ASP.NET Web API is a framework that makes it easy to build HTTP services that reach a broad range of clients, including browsers and mobile devices. ASP.NET Web API is an ideal platform for building RESTful applications on the .NET Framework. Video : https://youtu.be/qwLBeg1CPSo Courtesy: http://www.ifourtechnolab.com

1. iFour ConsultancyASP.NET MVC Web API

2.  ASP.NET Web API
 Why ASP.NET MVC Web API?
 ASP.NET Web API Features
 ASP.NET Web API Design
 ASP.NET MVC Web API
 Routing Table
 Error & Exception Handling
 Model Validation
INDEX
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3.  Framework for building and consuming HTTP services that can reach a broad range of
clients including browsers, phones and tablets
 Use XML or JSON or something else with API. JSON is nice for mobile apps with slow
connections
 For example: Call an API from jQuery and better utilize the client's machine and browser
What is ASP.NET Web API?
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4.  It is built for all the other, non-human interactions website or service needs to support.
Think about jQuery code that's making an Ajax request, or a service interface that supports
a mobile client
 In these cases, the requests are coming from code and expect some kind of structured
data and specific HTTP Status Codes
These two are very complimentary, but different enough that trying to build out HTTP
services using ASP.NET MVC took a lot of work to get right
Why ASP.NET MVC Web API?
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5.  Modern HTTP programming model
 Directly access and manipulate HTTP requests and responses in Web APIs using a new, strongly
typed HTTP object model
 Full support for routes
 Web APIs now support the full set of route capabilities that have always been a part of the Web
stack, including route parameters and constraints
 Additionally, mapping to actions has full support for conventions, so no longer need to apply
attributes such as [HttpPost] to your classes and methods
 Filters
 Web APIs now supports filters, including well-known filters such as the [Authorize] attribute
ASP.NET Web API Features
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6.  Content negotiation
 The client and server can work together to determine the right format for data being returned
from an API
 Provide default support for XML, JSON, and Form URL-encoded formats, and extend this support
by adding your own formatters
 Model binding and validation: Model binders provide an easy way to extract data from various
parts of an HTTP request and convert those message parts into .NET objects which can be used
by the Web API actions
 Improved testability of HTTP details
 Rather than setting HTTP details in static context objects, Web API actions can now work with
instances of HttpRequestMessage and HttpResponseMessage
 Generic versions of these objects also exist to work with custom types in addition to the HTTP
types
ASP.NET Web API Features (Cont.)
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7.  Query composition
 By simply returning IQueryable<t>, Web API will support querying via the OData URL
conventions
 Improved Inversion of Control (IoC) via DependencyResolver
 Web API now uses the service locator pattern implemented by MVC’s dependency resolver to
obtain instances for many different facilities
 Code-based configuration
 Web API configuration is accomplished solely through code, leaving config files clean
 Self-host
 Web APIs can be hosted in own process in addition to IIS while still using the full power of routes
and other features of Web API
ASP.NET Web API Features (Cont.)
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8.  The client is whatever consumes the web API (browser, mobile app, and so forth)
 A model is an object that represents the data in application. In this case, the only model is
a to-do item. Models are represented as simple C# classes (POCOs)
 A controller is an object that handles HTTP requests and creates the HTTP response
ASP.NET Web API Design
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9.  MVC : Model -> View -> Controller
 Create a Model
 Create a Controller
ASP.NET MVC Web API
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10.  It is defined, by default, as api/{controller}/{id} where action is defined by an HTTP method
(in global.asax Application_Start method)
Routing Table
HTTP Method URI Path Action Performed
GET /api/products Get All Products
GET /api/products/id Get Product by Id
GET /api/products?category=category Get Products by Category
POST /api/products Insert Product
PUT /api/products/id Update Product
DELETE /api/products/id Delete Product
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11. The four main HTTP methods are mapped to CRUD operations:
 Get retrieves the representation of the resource at a specified URI. GET should have no side
effects on server
 PUT updates a resource at a specified URI
 POST Create a new resource. The server assigns the URI for the new object and returns this URI
as part of the response message
 DELETE deletes a resource at a specified URI
Routing Table
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12. ASP.NET MVC Web API - Example
APIs for crud operation for products
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13.  Response messages, errors and exceptions are translated to HTTP response status codes
 For example:
 POST request should reply with HTTP status 201 (created)
 DELETE request should reply with HTTP status 204 (no content)
 But:
 If a PUT/GET request is done with an invalid id, it should reply with HTTP status 404 (not found)
 Or if a PUT request has invalid model, it can reply with HTTP status 400 (bad request)
Error & Exception Handling
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14.  By default, all .NET exceptions are translated into an HTTP response with status code 500
(internal error)
 It is possible to register Exception filters:
Error & Exception Handling (Cont.)
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15.  Like MVC, Web API supports Data Annotations
(System.ComponentModel.DataAnnotations)
Model Validation
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16. Model Validation - Example
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17.  Create a FilterAttribute
 Add it to Filters in Global.asax Application_Start
Model Validation - FilterAttribute
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18.  https://www.tutorialspoint.com/asp.net_mvc/asp.net_mvc_web_api.htm
 https://www.asp.net/web-api/overview/getting-started-with-aspnet-web-api/tutorial-
your-first-web-api
 http://www.c-sharpcorner.com/uploadfile/4d9083/how-to-create-web-api-in-asp-net-
mvc/
References
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19. Questions?
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