http://www.dotnet-tricks.com/Tutorial/webapi/Y95G050413-Difference-between-ASP.NET-MVC-and-ASP.NET-Web-API.html

• Asp.Net MVC is used to create web applications that returns both views and data but Asp.Net Web API is used to create full blown HTTP services with easy and simple way that returns only data not view.（ASP MVC返回view和数据，Asp.Net Web API只返回数据）

• Web API helps to build REST-ful services over the .NET Framework and it also support content-negotiation(it‘s about deciding the best response format data that could be acceptable by the client. it could be JSON,XML,ATOM or other formatted data), self hosting which are not in MVC.（Web API不同形式的数据，比如xml，json等）

• Web API also takes care of returning data in particular format like JSON,XML or any other based upon the Accept header in the request and you don‘t worry about that. MVC only return data in JSON format using JsonResult.（MVC只能返回json类型的数据）

• In Web API the request are mapped to the actions based on HTTP verbs but in MVC it is mapped to actions name.（Web API的http request会根据谓词来map到具体的action上，而MVC根据action name去map到具体的action上）

• Asp.Net Web API is new framework and part of the core ASP.NET framework. The model binding, filters, routing and others MVC features exist in Web API are different from MVC and exists in the new System.Web.Httpassembly. In MVC, these featues exist with in System.Web.Mvc. Hence Web API can also be used with Asp.Net and as a stand alone service layer.（ASP Web API的各个功能，比如model binding, filters, routing等是在System.Web.Http中实现的，而类似的MVC框架的功能是在System.Web.Mvc中实现的。也就是说Web API和Asp MVC是两套独立的体系）

• You can mix Web API and MVC controller in a single project to handle advanced AJAX requests which may return data in JSON, XML or any others format and building a full blown HTTP service. Typically, this will be called Web API self hosting.（你可以将Web API和MVC在同一个工程中一起使用）

• When you have mixed MVC and Web API controller and you want to implement the authorization then you have to create two filters one for MVC and another for Web API since boths are different.（如果你将Web API controller和MVC controller一起混合使用，在他们需要authorization的时候，你必须为实现各自的authorization机制）

• Moreover, Web API is light weight architecture and except the web application it can also be used with smart phone apps.（Web API是轻量级的架构，可以用在手机程序中）

Asp.Net Web API VS Asp.Net MVC