TrustArc Webinar - Unlock the Power of AI-Driven Data Discovery
ASP.NET Web API
1.
2. Contents
What & Why ASP.NET Web API
A look at Rest & Soap
Basic Web API Structure
Web API Routing & Actions
Validation
Odata
Content Negotiation
Http Client
3. ASP.NET Web API
ASP.NET Web API is a framework for building http
based services in top of .net framework.
WCF Care about transport flexibility.
WebAPI Care about HTTP
5. Reach more clients
Client appropriate format
Embrace http
Use http as an application protocol
Amazon has both Rest and Soap based services
and 85% of the usage is Rest based.
6.
7. SOAP
A specification
Rest
A set of architectural principal
Resource Oriented Architecture
Resources
Their names(URIs)
Uniform Intercace
8.
9.
10. Asmx
Ws*
Wcf
Wcf 3.5
Wcf rest starter kit
Wcf Rest service
ASP.Net Web API
11. Web API - 1 slide
public class ValueController : ApiController
{
// GET <controller>
public string Get()
{
return "Demo result at " + DateTime.Now.ToString();
}
}
protected void Application_Start(object sender, EventArgs e)
{
GlobalConfiguration.Configuration.Routes.Add("default",
new HttpRoute("{controller}"));
}
16. Routing and Actions
Web API uses the HTTP method, not the URI path,
to select the action.
To determine which action to invoke, the framework
uses a routing table.
routes.MapHttpRoute(
name: "API Default",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
17. If no route matches, the client receives a 404 error.
Custom name mapping to http actions.
[HttpGet]
public Product FindProduct(id) {}
18. or can override the action name by using
the ActionName attribute.
api/products/thumbnail/id
[HttpGet]
[ActionName("Thumbnail")]
public HttpResponseMessage
GetThumbnailImage(int id);
19. To prevent a method from getting invoked as an
action, use the NonAction attribute.
// Not an action method.
[NonAction]
public string GetPrivateData() { ... }
20. Exception Handling
By default, most exceptions are translated into an HTTP response
with status code 500, Internal Server Error.
public Product GetProduct(int id)
{
Product item = repository.Get(id);
if (item == null)
{
var resp = new
HttpResponseMessage(HttpStatusCode.NotFound)
{
Content = new StringContent(string.Format("No product with ID
= {0}", id)),
}
throw new HttpResponseException(resp);
}
return item;
}
21. HTTP/1.1 404 Not Found
Content-Type: application/json; charset=utf-8
Date: Thu, 09 Aug 2012 23:27:18 GMT
Content-Length: 51
{
"Message": “No product with id = 12 not found"
}
22. You can customize how Web API handles exceptions by
writing an exception filter.
public class NotImplExceptionFilterAttribute :
ExceptionFilterAttribute
{
public override void
OnException(HttpActionExecutedContext context)
{
if (context.Exception is NotImplementedException)
{
context.Response = new
HttpResponseMessage(HttpStatusCode.NotImplemented);
}
}
}
23. There are several ways to register a Web API
exception filter:
By action
By controller
Globally
[NotImplExceptionFilter]
GlobalConfiguration.Configuration.Filters.Add(
new
ProductStore.NotImplExceptionFilterAttribute());
24. Validation
public class Product
{
public int Id { get; set; }
[Required]
public string Name { get; set; }
public decimal Price { get; set; }
[Range(0,999)]
public double Weight { get; set; }
}
25. if (ModelState.IsValid)
{
return new
HttpResponseMessage(HttpStatusCode.OK);
}
else
{
return new
HttpResponseMessage(HttpStatusCode.BadReques
t);
}
26. public class ModelValidationFilterAttribute : ActionFilterAttribute
{
public override void OnActionExecuting(HttpActionContext actionContext)
{
if (actionContext.ModelState.IsValid == false)
{
var errors = new Dictionary<string, IEnumerable<string>>();
foreach (KeyValuePair<string, ModelState> keyValue in
actionContext.ModelState)
{
errors[keyValue.Key] = keyValue.Value.Errors.Select(e =>
e.ErrorMessage);
}
actionContext.Response =
actionContext.Request.CreateResponse(HttpStatusCode.BadReq
uest, errors);
}
}
}
27. HTTP/1.1 400 Bad Request
Server: ASP.NET Development Server/10.0.0.0
Date: Fri, 20 Jul 2012 21:42:18 GMT
Content-Type: application/json; charset=utf-8
Content-Length: 239
Connection: Close
{
"product": [
"Required property 'Name' not found in JSON. Line 1, position 18."
],
"product.Name": [
"The Name field is required."
],
"product.Weight": [
"The field Weight must be between 0 and 999."
]
}
29. public class Product
{
public string Name { get; set; }
public decimal Price { get; set; }
[JsonIgnore]
public int ProductCode { get; set; } // omitted
}
30. [DataContract]
public class Product
{
[DataMember]
public string Name { get; set; }
[DataMember]
public decimal Price { get; set; }
public int ProductCode { get; set; } // omitted by
default
}
32. Option Description
$filter
Filters the results, based on a Boolean
condition.
$inlinecount
Tells the server to include the total count
of matching entities in the response.
(Useful for server-side paging.)
$orderby Sorts the results.
$skip Skips the first n results.
$top Returns only the first n the results.
:
35. Content Negotiation
The process of selecting the best representation for
a given response when there are multiple
representations available.
Accept:
Accept-Charset:
Accept-Language:
Accept-Encoding:
36. HttpClient
HttpClient is a modern HTTP client for ASP.NET Web
API. It provides a flexible and extensible API for
accessing all things exposed through HTTP.
HttpClient is the main class for sending and
receiving HttpRequestMessages and
HttpResponseMessages.
Task based pattern
Same HttpClient instance can be used for multiple
URIs even from different domains.
