WCF + REST: Where is the request data? - wcf

Question

I'm currently developing a WCF RESTful service. Within the validation of the POST data, I am throwing exceptions if the request XML does not conform to our business rules.
The goal is to send an e-mail to the appropriate staff if a request comes in that considered invalid. But, along with the incoming request headers, method and URI, I'd like to also send the XML that was posted.
I have not been able to find a way to access this data. Is WCF actually destroying the request body/data before I have a chance to access it or am I missing something?
Your help is appreciated as I'm confused as to why I can't access the request data.

Answer 1

This unfortunately isn't supported- we had a similar need, and did it by calling internal members with reflection. We just use it in an error handler (so we can dump the raw request), but it works OK. I wouldn't recommend it for a system you don't own and operate though (eg, don't ship this code to a customer), since it can change at any time with a service pack or whatever.
public static string GetRequestBody()
{
OperationContext oc = OperationContext.Current;
if (oc == null)
throw new Exception("No ambient OperationContext.");
MessageEncoder encoder = oc.IncomingMessageProperties.Encoder;
string contentType = encoder.ContentType;
Match match = re.Match(contentType);
if (!match.Success)
throw new Exception("Failed to extract character set from request content type: " + contentType);
string characterSet = match.Groups[1].Value;
object bufferedMessage = operationContextType.InvokeMember("request",
BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.GetField,
null, oc, null);
//TypeUtility.AssertType(bufferedMessageType, bufferedMessage);
object messageData = bufferedMessageType.InvokeMember("MessageData",
BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.GetProperty,
null, bufferedMessage, null);
//TypeUtility.AssertType(jsonBufferedMessageDataType, messageData);
object buffer = jsonBufferedMessageDataType.InvokeMember("Buffer",
BindingFlags.Instance | BindingFlags.Public | BindingFlags.GetProperty,
null, messageData, null);
ArraySegment<byte> arrayBuffer = (ArraySegment<byte>)buffer;
Encoding encoding = Encoding.GetEncoding(characterSet);
string requestMessage = encoding.GetString(arrayBuffer.Array, arrayBuffer.Offset, arrayBuffer.Count);
return requestMessage;
}

Answer 2

So, if you declare your contract something like:
[WebInvoke(Method = "POST", UriTemplate = "create", ResponseFormat=WebMessageFormat.Json)]
int CreateItem(Stream streamOfData);
(you can use XML instead)
The streamOfData should be the body of an HTTP POST. You can deserialize it using something like:
StreamReader reader = new StreamReader(streamId);
String res = reader.ReadToEnd();
NameValueCollection coll = HttpUtility.ParseQueryString(res);
It's working like that for us, at least. You may want to use a different approach to get the string into an XMLDocument or something. This works for our JSON posts. Might not be the most elegant solution, but it is working.
I hope this helps.
Glenn

Answer 3

Try this,
OperationContext.Current.RequestContext.RequestMessage

Answer 4

Here's how you do it without reflection:
using (var reader = OperationContext.Current.RequestContext.RequestMessage.GetReaderAtBodyContents ()) {
if (reader.Read ())
return new string (Encoding.ASCII.GetChars (reader.ReadContentAsBase64 ()));
return result;
}
}
If the reader is a HttpStreamXmlDictionaryReader (as it was in my case), the class's implementation of the method ReadContentAsBase64(byte[] buffer, int index, int count) simply passes these parameters to the Stream.Read method.
Once I have the byte[] I convert the bytes to a string via ASCII encoding. For a proper implementation, you could use the content type & encoding from the message's headers to do per HTTP spec.

Answer 5

You could arrest the HttpApplication.Request.InputStream in a custom HttpModule of the WCF Service, read the stream and again set its position to 0 in the custom HttpModule's event handler. Then store it in session and access it further in the actual OperationContract.
For example:
public class CustomModule : IHttpModule
{
public void Dispose()
{
}
public void Init(HttpApplication context)
{
context.AcquireRequestState +=context_AcquireRequestState;
}
void context_AcquireRequestState(object sender, EventArgs e)
{
HttpApplication application = sender as HttpApplication;
Stream str = application.Request.InputStream;
StreamReader sr = new StreamReader(str);
string req = sr.ReadToEnd();
str.Position = 0;
application.Session["CurrentRequest"] = req;
}
}