C# 4 and .NET 4

HTTP Client application ❘ 891
hTTP ClienT aPPliCaTion
The client application can be a simple application to just send HTTP requests to the service and receive
AtomPub or JSON responses. The first client application example is a WPF application that makes use of
the HttpWebRequest class from the System.Net namespace.
Figure 32-2 shows the UI from the Visual Studio Designer. A TextBox named textUrl is used to enter the
HTTP request with a default value of http://localhost:9000/Samples/Menus. The read-only TextBox
named textReturn receives the answer from the service. You can also see a CheckBox checkJSON, where
the response can be requested in the JSON format. The Button with the content Call Data Service has the
Click event associated to the OnRequest() method.
In the implementation of the OnRequest()
handler, an HttpWebRequest object is created
with the WebRequest.Create() factory method.
The HTTP request that is sent is defined by
the textUrl.Text property. If the JSON
checkbox is selected, the Accept property of
the HttpWebRequest is set to application/
json. This way, the data service returns a
JSON response instead of the default AtomPub
format. The request to the server is sent with
the asynchronous method BeginGetResponse.
When a response from the service is received,
the method defined with the first parameter
as a Lambda expression is invoked. The
response is read from a stream associated with
HttpWebResponse, converted to a string, and
passed to the textResult TextBox.
figure 32-2
private void OnRequest(object sender, RoutedEventArgs e)
{
HttpWebRequest request = WebRequest.Create(textUrl.Text)
as HttpWebRequest;
if (checkJSON.IsChecked == true)
{
request.Accept = "application/json";
}
request.BeginGetResponse((ar) =>
{
try
{
using (MemoryStream ms = new MemoryStream())
{
const int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
HttpWebResponse response =
request.EndGetResponse(ar) as HttpWebResponse;
Stream responseStream = response.GetResponseStream();
int count;
while ((count = responseStream.Read(buffer, 0,
bufferSize)) > 0)
{
ms.Write(buffer, 0, count);
}
responseStream.Close();
byte[] dataRead = ms.ToArray();
string data = UnicodeEncoding.ASCII.GetString(
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