Working with http

Working with HTTP

Eyal Vardi
CEO E4D Solutions LTD
Microsoft MVP Visual C#
blog: www.eVardi.com

Expert Days 2012


© 2010 E4D LTD. All rights reserved. Tel: 054-5-767-300, Email: Eyal@E4D.co.il

Agenda
 HTTP Message Handlers

 Self Hosting

 Sending HTML Form Data
 Form-urlencoded Data

 File Upload and Multipart MIME


HTTP Message Handlers
 ASP.NET Web API has a pipeline for
processing HTTP messages on both the client
and server.
 HttpRequestMessage

 HttpResponseMessage

 HttpMessageHandler
objects process the request and response


.NET Client
 .Net application can use the HttpClient class
to send HTTP requests.
 HttpClient sends the request to a message
handler. The message handler returns an
HttpResponseMessage.
Abstract


HttpClientHandler Class
 HttpClient by default uses the HttpClientHandler
class.
 This class is a message handler that converts the
HttpRequestMessage into an HTTP request, sends the HTTP
request over the network, and converts the HTTP response
into an HttpResponseMessage.


Custom Message Handler for
HttpClient

CMH

CMH

CMH


.NET Client


Server Message Handlers
 HttpServer derives from HttpMessageHandler.
 The request then passes through a series of message
handlers.

 HttpControllerDispatcher handler uses the
routing table to route the request to a Web API
controller. CMH

CMH


Custom Message Handlers
 Process the request message.
 Call base.SendAsync to send the message to
the inner handler. This step is asynchronous.
 Process the response message and return it
to the caller.

Task<HttpResponseMessage> SendAsync(
HttpRequestMessage request,
CancellationToken cancellationToken);


Custom Response Header
public class CustomHeaderHandler : DelegatingHandler
{
protected override Task<HttpResponseMessage> SendAsync(
HttpRequestMessage request, CancellationToken cancellationToken)
{
return base.SendAsync(request, cancellationToken)
.ContinueWith(
(task) =>
{
HttpResponseMessage response = task.Result;
response.Headers.Add(
"X-Custom-Header",
"This is my custom header.");
return response;
}
);
}
}


Adding CMH in Server Side
 On the server side, add custom message
handlers to the MessageHandlers collection
on the HttpConfiguration object.
 Message handlers are called in the reverse
order of the MessageHandlers collection.
public static class WebApiConfig
{
public static void Register(HttpConfiguration config) Last
{
config.MessageHandlers.Add(new MethodOverrideHandler());
config.MessageHandlers.Add(new CustomHeaderHandler());
config.MessageHandlers.Add(new ApiKeyHandler("secret"));

// Other code not shown... First
}
}


Adding CMH in Client Side
 Pass the outer message handler in the
HttpClient constructor.
 To chain more than one message handler, you
must set the InnerHandler property of each
message handler in the chain.

var handler = new CustomHeaderHandler()
{
InnerHandler = new HttpClientHandler()
};

HttpClient client = new HttpClient(handler);


HTTP Request in Memory
 Because HttpServer is a message handler,
you can plug it directly into the HttpClient
class.

var config = new HttpConfiguration();
config.Routes.MapHttpRoute(
"default",
"api/{controller}/{id}",
new { id = RouteParameter.Optional });

HttpServer server = new HttpServer(config);

// Connect client directly to server
HttpClient client = new HttpClient(server);

var response = client.GetAsync("http://anything/api/products").Result;


Custom Message
Handlers


Self Host Config


Self Host
var config = new HttpSelfHostConfiguration("http://localhost:8080");

config.Routes.MapHttpRoute(
"API Default", "api/{controller}/{id}",
new { id = RouteParameter.Optional });

using (HttpSelfHostServer server = new HttpSelfHostServer(config))
{
server.OpenAsync().Wait();
Console.ReadLine();
}


Sending HTML Form Data


Enctype Attribute in Form Tag
 The enctype attribute specifies the format of
the request body:

enctype Description

application/x-www- Form data is encoded as name/value pairs, similar to a
form-urlencoded URI query string. This is the default format for POST.

Form data is encoded as a multipart MIME message. Use
multipart/form-data
this format if you are uploading a file to the server.


<h1>Complex Type</h1>
<form id="form1" method="post" action="api/updates/complex"
enctype="application/x-www-form-urlencoded">
<div>
<label for="status">Status</label>
</div>
<div>
<input name="status" type="text" />
</div>
<div>
<label for="date">Date</label>
</div>
<div>
<input name="date" type="text" />
</div>
<div>
<input type="submit" value="Submit" />
POST http://localhost:38899/api/updates/complex HTTP/1.1
</div>
Accept: text/html, application/xhtml+xml, */*
</form>
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; WOW64;
Trident/5.0)
Content-Type: application/x-www-form-urlencoded
Content-Length: 47

status=Shopping+at+the+mall.&date=6%2F15%2F2012


Sending Form Data via AJAX
<script type="text/javascript">
$("#form1").submit(function () {
var jqxhr = $.post('api/updates/complex', $('#form1').serialize())
.success(function () {
var loc = jqxhr.getResponseHeader('Location');
var a = $('<a/>', { href: loc, text: loc });
$('#message').html(a);
})
.error(function () {
$('#message').html("Error posting the update.");
});
return false;
});
</script>


File Upload and Multipart MIME
 When a form contains a file input control, the
enctype attribute should always be
"multipart/form-data".
<form name="form1" method="post" enctype="multipart/form-data" action="api/upload">
<div>
<label for="caption">Image Caption</label>
<input name="caption" type="text" />
</div>
<div>
<label for="image1">Image File</label>
<input name="image1" type="file" />
</div>
<div>
<input type="submit" value="Submit" />
</div>
</form>


File Upload


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