Implement IServiceProviderFactory for easy integration and update README (#5)

* Implement IServiceProviderFactory and added AddUnity() extension

* Update README.md

Author: DaniilSokolyuk

README.md

@@ -4,4 +4,47 @@
 [![NuGet](https://img.shields.io/nuget/v/Unity.Microsoft.DependencyInjection.svg)](https://www.nuget.org/packages/Unity.Microsoft.DependencyInjection)
 
 # Unity.Microsoft.DependencyInjection
-Unity extension to integrate with Microsoft.Extensions.DependencyInjection compliant systems
+Unity extension to integrate with [Microsoft.Extensions.DependencyInjection.Abstractions](https://github.com/aspnet/DependencyInjection)  compliant systems
+
+## Get Started
+- Reference the `Unity.Microsoft.DependencyInjection` package from NuGet.
+```
+Install-Package Unity.Microsoft.DependencyInjection
+```
+
+## First way:
+- In the `WebHostBuilder` add `ConfigureServices(services => services.AddUnity())` method
+
+```C#
+public static IWebHost BuildWebHost(string[] args) =>
+    WebHost.CreateDefaultBuilder(args)
+        .ConfigureServices(services => services.AddUnity())
+        .UseStartup<Startup>()
+        .Build();
+```
+- Add method to your `Startup` class
+```C#
+public void ConfigureContainer(IUnityContainer container)
+{
+  container.RegisterType<IMyService, MyService>();
+}
+```
+
+## Second way:
+- In the `ConfigureServices` method of your `Startup` class...
+  - Register services from the `IServiceCollection`.
+  - Build your container.
+  - Call `ConfigureServices` extension on `IUnityContainer` and return it.
+
+```C#
+public IServiceProvider ConfigureServices(IServiceCollection services)
+{
+  services.AddMvc();
+  
+  var container = new UnityContainer();
+  
+  container.RegisterType<IMyService, MyService>();
+  
+  return container.ConfigureServices(services);
+}
+```

src/ServiceCollectionExtensions.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Unity.Microsoft.DependencyInjection
+{
+    public static class ServiceCollectionExtensions
+    {
+        public static IServiceCollection AddUnity(this IServiceCollection services, Action<IUnityContainer> configurationAction = null)
+        {
+            return services.AddSingleton<IServiceProviderFactory<IUnityContainer>>(new ServiceProviderFactory(configurationAction));
+        }
+    }
+}

src/ServiceProviderFactory.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace Unity.Microsoft.DependencyInjection
+{
+    internal class ServiceProviderFactory : IServiceProviderFactory<IUnityContainer>
+    {
+        private readonly Action<IUnityContainer> _configurationAction;
+
+        public ServiceProviderFactory(Action<IUnityContainer> configurationAction = null)
+        {
+            _configurationAction = configurationAction ?? (container => { });
+        }
+
+        public IUnityContainer CreateBuilder(IServiceCollection serviceCollection)
+        {
+            var unityContainer = new UnityContainer();
+
+            unityContainer.Configure(serviceCollection);
+
+            _configurationAction(unityContainer);
+
+            return unityContainer;
+        }
+
+        public IServiceProvider CreateServiceProvider(IUnityContainer unityContainer)
+        {
+            return new ServiceProvider(unityContainer);
+        }
+    }
+}