namespace Loans.Entities
{
    public class Applicant
    {
        public int Id { set; get; }

        public string Name { set; get; }

        public int Age { set; get; }

        public string Address { set; get; }

        public decimal Salary { set; get; }
    }
}

namespace Loans.Entities
{
    public class LoanProduct
    {
        public int Id { set; get; }

        public string ProductName { set; get; }

        public decimal InterestRate { set; get; }
    }
}

namespace Loans.Entities
{
    public class LoanApplication
    {
        public int Id { set; get; }

        public LoanProduct Product { set; get; }

        public LoanAmount Amount { set; get; }

        public Applicant Applicant { set; get; }

        public bool IsAccepted { set; get; }
    }

    public class LoanAmount
    {
        public string CurrencyCode { get; set; }

        public decimal Principal { get; set; }
    }
}

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

using Loans.Models;

namespace Loans.Services.Contracts
{
    public interface IIdentityVerifier
    {
        void Initialize();

        bool Validate(string applicantName, int applicantAge, string applicantAddress);

        void Validate(string applicantName, int applicantAge, string applicantAddress, out bool isValid);

        void Validate(string applicantName, int applicantAge, string applicantAddress,
            ref IdentityVerificationStatus status);
    }
}

namespace Loans.Services.Contracts
{
    public interface ICreditScorer
    {
        int Score { get; }

        void CalculateScore(string applicantName, string applicantAddress);
    }
}

using System;
using Loans.Entities;
using Loans.Services.Contracts;

namespace Loans.Services
{
    public class LoanApplicationProcessor
    {
        private const decimal MinimumSalary = 1_500_000_0;
        private const int MinimumAge = 18;
        private const int MinimumCreditScore = 100_000;

        private readonly IIdentityVerifier _identityVerifier;
        private readonly ICreditScorer _creditScorer;

        public LoanApplicationProcessor(
            IIdentityVerifier identityVerifier,
            ICreditScorer creditScorer)
        {
            _identityVerifier = identityVerifier ?? throw new ArgumentNullException(nameof(identityVerifier));
            _creditScorer = creditScorer ?? throw new ArgumentNullException(nameof(creditScorer));
        }

        public bool Process(LoanApplication application)
        {
            application.IsAccepted = false;

            if (application.Applicant.Salary < MinimumSalary)
            {
                return application.IsAccepted;
            }

            if (application.Applicant.Age < MinimumAge)
            {
                return application.IsAccepted;
            }

            _identityVerifier.Initialize();

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

            if (!isValidIdentity)
            {
                return application.IsAccepted;
            }

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

            application.IsAccepted = true;
            return application.IsAccepted;
        }
    }
}

using System;
using Loans.Models;
using Loans.Services.Contracts;

namespace Loans.Services
{
    public class IdentityVerifierServiceGateway : IIdentityVerifier
    {
        public DateTime LastCheckTime { get; private set; }

        public void Initialize()
        {
            // Initialize connection to external service
        }

        public bool Validate(string applicantName, int applicantAge, string applicantAddress)
        {
            Connect();
            var isValidIdentity = CallService(applicantName, applicantAge, applicantAddress);
            LastCheckTime = DateTime.Now;
            Disconnect();

            return isValidIdentity;
        }

        private void Connect()
        {
            // Open connection to external service
        }

        private bool CallService(string applicantName, int applicantAge, string applicantAddress)
        {
            // Make call to external service, interpret the response, and return result

            return false; // Simulate result for demo purposes
        }

        private void Disconnect()
        {
            // Close connection to external service
        }

        public void Validate(string applicantName, int applicantAge, string applicantAddress, out bool isValid)
        {
            throw new NotImplementedException();
        }

        public void Validate(string applicantName, int applicantAge, string applicantAddress,
            ref IdentityVerificationStatus status)
        {
            throw new NotImplementedException();
        }
    }
}

        public LoanApplicationProcessor(
            IIdentityVerifier identityVerifier,
            ICreditScorer creditScorer)
        {
            _identityVerifier = identityVerifier ?? throw new ArgumentNullException(nameof(identityVerifier));
            _creditScorer = creditScorer ?? throw new ArgumentNullException(nameof(creditScorer));
        }

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp2.2</TargetFramework>
  </PropertyGroup>
  <ItemGroup>
    <ProjectReference Include="..\Loans\Loans.csproj" />
  </ItemGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.3.0" />
    <PackageReference Include="MSTest.TestAdapter" Version="2.0.0" />
    <PackageReference Include="MSTest.TestFramework" Version="2.0.0" />    
  </ItemGroup>
</Project>

using Loans.Entities;
using Loans.Services;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace Loans.Tests
{
    [TestClass]
    public class LoanApplicationProcessorShould
    {
        [TestMethod]
        public void DeclineLowSalary()
        {
            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_100_000_0};
            var application = new LoanApplication {Id = 42, Product = product, Amount = amount, Applicant = applicant};
            var processor = new LoanApplicationProcessor(null, null);
            processor.Process(application);

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

public class LoanApplicationProcessor
{
    private const decimal MinimumSalary = 1_500_000_0;

Test method Loans.Tests.LoanApplicationProcessorShould.DeclineLowSalary threw exception:
System.ArgumentNullException: Value cannot be null.
Parameter name: identityVerifier

        public LoanApplicationProcessor(
            IIdentityVerifier identityVerifier,
            ICreditScorer creditScorer)
        {
            _identityVerifier = identityVerifier ?? throw new ArgumentNullException(nameof(identityVerifier));
            _creditScorer = creditScorer ?? throw new ArgumentNullException(nameof(creditScorer));
        }

> dotnet add package Moq
> Install-Package Moq

using Loans.Entities;
using Loans.Services;
using Loans.Services.Contracts;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;

namespace Loans.Tests
{
    [TestClass]
    public class LoanApplicationProcessorShould
    {
        [TestMethod]
        public void DeclineLowSalary()
        {
            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_100_000_0};
            var application = new LoanApplication {Id = 42, Product = product, Amount = amount, Applicant = applicant};

            var mockIdentityVerifier = new Mock<IIdentityVerifier>();
            var mockCreditScorer = new Mock<ICreditScorer>();

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

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

using Loans.Entities;
using Loans.Services;
using Loans.Services.Contracts;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using Moq;

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>();
            var mockCreditScorer = new Mock<ICreditScorer>();

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

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

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

 public string FirstName { get; set; }

       private string firstName;

       public string FirstName
        {
            get { return firstName; }
            set { firstName = value; }
        }

http://hostname/api/products/28

namespace ProductStore.Models
{
    public class Product
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Category { get; set; }
        public decimal Price { get; set; }
    }
}

namespace ProductStore.Models
{
    public interface IProductRepository
    {
        IEnumerable<Product> GetAll();
        Product Get(int id);
        Product Add(Product item);
        void Remove(int id);
        bool Update(Product item);
    }
}

namespace ProductStore.Models
{
    public class ProductRepository : IProductRepository
    {
        private List<Product> products = new List<Product>();
        private int _nextId = 1;

        public ProductRepository()
        {
            Add(new Product { Name = "Tomato soup", Category = "Groceries", Price = 1.39M });
            Add(new Product { Name = "Yo-yo", Category = "Toys", Price = 3.75M });
            Add(new Product { Name = "Hammer", Category = "Hardware", Price = 16.99M });
        }

        public IEnumerable<Product> GetAll()
        {
            return products;
        }

        public Product Get(int id)
        {
            return products.Find(p => p.Id == id);
        }

        public Product Add(Product item)
        {
            if (item == null)
            {
                throw new ArgumentNullException("item");
            }
            item.Id = _nextId++;
            products.Add(item);
            return item;
        }

        public void Remove(int id)
        {
            products.RemoveAll(p => p.Id == id);
        }

        public bool Update(Product item)
        {
            if (item == null)
            {
                throw new ArgumentNullException("item");
            }
            int index = products.FindIndex(p => p.Id == item.Id);
            if (index == -1)
            {
                return false;
            }
            products.RemoveAt(index);
            products.Add(item);
            return true;
        }
    }
}

using ProductStore.Models;

public class ProductsController : ApiController
{
    static readonly IProductRepository repository = new ProductRepository();
}

public class ProductsController : ApiController
{
    public IEnumerable<Product> GetAllProducts()
    {
        return repository.GetAll();
    }
    // ....
}

public Product GetProduct(int id)
{
    Product item = repository.Get(id);
    if (item == null)
    {
        throw new HttpResponseException(HttpStatusCode.NotFound); 
    }
    return item;
}

public IEnumerable<Product> GetProductsByCategory(string category)
{
    return repository.GetAll().Where(
        p => string.Equals(p.Category, category, StringComparison.OrdinalIgnoreCase));
}

// Not the final implementation!
public Product PostProduct(Product item)
{
    item = repository.Add(item);
    return item;
}

public HttpResponseMessage PostProduct(Product item)
{
    item = repository.Add(item);
    var response = Request.CreateResponse<Product>(HttpStatusCode.Created, item);

    string uri = Url.Link("DefaultApi", new { id = item.Id });
    response.Headers.Location = new Uri(uri);
    return response;
}

public void PutProduct(int id, Product product)
{
    product.Id = id;
    if (!repository.Update(product))
    {
        throw new HttpResponseException(HttpStatusCode.NotFound);
    }
}

public void DeleteProduct(int id)
{
    Product item = repository.Get(id);
    if (item == null)
    {
        throw new HttpResponseException(HttpStatusCode.NotFound);
    }

    repository.Remove(id);
}

تا به اینجا توانستیم فقط با نوشتن آدرس API مورد نظر، آن را فراخوانی کنیم.

برای ارسال پارامترهایی در هدر درخواست فقط کافیست دقیقا در خط پایین آدرس، به صورت field-name:field-value، هر پارامتری را که میخواهید، به همراه درخواست ارسال کنید. برای نمونه برای API لیست افراد که در بالا تست کردیم، میتوانیم هدر را به صورت زیر تنظیم نماییم :

GET http://localhost:59416/api/people
Content-Type: application/json

اجرای درخواست GET برای دریافت یک شخص خاص

GET http://localhost:59416/api/people/1

خروجی آن به صورت زیر می‌باشد

درخواست POST برای درج کاربر جدید:

POST http://localhost:59416/api/people
content-type: application/json

{
    "id": 10,
    "name": "ali",
    "age":37
}

بعد از هدرهای درخواست، یک خط خالی ایجاد کنید و پایین‌تر از خط خالی، میتوانید مقادیر body درخواست را وارد نمایید.

درخواست PUT برای آپدیت یک شخص :

PUT http://localhost:59416/api/people/3
content-type: application/json

{
    "id": 3,
    "name": "ali",
    "age":37
}

درخواست DELETE برای حذف شخص:

DELETE http://localhost:59416/api/people/3
content-type: application/application/json

ارسال توکن اعتبارسنجی :

در صورتی که یک API نیاز به اعتبار سنجی دارد و باید توکن را به همراه درخواستی ارسال نمایید، می‌توانید در هدر درخواست، همانند زیر، توکن را ارسال نمایید

GET http://localhost:59416/api/people
content-type: application/json
Authorization: Bearer token

آپلود فایل:

یکی از API هایی که در مثال ابتدای مقاله داشتیم، مربوط به آپلود فایل آواتار هست که از ورودی، یک IFormFile را به عنوان ورودی دریافت میکند. برای آپلود فایل به کمک افزونه Rest Client میتوانیم به صورت زیر فایل را ارسال نماییم 

POST http://localhost:59416/api/people/avatar
Content-Type: multipart/form-data; boundary=----MyBoundary

------MyBoundary
Content-Disposition: form-data; name="file";filename="Studio"
content-type: image/png

< C:\Users\rahimi\Downloads\Studio.png

------MyBoundary--

قبل از آدرس فایل، وجود  > ضروری می‌باشد. 

فعال سازی دکمه Send Request به ازای هر آدرس:

اگر در یک فایل، چند آدرس را همانند عکس زیر داشته باشید، فقط یک دکمه‌ی Send Request وجود خواهد داشت که کلیک بر روی آن منجر به فراخوانی اولین url می‌شود.

برای داشتن یک دکمه Send Request به ازای هر API، باید بین هر کدام از API ها، حداقل سه تا # قرار دهید.

### Get All People
GET http://localhost:59416/api/people
content-type: application/json

### Get Person
GET http://localhost:59416/api/people/1


### Create 
POST http://localhost:59416/api/people
content-type: application/json

{
    "id": 10,
    "name": "ali",
    "age":37
}

### Edit person
PUT http://localhost:59416/api/people/3
content-type: application/json

{
    "id": 3,
    "name": "ali",
    "age":37
}

### Delete person
DELETE http://localhost:59416/api/people/3
content-type: application/application/json


### Upload Avatar
POST http://localhost:59416/api/people/avatar 
Content-Type: multipart/form-data; boundary=----MyBoundary

------MyBoundary
Content-Disposition: form-data; name="file";filename="Studio"
content-type: image/png

< C:\Users\rahimi\Downloads\Studio.png

------MyBoundary--

افزونه‌ی Rest Client، فراتر از توضیحات این مقاله می‌باشد. در صورت علاقه و برای مطالعه بیشتر در مورد آن، می‌توانید به لینک صفحه افزونه مراجعه نمایید.

public class Book:Entity
    {
        public string Title { get; set; }
        public string ISBN { get; set; }
        public int Price { get; set; }
        public List<Author> Authors { get; set; }
        public BsonDocument ExtraFields { get; set; }
        public Language Language { get; set; }
        public ObjectId Image { get; set; }
        public int Year { get; set; }
        public DateTime LastStock { get; set; }

    }

     var book = new Book()
            {
      
                Title = "Gone With Wind",
                ISBN = "43442424",
                Price = 50000,
                Year = 1936,
                LastStock = DateTime.Now.AddDays(-13),
                Language = new Language()
                {
                    Name = "Persian"
                },
                Authors = new List<Author>()
               {
                   new Author()
                   {
                       Name = "Margaret Mitchell"
                   }
               },
                ExtraFields=new BsonDocument("Translator", "Ali Mahboobi")
            };

همینطور که می‌بینید این فیلد جدید به عنوان یک شیء جدا یا یک سند توکار ذخیره شده‌است. ولی اگر میخواهید به عنوان یک فیلد، همانند دیگر فیلدها ذخیره شود، باید فیلد ExtraField را به ویژگی BsonExtraElement مزین کنید. پس مدل را به شکل زیر بازنویسی میکنیم:

public class Book:Entity
    {
        public string Title { get; set; }
        public string ISBN { get; set; }
        public int Price { get; set; }
        public List<Author> Authors { get; set; }
        [BsonExtraElements]
        public BsonDocument ExtraFields { get; set; }
        public Language Language { get; set; }
        public ObjectId Image { get; set; }
        public int Year { get; set; }
        public DateTime LastStock { get; set; }

    }

public class ApplicationDbContext : IdentityDbContext<ApplicationUser>
{
    public ApplicationDbContext() : base("DefaultConnection") { }
}

public class AppUserManager : UserManager<AppUser>{
    public AppUserManager() : base(new UserStore<AppUser>(new ShirazBilitDbContext())) { }
}

public class AppUser : IdentityUser
{
    public string Email { get; set; }
    public string ConfirmationToken { get; set; }
    public bool IsConfirmed { get; set; }
}

public class Rectangle
{
    public int Length { get; set; }
    public int Height { get; set; }

    public void Grow(int length, int height)
    {
        Length += length;
        Height += height;
    }
}

Rectangle r = new Rectangle();
r.Length = 5;
r.Height = 10;
r.Grow(10, 10);// r.Length is 15, r.Height is 20, same instance of r

// After
public class ImmutableRectangle
{
    int Length { get; }
    int Height { get; }

    public ImmutableRectangle(int length, int height)
    {
        Length = length;
        Height = height;
    }

    public ImmutableRectangle Grow(int length, int height) =>
          new ImmutableRectangle(Length + length, Height + height);
}

ImmutableRectangle r = new ImmutableRectangle(5, 10);
r = r.Grow(10, 10);// r.Length is 15, r.Height is 20, is a new instance of r

public static void Main()
{
    Console.WriteLine(GetSalutation(DateTime.Now.Hour));
}

// imparitive, mutates state to produce a result
/*public static string GetSalutation(int hour)
{
    string salutation; // placeholder value

    if (hour < 12)
        salutation = "Good Morning";
    else
        salutation = "Good Afternoon";

    return salutation; // return mutated variable
}*/

public static string GetSalutation(int hour) => hour < 12 ? "Good Morning" : "Good Afternoon";

public static int Count<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate)
{
    int count = 0;

    foreach (TSource element in source)
    {
        checked
        {
            if (predicate(element))
            {
                count++;
            }
        }
    }

    return count;
}

public static class Extensions
{
    public static Func<T, TReturn2> Compose<T, TReturn1, TReturn2>(this Func<TReturn1, TReturn2> func1, Func<T, TReturn1> func2)
    {
        return x => func1(func2(x));
    }
}

public class Program
{
    public static void Main(string[] args)
    {
        Func<int, int> square = (x) => x * x;
        Func<int, int> negate = x => x * -1;
        Func<int, string> toString = s => s.ToString();
        Func<int, string> squareNegateThenToString = toString.Compose(negate).Compose(square);
        Console.WriteLine(squareNegateThenToString(2));
    }
}

string str = new StringBuilder()
  .Append("Hello ")
  .Append("World ")
  .ToString()
  .TrimEnd()
  .ToUpper();

public static class Extensions
{
    public static StringBuilder AppendWhen(this StringBuilder sb, string value, bool predicate) => predicate ? sb.Append(value) : sb;
}

public class Program
{
    public static void Main(string[] args)
    {
        // Extends the StringBuilder class to accept a predicate
        string htmlButton = new StringBuilder().Append("<button").AppendWhen(" disabled", false).Append(">Click me</button>").ToString();
    }
}

public static void Main()
{
    int[] a = { 1, 2, 3, 4, 5 };

    foreach (int n in GreaterThan(a, 3))
    {
        Console.WriteLine(n);
    }
}


/*public static IEnumerable<int> GreaterThan(int[] arr, int gt)
{
    List<int> temp = new List<int>();
    foreach (int n in arr)
    {
        if (n > gt) temp.Add(n);
    }
    return temp;
}*/

public static IEnumerable<int> GreaterThan(int[] arr, int gt)
{
    foreach (int n in arr)
    {
        if (n > gt) yield return n;
    }
}

List<int> collection = new List<int> { 1, 2, 3, 4, 5 };

// Imparative style of programming is verbose
List<int> results = new List<int>();

foreach(var num in collection)
{
  if (num % 2 != 0) results.Add(num);
}

// Declarative is terse and beautiful
var results = collection.Where(num => num % 2 != 0);