges();
            }
        }

        private static void updateListTotalPriceDisabledTracking()
        {
            using (var context = new MyContext(withTracking: false))
            {
                foreach (var item in context.Factors)
                {
                    item.TotalPrice += 10;
                    //نیازی به این دو سطر نیست
                    //context.ChangeTracker.DetectChanges();  // هربار باید محاسبه صورت گیرد در غیراینصورت وضعیت تغییر نیافته گزارش می‌شود
                    //context.CustomUpdate(item); // custom update with change tracking disabled.
                }
                context.ChangeTracker.DetectChanges();  // در غیراینصورت وضعیت تغییر نیافته گزارش می‌شود
                context.SaveChanges();
            }
        }

        private static void startDb()
        {
            Database.SetInitializer(new MigrateDatabaseToLatestVersion<MyContext, Configuration>());
            // Forces initialization of database on model changes.
            using (var context = new MyContext())
            {
                context.Database.Initialize(force: true);
            }
        }
    }

    public class PerformanceHelper
    {
        public static TimeSpan RunActionMeasurePerformance(Action action)
        {
            var stopwatch = new Stopwatch();
            stopwatch.Start();

            action();

            stopwatch.Stop();
            return stopwatch.Elapsed;
        }
    }
}

 detachedEntityDisabledTrackingAvg: 22.32089 ms.
detachedEntityNormalAvg: 54.546815 ms.
listDisabledTrackingAvg: 413.615445 ms.
listNormalAvg: 393.194625 ms.

 CREATE TABLE [Geo](
[id] [int] IDENTITY(1,1) NOT NULL,
[Location] [geography] NULL
)

 insert into Geo( Location , long, lat ) values
( geography::STGeomFromText ('POINT(-121.527200 45.712113)', 4326))

using System.Data.Entity.Spatial;

namespace EFGeoTests.Models
{
    public class GeoLocation
    {
        public int Id { get; set; }
        public DbGeography Location { get; set; }
        public string Name { get; set; }
        public string Type { get; set; }

        public override string ToString()
        {
            return string.Format("Name:{0}, Location:{1}", Name, Location);
        }
    }
}

using System;
using System.Data.Entity;
using EFGeoTests.Models;

namespace EFGeoTests.Config
{
    public class MyContext : DbContext
    {
        public DbSet<GeoLocation> GeoLocations { get; set; }

        public MyContext()
            : base("Connection1")
        {
            this.Database.Log = sql => Console.Write(sql);
        }
    }
}

   private static DbGeography createPoint(double longitude, double latitude,  int coordinateSystemId = 4326)
  {
       var text = string.Format(CultureInfo.InvariantCulture.NumberFormat,"POINT({0} {1})", longitude, latitude);
       return DbGeography.PointFromText(text, coordinateSystemId);
  }

GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]]

        /// <summary>
        /// Gets the current shape in the collection
        /// </summary>
        public Shape Current
        {
            get 
            {
                if (_disposed) throw new ObjectDisposedException("Shapefile");
                if (!_opened) throw new InvalidOperationException("Shapefile not open.");
               
                // get the metadata
                StringDictionary metadata = null;
                if (!RawMetadataOnly)
                {
                    metadata = new StringDictionary();
                    for (int i = 0; i < _dbReader.FieldCount; i++)
                    {
                        string value = _dbReader.GetValue(i).ToString();
                        if (_dbReader.GetDataTypeName(i) == "DBTYPE_WVARCHAR")
                        {
                            // برای نمایش متون فارسی نیاز است
                            value = Encoding.UTF8.GetString(Encoding.GetEncoding(720).GetBytes(value));
                        }
                        metadata.Add(_dbReader.GetName(i),
                            value);
                    }
                }

using System.Collections.Generic;
using System.Linq;
using Catfood.Shapefile;

namespace EFGeoTests
{
    public class MapPoint
    {
        public Dictionary<string, string> Metadata { set; get; }
        public double X { set; get; }
        public double Y { set; get; }
    }

    public static class ShapeReader
    {
        public static IList<MapPoint> ReadShapeFile(string path)
        {
            var results = new List<MapPoint>();

            using (var shapefile = new Shapefile(path))
            {
                foreach (var shape in shapefile)
                {
                    if (shape.Type != ShapeType.Point)
                        continue;

                    var shapePoint = shape as ShapePoint;
                    if (shapePoint == null)
                        continue;


                     var metadataNames = shape.GetMetadataNames();
                    if(!metadataNames.Any())
                        continue;

                    var metadata = new Dictionary<string, string>();
                    foreach (var metadataName in metadataNames)
                    {
                        metadata.Add(metadataName,shape.GetMetadata(metadataName));
                    }

                    results.Add(new MapPoint
                    {
                        Metadata = metadata,
                        X = shapePoint.Point.X,
                        Y = shapePoint.Point.Y
                    });
                }
            }

            return results;
        }
    }
}

            var points = ShapeReader.ReadShapeFile("IranShapeFiles\\places.shp");
            using (var context = new MyContext())
            {
                context.Configuration.AutoDetectChangesEnabled = false;
                context.Configuration.ProxyCreationEnabled = false;
                context.Configuration.ValidateOnSaveEnabled = false;

                if (context.GeoLocations.Any())
                    return;

                foreach (var point in points)
                {
                    context.GeoLocations.Add(new GeoLocation
                    {
                        Name = point.Metadata["name"],
                        Type = point.Metadata["type"],
                        Location = createPoint(point.X, point.Y)
                    });
                }

                context.SaveChanges();
            }

            var tehran = createPoint(51.4179604, 35.6884243);

            using (var context = new MyContext())
            {
                // find any locations within 5 kilometers ordered by distance
                var locations = context.GeoLocations
                    .Where(loc => loc.Location.Distance(tehran) < 5000)
                    .OrderBy(loc => loc.Location.Distance(tehran))
                    .ToList();

                foreach (var location in locations)
                {
                    Console.WriteLine(location.Name);
                }
            }

            var tehran = createPoint(51.4179604, 35.6884243);
            using (var context = new MyContext())
            {
                // find any locations within 5 kilometers ordered by distance
                var tehranLocation = context.GeoLocations.FirstOrDefault(loc => loc.Location.SpatialEquals(tehran));
                if (tehranLocation != null)
                {
                    Console.WriteLine(tehranLocation.Type);
                }
            }

            try
            {
                using (WebSession mywebsession = WebCore.CreateWebSession(
new WebPreferences() { CustomCSS = "::-webkit-scrollbar { visibility: hidden; }" }))
                {
                    using (var view = WebCore.CreateWebView(1240, 1000, mywebsession))
                    {
                        view.Source = new Uri("https://site.com/");

                        bool finishedLoading = false;
                        view.LoadingFrameComplete += (s, e) =>
                        {
                            if (e.IsMainFrame)
                                finishedLoading = true;
                        };

                        while (!finishedLoading)
                        {
                            Thread.Sleep(100);
                            WebCore.Update();
                        }

                        using (var surface = (BitmapSurface)view.Surface)
                        {
                            surface.SaveToJPEG("result.jpg");
                        }
                    }
                }
            }
            finally
            {
                WebCore.Shutdown();
            }

 System.InvalidOperationException: You are attempting to re-initialize the WebCore.
The WebCore must only be initialized once per process and must be shut down only when the process exits.

 System.AccessViolationException: Attempted to read or write protected memory.
This is often an indication that other memory is corrupt. at Awesomium.Core.NativeMethods.WebCore_CreateWebView_1(HandleRef jarg1, Int32 jarg2, Int32 jarg3, HandleRef jarg4)

using System;
using System.Collections.Concurrent;
using System.IO;
using System.Threading;
using System.Web;
using Awesomium.Core;

namespace AwesomiumWebModule
{
    public class AwesomiumModule : IHttpModule
    {
        private static readonly Thread WorkerThread = new Thread(awesomiumWorker);
        private static readonly ConcurrentQueue<AwesomiumRequest> TaskQueue = new ConcurrentQueue<AwesomiumRequest>();
        private static bool _isRunning = true;

        static AwesomiumModule()
        {
            WorkerThread.Start();
        }       

        private static void awesomiumWorker()
        {
            while (_isRunning)
            {
                if (TaskQueue.Count != 0)
                {
                    AwesomiumRequest outRequest;
                    if (TaskQueue.TryDequeue(out outRequest))
                    {
                        var img = AwesomiumThumbnail.FetchWebPageThumbnail(outRequest);
                        File.WriteAllBytes(outRequest.SavePath, img);
                        Thread.Sleep(500);
                    }
                }
                Thread.Sleep(5);
            }
        }

        public void Dispose()
        {
            _isRunning = false;
            WebCore.Shutdown();
        }

        public void Init(HttpApplication context)
        {
            context.EndRequest += endRequest;
        }

        static void endRequest(object sender, EventArgs e)
        {
            var url = HttpContext.Current.Items[Constants.AwesomiumRequest] as AwesomiumRequest;
            if (url!=null)
            {
                TaskQueue.Enqueue(url);
            }
        }
    }
}

<?xml version="1.0"?>
<configuration>
  <system.web>
    <compilation debug="true" targetFramework="4.0" />
    <httpModules>
      <add name="AwesomiumWebModule" type="AwesomiumWebModule.AwesomiumModule"/>
    </httpModules>
  </system.web>

  <system.webServer>
    <validation validateIntegratedModeConfiguration="false"/>
    <modules>
      <add name="AwesomiumWebModule" type="AwesomiumWebModule.AwesomiumModule"/>
    </modules>
  </system.webServer>
</configuration>

        protected void btnStart_Click(object sender, EventArgs e)
        {
            var host = new Uri(txtUrl.Text).Host;
            HttpContext.Current.Items.Add(Constants.AwesomiumRequest, new AwesomiumRequest
            {
                Url = txtUrl.Text,
                SavePath = Path.Combine(HttpRuntime.AppDomainAppPath, "App_Data\\Thumbnails\\" + host + ".jpg"),
                TempDir = Path.Combine(HttpRuntime.AppDomainAppPath, "App_Data\\Temp")
            });
            lblInfo.Text = "Please wait. Your request will be served shortly.";
        }

namespace SplittingTableSample.DomainClasses
{
    public class Post
    {
        public virtual int Id { get; set; }
        public virtual string Title { get; set; }
        public virtual DateTime CreatedDate { get; set; }
        public virtual string  Body { get; set; }
        public virtual byte[] Image { get; set; }
    }
}

            using (var context = new MyDbContext())
            {
                var post = context.Posts.Find(1);
            }

exec sp_executesql N'SELECT TOP (2) 
[Extent1].[Id] AS [Id], 
[Extent1].[Title] AS [Title], 
[Extent1].[CreatedDate] AS [CreatedDate], 
[Extent1].[Body] AS [Body], 
[Extent1].[Image] AS [Image]
FROM [dbo].[Posts] AS [Extent1]
WHERE [Extent1].[Id] = @p0',N'@p0 int',@p0=1

namespace SplittingTableSample.DomainClasses
{
    public class Post
    {
        public virtual int Id { get; set; }
        public virtual string Title { get; set; }
        public virtual DateTime CreatedDate { get; set; }
        public virtual PostMetaData PostMetaData { get; set; }
    }
}
namespace SplittingTableSample.DomainClasses
{
    public class PostMetaData
    {
        public virtual int PostId { get; set; }
        public virtual string Body { get; set; }
        public virtual byte[] Image { get; set; }
        public virtual Post Post { get; set; }
    }
}

namespace SplittingTableSample.DomainClasses
{
    public class PostMetaDataConfig : EntityTypeConfiguration<PostMetaData>
    {
        public PostMetaDataConfig()
        {
            HasKey(x => x.PostId);
            HasRequired(x => x.Post).WithRequiredDependent(x => x.PostMetaData);
        }
    }
}

var post = context.Posts.Find(1);

exec sp_executesql N'SELECT TOP (2) 
[Extent1].[Id] AS [Id], 
[Extent1].[Title] AS [Title], 
[Extent1].[CreatedDate] AS [CreatedDate]
FROM [dbo].[Posts] AS [Extent1]
WHERE [Extent1].[Id] = @p0',N'@p0 int',@p0=1

namespace SplittingTableSample.DomainClasses
{
    public class PostConfig : EntityTypeConfiguration<Post>
    {
        public PostConfig()
        {
            ToTable("Posts");
        }
    }
}
namespace SplittingTableSample.DomainClasses
{
    public class PostMetaDataConfig : EntityTypeConfiguration<PostMetaData>
    {
        public PostMetaDataConfig()
        {
            ToTable("Posts");
            HasKey(x => x.PostId);
            HasRequired(x => x.Post).WithRequiredDependent(x => x.PostMetaData);
        }
    }
}

var post = context.Posts.Find(1);
Console.WriteLine(post.PostMetaData.Body);

exec sp_executesql N'SELECT TOP (2) 
[Extent1].[Id] AS [Id], 
[Extent1].[Title] AS [Title], 
[Extent1].[CreatedDate] AS [CreatedDate]
FROM [dbo].[Posts] AS [Extent1]
WHERE [Extent1].[Id] = @p0',N'@p0 int',@p0=1

exec sp_executesql N'SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[Body] AS [Body], 
[Extent1].[Image] AS [Image]
FROM [dbo].[Posts] AS [Extent1]
WHERE [Extent1].[Id] = @EntityKeyValue1',N'@EntityKeyValue1 int',@EntityKeyValue1=1

var post = context.Posts.Include(x => x.PostMetaData).SingleOrDefault(x => x.Id == 1);

SELECT 
[Limit1].[Id] AS [Id], 
[Limit1].[Title] AS [Title], 
[Limit1].[CreatedDate] AS [CreatedDate], 
[Extent2].[Id] AS [Id1], 
[Extent2].[Body] AS [Body], 
[Extent2].[Image] AS [Image]
FROM   (SELECT TOP (2) [Extent1].[Id] AS [Id], [Extent1].[Title] AS [Title], [Extent1].[CreatedDate] AS [CreatedDate]
FROM [dbo].[Posts] AS [Extent1]
WHERE 1 = [Extent1].[Id] ) AS [Limit1]
LEFT OUTER JOIN [dbo].[Posts] AS [Extent2] ON [Limit1].[Id] = [Extent2].[Id]

_identityVerifier.Initialize();
var isValidIdentity = _identityVerifier.Validate(
     application.Applicant.Name, application.Applicant.Age, application.Applicant.Address);

namespace Loans.Tests
{
    [TestClass]
    public class LoanApplicationProcessorShould
    {
        [TestMethod]
        public void Accept()
        {
            var product = new LoanProduct {Id = 99, ProductName = "Loan", InterestRate = 5.25m};
            var amount = new LoanAmount {CurrencyCode = "Rial", Principal = 2_000_000_0};
            var applicant =
                new Applicant {Id = 1, Name = "User 1", Age = 25, Address = "This place", Salary = 1_500_000_0};
            var application = new LoanApplication {Id = 42, Product = product, Amount = amount, Applicant = applicant};

            var mockIdentityVerifier = new Mock<IIdentityVerifier>();
            mockIdentityVerifier.Setup(x => x.Validate(applicant.Name, applicant.Age, applicant.Address))
                .Returns(true);

            var mockCreditScorer = new Mock<ICreditScorer>();

            var processor = new LoanApplicationProcessor(mockIdentityVerifier.Object, mockCreditScorer.Object);
            processor.Process(application);

            Assert.IsTrue(application.IsAccepted);
        }
    }
}

_creditScorer.CalculateScore(application.Applicant.Name, application.Applicant.Address);
if (_creditScorer.Score < MinimumCreditScore)
{
    return application.IsAccepted;
}

var mockIdentityVerifier = new Mock<IIdentityVerifier>();
mockIdentityVerifier.Setup(x => x.Validate(
        //applicant.Name,
        It.IsAny<string>(),
        applicant.Age, 
        applicant.Address))
    .Returns(true);

var mockIdentityVerifier = new Mock<IIdentityVerifier>();
mockIdentityVerifier.Setup(x => x.Validate(
        //applicant.Name,
        It.IsAny<string>(),
        //applicant.Age,
        It.IsAny<int>(),
        //applicant.Address
        It.IsAny<string>()
        ))
    .Returns(true);

using Loans.Models;

namespace Loans.Services.Contracts
{
    public interface IIdentityVerifier
    {
        void Validate(string applicantName, int applicantAge, string applicantAddress, out bool isValid);
// ...
    }
}

//var isValidIdentity = _identityVerifier.Validate(
//    application.Applicant.Name, application.Applicant.Age, application.Applicant.Address);
_identityVerifier.Validate(
    application.Applicant.Name, application.Applicant.Age, application.Applicant.Address,
    out var isValidIdentity);

var isValidOutValue = true;
mockIdentityVerifier.Setup(x => x.Validate(applicant.Name,
    applicant.Age,
    applicant.Address,
    out isValidOutValue));

using Loans.Models;

namespace Loans.Services.Contracts
{
    public interface IIdentityVerifier
    {        
          void Validate(string applicantName, int applicantAge, string applicantAddress,
                             ref IdentityVerificationStatus status);
// ...
    }
}

namespace Loans.Models
{
    public class IdentityVerificationStatus
    {
        public bool Passed { get; set; }
    }
}

IdentityVerificationStatus status = null;
  _identityVerifier.Validate(
      application.Applicant.Name, application.Applicant.Age, application.Applicant.Address,
      ref status);

if (!status.Passed)
{
    return application.IsAccepted;
}

delegate void ValidateCallback(string applicantName,
    int applicantAge,
    string applicantAddress,
    ref IdentityVerificationStatus status);

mockIdentityVerifier
    .Setup(x => x.Validate(applicant.Name,
        applicant.Age,
        applicant.Address,
        ref It.Ref<IdentityVerificationStatus>.IsAny))
    .Callback(new ValidateCallback(
        (string applicantName,
         int applicantAge,
         string applicantAddress,
         ref IdentityVerificationStatus status) =>
            status = new IdentityVerificationStatus {Passed = true}));

namespace Loans.Services.Contracts
{
    public interface INullExample
    {
        string SomeMethod();
    }
}

namespace Loans.Tests
{
    [TestClass]
    public class LoanApplicationProcessorShould
    {        
        [TestMethod]
        public void NullReturnExample()
        {
            var mock = new Mock<INullExample>();

            mock.Setup(x => x.SomeMethod());
            //.Returns<string>(null);

            string mockReturnValue = mock.Object.SomeMethod();

            Assert.IsNull(mockReturnValue);
        }
    }
}

Declare @MyDate JalaliDate = '1392/02/11 21:38:24'
Select @MyDate.ToString() as MyDateTime
           , @MyDate.GetDate() as MyDate
           , @MyDate.GetTime() as MyTime
           , @MyDate.Year as MyYear
           , @MyDate.Month as MyMonth
          , @MyDate.Day as MyDay
          , @MyDate.Hour as MyHour
          , @MyDate.Minute as MyMinute
          , @MyDate.Second as MySecond
          , @MyDate.JalaliDateAdd('Year',1) as NextYear
          , @MyDate.JalaliDateAdd('Month',1) as NextMonth
          , @MyDate.JalaliDateAdd('Day',1) as NextDay
          , @MyDate.JalaliDateAdd('Hour',1) as NextHour
          , @MyDate.JalaliDateAdd('Minute',1) as NextMinute
          , @MyDate.JalaliDateAdd('Second',1) as NextSecond

using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;

public partial class UserDefinedFunctions
{
    [Microsoft.SqlServer.Server.SqlFunction]
    public static JalaliDate GetCurrentDateTime()
    {
        System.Globalization.PersianCalendar pers = new System.Globalization.PersianCalendar();
        DateTime CurrentDate = DateTime.Now;
        JalaliDate jl;
        jl.Year = (Int16)pers.GetYear(CurrentDate);
        jl.Month = (byte)pers.GetMonth(CurrentDate);
        jl.Day = (byte)pers.GetDayOfMonth(CurrentDate);
        jl.Hour = (byte)pers.GetHour(CurrentDate);
        jl.Minute = (byte)pers.GetMinute(CurrentDate);
        jl.Second = (byte)pers.GetSecond(CurrentDate);
        return jl;
    }
}

Declare @MyDate JalaliDate = dbo.GetCurrentDateTime()

Select dbo.GetCurrentDateTime().ToString()

public class UserFactory
{
    public User CreateUser(string email) {
        return new User(email);
    }
}

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

namespace ValueOf
{
    public class ValueOf<TValue, TThis> where TThis : ValueOf<TValue, TThis>, new()
    {
        private static readonly Func<TThis> Factory;

        /// <summary>
        /// WARNING - THIS FEATURE IS EXPERIMENTAL. I may change it to do
        /// validation in a different way.
        /// Right now, override this method, and throw any exceptions you need to.
        /// Access this.Value to check the value
        /// </summary>
        protected virtual void Validate()
        {
        }

        static ValueOf()
        {
            ConstructorInfo ctor = typeof(TThis)
                .GetTypeInfo()
                .DeclaredConstructors
                .First();

            var argsExp = new Expression[0];
            NewExpression newExp = Expression.New(ctor, argsExp);
            LambdaExpression lambda = Expression.Lambda(typeof(Func<TThis>), newExp);

            Factory = (Func<TThis>)lambda.Compile();
        }

        public TValue Value { get; protected set; }

        public static TThis From(TValue item)
        {
            TThis x = Factory();
            x.Value = item;
            x.Validate();

            return x;
        }

        protected virtual bool Equals(ValueOf<TValue, TThis> other)
        {
            return EqualityComparer<TValue>.Default.Equals(Value, other.Value);
        }

        public override bool Equals(object obj)
        {
            if (obj is null)
                return false;

            if (ReferenceEquals(this, obj))
                return true;

            return obj.GetType() == GetType() && Equals((ValueOf<TValue, TThis>)obj);
        }

        public override int GetHashCode()
        {
            return EqualityComparer<TValue>.Default.GetHashCode(Value);
        }

        public static bool operator ==(ValueOf<TValue, TThis> a, ValueOf<TValue, TThis> b)
        {
            if (a is null && b is null)
                return true;

            if (a is null || b is null)
                return false;

            return a.Equals(b);
        }

        public static bool operator !=(ValueOf<TValue, TThis> a, ValueOf<TValue, TThis> b)
        {
            return !(a == b);
        }

        public override string ToString()
        {
            return Value.ToString();
        }
    }
}

public class EmailAddress : ValueOf<string, EmailAddress> { }

EmailAddress emailAddress = EmailAddress.From("foo@bar.com");

public class Address : ValueOf<(string firstLine, string secondLine, Postcode postcode), Address> { }