first commit

After/Customer.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.After
+{
+    internal class Customer
+    {
+        public int Id { get; set; }
+        public string Name { get; set; }
+        public string EmailAddress { get; set; }
+        public string MobileNo { get; set; }
+        public string Address { get; set; }
+    }
+}

After/EmailService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.After
+{
+    internal class EmailService: IMessageService
+    {
+        public string EmailAddress { get; set; }
+
+        public void Send()
+        {
+            Console.WriteLine($"E-mail is sent to {EmailAddress}");
+        }
+    }
+}

After/IMessageService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.After
+{
+    internal interface IMessageService
+    {
+        void Send();
+    }
+}

After/NotificationService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.After
+{
+    class NotificationService
+    {
+        public readonly List<IMessageService> _services;
+
+        public NotificationService(List<IMessageService> services)
+        {
+            _services = services;
+        }
+
+        public void Notify()
+        {
+            foreach (var service in _services)
+            {
+                service.Send();
+            }
+        }
+    }
+}

After/Repository.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.After
+{
+    internal static class Repository
+    {
+        public static List<Customer> Customers =>
+            new List<Customer>()
+            {
+                new Customer
+                {
+                    Id = 1,
+                    Name = "John Doe",
+                    EmailAddress = "[email protected]",
+                    MobileNo = "+1 (606) 123-4567",
+                    Address = "123 2nd Avenue California, USA"
+                },
+                new Customer
+                {
+                    Id = 2,
+                    Name = "Sarah MC",
+                    EmailAddress = "[email protected]",
+                    MobileNo = "+1 (606) 124-4567",
+                    Address = "345 4th Avenue Florida, USA"
+                },
+                new Customer
+                {
+                    Id = 3,
+                    Name = "Steve Pado",
+                    EmailAddress = "[email protected]",
+                    MobileNo = "+1 (606) 123-4567",
+                    Address = "678 3rd Avenue Chicago, USA"
+                }
+            };
+
+    }
+}

After/SMSService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.After
+{
+    internal class SMSService: IMessageService
+    {
+        public string MobileNo { get; set; }
+
+        public void Send()
+        {
+            Console.WriteLine($"SMS is sent to {MobileNo}");
+        }
+    }
+}

App.config

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+<?xml version="1.0" encoding="utf-8" ?>
+<configuration>
+    <startup> 
+        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.8" />
+    </startup>
+</configuration>

Before/Customer.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.Before
+{
+    internal class Customer
+    {
+        public int Id { get; set; }
+        public string Name { get; set; }
+        public string EmailAddress { get; set; }
+        public string MobileNo { get; set; }
+        public string Address { get; set; }
+    }
+}

Before/EmailService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.Before
+{
+    internal class EmailService
+    {
+        public string EmailAddress { get; set; }
+
+        public void Send()
+        {
+            Console.WriteLine($"E-mail is sent to {EmailAddress}");
+        }
+    }
+}

Before/NotificationService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.Before
+{
+    class NotificationService
+    {
+        private readonly Customer customer;
+        private readonly EmailService emailService;
+        private readonly SMSService smsService;
+
+        public NotificationService(Customer customer)
+        {
+            emailService = new EmailService
+            {
+                EmailAddress = customer.EmailAddress
+            };
+
+            smsService = new SMSService
+            {
+                MobileNo = customer.MobileNo
+            };
+        }
+
+        public void Notify()
+        {
+            emailService.Send();
+            smsService.Send();
+        }
+    }
+}

Before/Repository.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.Before
+{
+    internal static class Repository
+    {
+        public static List<Customer> Customers =>
+            new List<Customer>()
+            {
+                new Customer
+                {
+                    Id = 1,
+                    Name = "John Doe",
+                    EmailAddress = "[email protected]",
+                    MobileNo = "+1 (606) 123-4567",
+                    Address = "123 2nd Avenue California, USA"
+                },
+                new Customer
+                {
+                    Id = 2,
+                    Name = "Sarah MC",
+                    EmailAddress = "[email protected]",
+                    MobileNo = "+1 (606) 124-4567",
+                    Address = "345 4th Avenue Florida, USA"
+                },
+                new Customer
+                {
+                    Id = 3,
+                    Name = "Steve Pado",
+                    EmailAddress = "[email protected]",
+                    MobileNo = "+1 (606) 123-4567",
+                    Address = "678 3rd Avenue Chicago, USA"
+                }
+            };
+
+    }
+}

Before/SMSService.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion.Before
+{
+    internal class SMSService
+    {
+        public string MobileNo { get; set; }
+
+        public void Send()
+        {
+            Console.WriteLine($"SMS is sent to {MobileNo}");
+        }
+    }
+}

DependencyInversion.csproj

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+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" Condition="Exists('$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props')" />
+  <PropertyGroup>
+    <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
+    <Platform Condition=" '$(Platform)' == '' ">AnyCPU</Platform>
+    <ProjectGuid>{CFEE2B3E-E75C-4E4F-8922-18E3E38CDA0E}</ProjectGuid>
+    <OutputType>Exe</OutputType>
+    <RootNamespace>DependencyInversion</RootNamespace>
+    <AssemblyName>DependencyInversion</AssemblyName>
+    <TargetFrameworkVersion>v4.8</TargetFrameworkVersion>
+    <FileAlignment>512</FileAlignment>
+    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
+    <Deterministic>true</Deterministic>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <DebugSymbols>true</DebugSymbols>
+    <DebugType>full</DebugType>
+    <Optimize>false</Optimize>
+    <OutputPath>bin\Debug\</OutputPath>
+    <DefineConstants>DEBUG;TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
+    <PlatformTarget>AnyCPU</PlatformTarget>
+    <DebugType>pdbonly</DebugType>
+    <Optimize>true</Optimize>
+    <OutputPath>bin\Release\</OutputPath>
+    <DefineConstants>TRACE</DefineConstants>
+    <ErrorReport>prompt</ErrorReport>
+    <WarningLevel>4</WarningLevel>
+  </PropertyGroup>
+  <ItemGroup>
+    <Reference Include="System" />
+    <Reference Include="System.Core" />
+    <Reference Include="System.Xml.Linq" />
+    <Reference Include="System.Data.DataSetExtensions" />
+    <Reference Include="Microsoft.CSharp" />
+    <Reference Include="System.Data" />
+    <Reference Include="System.Net.Http" />
+    <Reference Include="System.Xml" />
+  </ItemGroup>
+  <ItemGroup>
+    <Compile Include="After\Customer.cs" />
+    <Compile Include="After\EmailService.cs" />
+    <Compile Include="After\IMessageService.cs" />
+    <Compile Include="After\NotificationService.cs" />
+    <Compile Include="After\Repository.cs" />
+    <Compile Include="After\SMSService.cs" />
+    <Compile Include="Before\Customer.cs" />
+    <Compile Include="Before\EmailService.cs" />
+    <Compile Include="Before\NotificationService.cs" />
+    <Compile Include="Before\Repository.cs" />
+    <Compile Include="Before\SMSService.cs" />
+    <Compile Include="Program.cs" />
+    <Compile Include="Properties\AssemblyInfo.cs" />
+  </ItemGroup>
+  <ItemGroup>
+    <None Include="App.config" />
+  </ItemGroup>
+  <ItemGroup />
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>

Program.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace DependencyInversion
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            //var customers = Before.Repository.Customers;
+            //foreach (var customer in customers)
+            //{
+            //    var notificationService = new Before.NotificationService(customer);
+            //    notificationService.Notify();
+            //}
+
+            var customers = After.Repository.Customers;
+            foreach (var customer in customers)
+            {
+                var messageService = new List<After.IMessageService>
+                {
+                    new After.SMSService { MobileNo = customer.MobileNo},
+                    new After.EmailService { EmailAddress = customer.EmailAddress}
+                };
+
+                var notificationService = new After.NotificationService(messageService);
+                notificationService.Notify();
+
+            }
+
+            Console.ReadKey();
+        }
+    }
+}