Asp.net web api

Editor's Notes

• #3: ASP.NET Web API is a framework for building HTTP services that can be accessed from any client including browsers and mobile devices. It is an ideal platform for building RESTful applications on the .NET Framework. Before we understand what is Web API, let's see what is an API (Application Programing Interface).
• #4: As per Wikipedia's Definition of API: In computer programming, an application programming interface (API) is a set of subroutine definitions, protocols, and tools for building software and applications. To put it in simple terms, API is some kind of interface which has a set of functions that allow programmers to access specific features or data of an application, operating system or other services.
• #5: It works more or less the same way as ASP.NET MVC web application except that it sends data as a response instead of html view. It is like a webservice or WCF service but the exception is that it only supports HTTP protocol.
• #6: It works more or less the same way as ASP.NET MVC web application except that it sends data as a response instead of html view. It is like a webservice or WCF service but the exception is that it only supports HTTP protocol.
• #13: In a typical console application in C#, execution starts from the Main() function. The Main() function controls the flow of a program or in other words sequence of user interaction. Consider the following simple console program In the above example, the Main() function of the program class controls the flow of a program. It takes user's input for the first Name and last name. It saves the data, continues or exits the console depending upon the user's input. So here, flow of the control through the Main() function.
• #15: Fiddler Postman
• #17: Web API controller is a class which can be created under the Controllers folder or any other folder under your project's root folder. The name of a controller class must end with "Controller" and it must be derived from System.Web.Http.ApiController class. All the public methods of the controller are called action methods.
• #19: If you want to write methods that do not start with an HTTP verb then you can apply the appropriate http verb attribute on the method such as HttpGet, HttpPost, HttpPut etc. same as MVC controller.
• #33: In the above example, School route is configured before DefaultApi route. So any incoming request will be matched with the School route first and if incoming request url does not match with it then only it will be matched with DefaultApi route. For example, request url is http://localhost:1234/api/myschool is matched with School route template, so it will be handled by SchoolController.
• #35: In the above example, the Route attribute defines new route "api/student/names" which will be handled by the Get() action method of StudentController. Thus, an HTTP GET request http://localhost:1234/api/student/names will return list of student names.
• #36: By default, if parameter type is of .NET primitive type such as int, bool, double, string, GUID, DateTime, decimal or any other type that can be converted from string type then it sets the value of a parameter from the query string. And if the parameter type is complex type then Web API tries to get the value from request body by default.
• #38: As you can see above Get action method includes id parameter of int type. So, Web API will try to extract the value of id from the query string of requested URL, convert it into int and assign it to id parameter of Get action method. For example, if an HTTP request is http://localhost/api/student?id=1 then value of id parameter will be 1. Followings are valid HTTP GET Requests for the above action method. http://localhost/api/student?id=1 http://localhost/api/student?ID=1
• #40: As you can see above, Post() action method includes primitive type parameters id and name. So, by default, Web API will get values from the query string. For example, if an HTTP POST request is http://localhost/api/student?id=1&name=steve then the value of id will be 1 and name will be "steve" in the above Post() method.
• #41: Web API will extract the JSON object from the Request body above and convert it into Student object automatically because names of JSON object properties matches with the name of Student class properties (case-insensitive).
• #42: The above Post method includes both primitive and complex type parameter. So, by default , Web API will get the id parameter from query string and student parameter from the request body.
• #43: The above Post method includes both primitive and complex type parameter. So, by default , Web API will get the id parameter from query string and student parameter from the request body. Parameter binding for Put and Patch method will be the same as Post method in Web API.
• #44: By default, if parameter type is of .NET primitive type such as int, bool, double, string, GUID, DateTime, decimal or any other type that can be converted from string type then it sets the value of a parameter from the query string. And if the parameter type is complex type then Web API tries to get the value from request body by default.
• #45: In the above example, Get method includes complex type parameter with [FromUri] attribute. So, Web API will try to get the value of Student type parameter from the query string. For example, if an HTTP GET request http://localhost:xxxx/api/student?id=1&name=steve then Web API will create Student object and set its id and name property values to the value of id and name query string
• #46: As you can see above, we have applied [FromUri] attribute with the Student parameter. Web API by default extracts the value of complex type from request body but here we have applied [FromUri] attribute. So now, Web API will extract the value of Student properties from the query string instead of request body.
• #53: Primitive or Complex Type An action method can return primitive or other custom complex types as other normal methods.
• #54: As you can see above, GetId action method returns an integer and GetStudent action method returns a Student type. An HTTP GET request http://localhost:xxxx/api/student?name=john will return following response in Fiddler. Primitive Return Type in Response
• #55: An HTTP GET request http://localhost:xxxx/api/student?id=1 will return following response in Fiddler.
• #57: As you can see in the above figure, the Web API controller returns HttpResponseMessage object. You can also create and return an object of HttpResponseMessage directly from an action method. The advantage of sending HttpResponseMessage from an action method is that you can configure a response your way. You can set the status code, content or error message (if any) as per your requirement.
• #61: You can create your own class that implements IHttpActionResult or use various methods of ApiController class that returns an object that implement the IHttpActionResult.
• #69: Web API converts request data into CLR object and also serialize CLR object into response data based on Accept and Content-Type headers. Web API includes built-in support for JSON, XML, BSON, and form-urlencoded data. It means it automatically converts request/response data into these formats OOB (out-of the box).
• #70: As you can see above, the Post() action method accepts Student type parameter, saves that student into DB and returns inserted student with generated id. The above Web API handles HTTP POST request with JSON or XML data and parses it to a Student object based on Content-Type header value and the same way it converts insertedStudent object into JSON or XML based on Accept header value.
• #80: Internally, JsonMediaTypeFormatter uses third-party open source library called Json.NETto perform serialization.
• #81: JSON formatter can be configured in WebApiConfig class. The JsonMediaTypeFormatter class includes various properties and methods using which you can customize JSON serialization. For example, Web API writes JSON property names with PascalCase by default. To write JSON property names with camelCase, set the CamelCasePropertyNamesContractResolver on the serializer settings as shown below.
• #83: Filters are actually attributes that can be applied on the Web API controller or one or more action methods. Every filter attribute class must implement IFilter interface included in System.Web.Http.Filters namespace. However, System.Web.Http.Filters includes other interfaces and classes that can be used to create filter for specific purpose.