Content Negotiation in Web API

One of the standards of the RESTful service is that, the client should have the ability to decide in which format they want the response - XML, JSON etc. A request that is sent to the server includes an Accept header. Using the Accept header the client can specify the format for the response. For example

Accept: application/xml returns XML
Accept: application/json returns JSON

Depending on the Accept header value in the request, the server sends the response. This is called Content Negotiation. 

So what does the Web API do when we request for data in a specific format
The Web API controller generates the data that we want to send to the client. For example, if you have asked for list of employees. The controller generates the list of employees, and hands the data to the Web API pipeline which then looks at the Accept header and depending on the format that the client has requested, Web API will choose the appropriate formatter. For example, if the client has requested for XML data, Web API uses XML formatter. If the client has requested for JSON data, Web API uses JSON formatter. These formatters are called Media type formatters.

ASP.NET Web API is greatly extensible. This means we can also plugin our own formatters, for custom formatting the data.

Multiple values can also be specified for the Accept header. In this case, the server picks the first formatter which is a JSON formatter and formats the data in JSON.
Accept: application/xml,application/json

You can also specify quality factor. In the example below, xml has higher quality factor than json, so the server uses XML formatter and formats the data in XML.
application/xml;q=0.8,application/json;q=0.5

If you don't specify the Accept header, by default the Web API returns JSON data.

ASP.NET Web API - HTTP GET, PUT, POST and DELETE verbs

ASP.NET Web API resource these 4 actions correspond to GET, POST, PUT and DELETE as shown in the table below 

CRUD	HTTP Verb
Create	POST
Read	GET
Update	PUT
Delete	DELETE

Request Verbs : These HTTP verbs (GET, POST, PUT & DELETE) describe what should be done with the resource. For example do you want to create, read, update or delete an entity. GET, PUT, POST and DELETE http verbs are the most commonly used one's. For the complete list of the HTTP verbs, please check http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html

Request Header : When a client sends request to the server, the request contains a header and a body. The request header contains additional information such as what type of response is required. For example, do you want the response to be in XML or JSON.

Request Body : Request Body contains the data to send to the server. For example, a POST request contains the data for the new item that you want to create. The data format may be in XML or JSON.

Response Status codes : These are the HTTP status codes, that give the client details on the status of the request. Some of the common status codes are 200/OK, 404/Not Found, 204/No Content. For the complete list of HTTP status codes and what they mean, please visit http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html

Authorization has been denied for this request - New Web API Project

<Error>
    <Message>Authorization has been denied for this request.</Message>
</Error>



accept

In the ValuesController there is an attribute Authorize if you remove it, then it will work as home page.

The Authorize attribute just prevent an anonymous users from accessing the ValuesController.

to work with this attribute, you need first to register a user, and then login to get user's token, then you can use the token to authorize your self and get access