Getting Started with ASP.NET Web API 2 (C#) Part 1

- ASP.NET Web API is a framework for building HTTP services(web APIs on top of the .NET Framework. ) that can be consumed by a broad range of clients including browsers, mobiles, iphone and tablets. 
- ASP.NET Web API has been around for some years now. It is a very efficient and lightweight technology to build RESTful web services in .NET.
- Web API is very similar to ASP.NET MVC since it contains the MVC features such as routing, controllers, action results, filter, model binders, IOC container or dependency injection. 
-  Therefore if you are familiar with MVC then it’s easy to understand Web API either.

DEMO
In this tutorial, you will use ASP.NET Web API to create a web API that returns a list of products. 
I’m building the demo using Visual Studio 2013 Professional.
So open VS 2013 and create a new ASP.NET web project called ProductDataClient

Click OK and then select the Web API template:

Check The Authentication. It should be Individual User Accounts. If not then click Change Authentication and make it  Individual User Accounts from the list of options.

Click OK

Now you’ll have a project structure like this

Press F5 or Run the project. you’ll see a default web site.

It look like a normal MVC website. But some differences are there like
- no link to log in or sign up new users anywhere. 

So what's new .. There is API link, up in the navigation bar. 
Click on that ,This is a documentation page for the available URL endpoints of the web api.

Click on GET api/values and you’ll see an example for the JSON and XML response structures:

If you check out one of the POST urls then the documentation will show you the expected request body format as well:
Click on POST api/Account/Register

The documentation is provided by a pre-installed NuGet package: Microsoft.AspNet.WebApi.HelpPage. It will look for ApiControllers in your project and any documentation available on them using Reflection. You won’t find an assembly reference to this package under the References section so don’t look for it. However, there’s a HelpPage area in the solution:

The controllers, models and views in this area help construct the Documentation page we’ve just seen. Any new API controller you create will be added to the documentation. You can add comments in the usual way: just decorate the Controller with VS XML comments:
Go to ValuesController and add comments like this

Also, you need to let VS generate an XML documentation file:
Right click on the project and select Properties

Click on Build

We’re not done yet. Locate the HelpPageConfig.cs file in the Areas/HelpPage/App_Start folder. There will be some code already but it’s all commented out. Uncomment the first line and modify the file name to match what you provided in the previous step:

Rebuild and run the project. If you get a runtime exception saying that the documentation XML file wasn’t found then check the file URL again in the code we’ve just commented out. It may have been overwritten. The documentation page should show the new description:

Values controller

You can call the values controller in the browser to check if the Get() method is working. The URL should be http://localhost:59693/api/values. The port number in your case may of course differ. At first you should get an error message saying that the request was unauthorised. That’s because the ValuesController has been decorated with the [Authorize] attribute. 

Uncomment it and refresh the page. You should see an XML with the default values returned.

Model data

Any demo on the Web API is futile without a data source. Let’s build a class hierarchy in the Models folder. Note that your domains should exist in a separate project of course but this post is not about layered architecture but the Web API. 

In this we are working with in-memory data.

Locate the Models folder and add a new folder in it called Domain. We’ll build a simple data hierarchy . Add the following classes to the Domain folder:

Next we’ll set up the in-memory repository to get some data to start with.

Insert a new folder called Repository in Model Folder and Create InMemoryDataContext.cs .

namespace ProductDataClient.Models.Repository
{
    public class InMemoryDataContext
   {
        private List<ProductList> _productList;

        public InMemoryDataContext()
        {
            _productList = ProductLists();
        }

        public IEnumerable<ProductList> GetAll()
        {
            return _productList;
        }

        public static InMemoryDataContext Instance
        {
         get
         {
           return Nested.instance;
         }
        }

        private class Nested
        {
         static Nested()
         {
         }
         internal static readonly InMemoryDataContext instance = new InMemoryDataContext();
        }

        private List<ProductList> ProductLists()
        {
            List<ProductList> productList = new List<ProductList>();

            ProductList p1 = new ProductList();
            p1.Name = "Great band";
            p1.Id = 1;
            p1.Albums = new List<Album>(){new Album(){Title = "First album", Year = 2000}, new Album(){Title = "Second album", Year = 2003}
                , new Album(){Title = "Third album", Year=2005}};
            p1.Prizes = new List<Prize>() { new Prize() { Name = "Best band" }, new Prize() { Name = "Best newcomers" } };

            ProductList p2 = new ProductList();
            p2.Name = "Funny band";
            p2.Id = 2;
            p2.Albums = new List<Album>(){new Album(){Title = "Debut", Year = 1979}, new Album(){Title = "Continuation", Year = 1980}
                , new Album(){Title = "New Year", Year=1982}, new Album(){Title ="Summer", Year=1985}};
            p2.Prizes = new List<Prize>() { new Prize() { Name = "Cool band" }, new Prize() { Name = "Best band" }, new Prize() { Name = "First choice" } };

            ProductList p3 = new ProductList();
            p3.Name = "Sounds good";
            p3.Id = 3;
            p3.Albums = new List<Album>() { new Album() { Title = "The beginning", Year = 1982 }, new Album() { Title = "The end", Year = 1986 } };
            p3.Prizes = new List<Prize>() { new Prize() { Name = "First choice" } };

            ProductList rb = new ProductList();
            rb.Name = "Sounds good";
            rb.Id = 4;
            rb.Albums = new List<Album>() { new Album() { Title = "Cool", Year = 1988 }, new Album() { Title = "Yeah", Year = 1989 }
                , new Album() { Title = "Oooooohhh", Year = 1990 }, new Album() { Title = "Entertain", Year = 1991 }, new Album() { Title = "Go home", Year = 1992 }};
            rb.Prizes = new List<Prize>() { new Prize() { Name = "First choice" }, new Prize() { Name = "Cool band" } };

            productList.Add(p1);
            productList.Add(p2);
            productList.Add(p3);
            productList.Add(rb);

            return productList;
        }
}

}

Add the following components necessary for the thread safe lazy singleton pattern:

Add one interface file in Model Folder

We have our data store so we’d like to extract the Productlist data via an API call.

Product controller

Right click the Controllers folder and select Add and then Controller from the context menu. The Add Scaffold window will appear. Select the Web API 2 Controller – Empty option and click Add. In the Add Controller window insert the controller name: ProductController. The new controller will derive from ApiController as expected.

Add the following private field and constructor to the controller:

Insert the following Get() method into the controller:

public IEnumerable<ProductList> Get()
        {
            return _objectContextFactory.Create().GetAll();

        }

RUN => redirect 
http://localhost:59693/api/Product 

Add caption

DONE :)