Web API Basics

							Web API Basics




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Objectives
• See how REST and web services can be used to
  access data
• Build your first Web API service
• Use Web API naming conventions for routing
• Modify your service for basic CRUD operations
• Filter your data results with URL parameters


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Agenda
•   What Is ASP.NET Web API?
•   Create Your First Web API Service
•   Web API Routing
•   Create a Web API Service for CRUD Operations
•   Filtering Data with Parameters




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What Is ASP.NET Web API?
• Next iteration of WCF REST
• Incorporated into ASP.NET MVC 4
• Framework for developing REST oriented
  services




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REST
•   Uses HTTP protocols
•   URLs and methods
•   Accessible from a wide variety of clients
•   HTTP methods:
    • GET
    • POST
    • PUT
    • DELETE


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GET
• Primarily just a URL making a simple request for a
  resource, e.g., a web page
• Response is sent back
• Additional information is put in a query string
• Generally used to Select data
• Selecting all:
• http://www.root.com/products/
• Selecting one:
• http://www.root.com/products/17

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POST
• Sends collection of name-value pairs along
  with the request
• Commonly used with forms on the web
• Used to add new resources (Insert)
• Should return an appropriate HTTP success
  code



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PUT
• Used to store a resource at the supplied URL
• Generally used for Editing existing resources




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DELETE
• Used for deleting resources
• Should return an appropriate HTTP code




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Agenda
•   What Is ASP.NET Web API?
•   Create Your First Web API Service
•   Web API Routing
•   Create a Web API Service for CRUD Operations
•   Filtering Data with Parameters




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Create Your First Web API Service
 • Create a repository
 • Create an API controller to use the repository
 • Try it out in a browser




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Agenda
•   What Is ASP.NET Web API?
•   Create Your First Web API Service
•   Web API Routing
•   Create a Web API Service for CRUD Operations
•   Filtering Data with Parameters




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                Copyright © by Application Developers Training Company
Web API Routing
• Interpretation of URLs by the server to decide
  what code should handle the request
• Operates similarly to ASP.NET MVC routing
• Actions determined by HTTP method used




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Default Mapping
• Configured in Global.asax
• Uses “api” as URL segment
• Adds word “Controller” to the controller part
  of URL
• Looks for action that begins with the HTTP
  method
• Additional URL parameters are mapped as
  action parameters

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Alternative Routing Conventions
• Rarely necessary for most Web API services
• Several options to change URL routing




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HTTP Method Attributes
• Very similar to ASP.NET MVC
• Use attributes to bind HTTP methods to
  specific actions
• [HttpGet]
• [HttpPost]
• [HttpPut]
• [HttpDelete]

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AcceptVerbs Attribute
• Also used on actions
• Specify HTTP methods as strings
• Especially useful for atypical HTTP methods




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Action Names in the URL
• Makes URLs route identically to ASP.NET MVC
• Must change routeTemplate in Global.asax
• Must also add HTTP method attributes to
  actions




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Removing Actions from Routing
• Used when a resource’s URL would trigger an
  action, but this is not desired
• Use the NonAction attribute on the method




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Agenda
• What Is ASP.NET Web API?
• Create Your First Web API Service
• Web API Routing
• Create a Web API Service for CRUD
  Operations
• Filtering Data with Parameters


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             Copyright © by Application Developers Training Company
Create a Web API Service for CRUD
Operations

 •   Create – POST
 •   Read – GET
 •   Update – PUT
 •   Delete – DELETE
 •   Basic functionality that most services will have
 •   Try it out!


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                Copyright © by Application Developers Training Company
Agenda
•   What Is ASP.NET Web API?
•   Create Your First Web API Service
•   Web API Routing
•   Create a Web API Service for CRUD Operations
•   Filtering Data with Parameters




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                Copyright © by Application Developers Training Company
Filtering Data with Parameters
• Uses the OData protocol
• Special query strings can be used to:
  • Filter
  • Page
  • Sort
  • And more…




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Filter
• Condition that evaluates to true or false
• Uses OData-specific keywords
• Must be sendable in a URL




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Order By
• Specifies the sort order of returned data
• Can sort by multiple properties
• Can specify ASC and DESC sorting




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Paging
• Done by using $skip and $top
• $skip passes over a number of records
• $skip should be set to: page number * page
  size
• $top selects a certain number to return
• $top should be set to page size


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There’s More
• There are other OData query strings
• Other query keywords for $filter
• www.odata.org




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Learn More!
• This is an excerpt from a larger course. Visit
  www.learnnowonline.com for the full details!




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