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Write live stream to response in WCF

I couldn't find an exact example of what I'm looking for.
I have a REST/WCF endpoint that takes in a Stream and returns a Stream. I am able to do "live" streaming of the request, by that I mean that the incoming stream gets read by the service as it is written to by the client (using a shared buffer stream in the service).
I would like to achieve the same thing on the outgoing stream but all the examples I found write all the data to a local stream then return it back to the client.
How can I access the underlying stream of the response and start writing to it, allowing the client to start reading from it without exiting my service method?
Is it even possible to achieve what I need with WCF and HTTP streaming?

How to return both stream and file length from WCF Restful json webservice?

Hihi all,
I am able to return stream from my WCF restful json webservice, everything works fine. But when I mixed the stream with another piece of data (both wrap into a custom class), upon consuming the webservice from my client, it gives an error message of "An existing connection was forcibly closed by the remote host".
Any advice how can I achieve the above? What it's required for my webservice is to allow downloading of a file with the file length as an additional piece of information for validation at the client end.
Thanks in advance! :)

There are various restrictions while using Stream in WCF service contracts - as per this MDSN link, only one (output) parameter or return value (of type stream) can be used while streaming.
In another MSDN documentation (this is anyway a good resource, if you want to stream large data using WCF), it has been hinted that one can combine stream and some input/output data by using Message Contract.
For example, see this blog post where author has used explicit message contract to upload both file name & file data. You have to do the similar thing from download perspective.
Finally, if nothing works then you can always push the file length as a custom (or standard such as content-length) HTTP header. If you are hosting in IIS then enable ASP.NET compatibility and use HttpContext.Current.Response to add your custom header.

SoapHttpClientProtocol: get response as a stream instead of a string?

I'm using a webservice which spits out very large amounts of data in one piece. The response string can be something like 8MB. While not an issue on a desktop PC, an embedded device goes nuts dealing with an 8MB string object.
I wonder if there is a way to get the response as a stream? Currently I'm using the method like below. I tried using a POST request instead, but SOAP is just more convenient (the response is XML and with the POST I have to convert the plain text reply back to valid XML) and I'd like to stick with it. Is it possible to use a different kind of "Invoke" which won't return strings but streams? Any ideas?
[System.Web.Services.Protocols.SoapDocumentMethodAttribute("MyAPI/MyMethod", RequestNamespace="MyAPI", ResponseNamespace="MyAPI", ParameterStyle=System.Web.Services.Protocols.SoapParameterStyle.Wrapped, Use=System.Web.Services.Description.SoapBindingUse.Literal)]
public string MyMethod(string sID)
{
object[] results = this.Invoke("MyMethod", new object[] { sID });
return ((string)(results[0]));
}

If you use the old ASMX web service client infrastructure, then you're stuck with its limitations. One limitation is that there's no simple way to get the response except as deserialized data.
If it were necessary, then you could use a partial class to override the GetWebResponse method to return your own custom WebResponse. This latter would in turn override the GetResponseStream method to call the base version, consume the stream, then to return a stream containing an "empty" web request (otherwise .NET will choke on a stream with no contents).
You might also try something similar by overriding the GetReaderForMessage method. This is passed a SoapClientMessage instance which has a Stream property that you might be able to use. Again, you'll have to set the stream to something that the web service infrastructure can consume.
The better way to do this is with a WCF client. WCF has much more powerful and easy to use extensibility mechanisms.
In fact, you might not even need to extend a WCF client. You might simply be able to configure it to not have this buffering problem at all.

Any web service call is going to return SOAP, isn't it? I don't think a stream could be serialized into a soap packet to be returned from your service. And even if it could, wouldn't the serialized stream be at least as big as the string itself?

I believe the answer is no, there is no concept of a stream for SOAP.
Probably the simplest answer is to have your method:
Parse your response into segments your mobile device can handle
Cache your response in a application variable as a dictionary of these segments
return an arraylist of GUIDs.
You can then have your client request each of these segments separately via their GUIDs, then reassemble the original response when and handle it all the web services return.

ASMX can't do much about this. WCF's BasicHttpBinding can return a Stream to the caller.
http://msdn.microsoft.com/en-us/library/ms733742.aspx

Operate on HTTP Request as it is received in IIS in C#

I have a need to override the receipt of a raw HTTP request as it is being communicated to an IIS server. I want to know if this is possible.
We have a client who sends huge Web Service calls (tens of Mb) and we want to start acting on portions of those calls as they are being received (in order to get a faster total time of execution for the Web Service call).
Currently, using normal web service methods, our application code is handed the Web Service call after it is totally received.
I realize this isn't the ideal way of handling Web Services, and we're not building our business on this, but we do have an need that we're trying to fill for a limited range of customers.
I have created a handler that implements IHttpHandler, but it appears that at this point in the process pipeline, the Request has been fully received by IIS (which doesn't get us any benefit over our current model). That is, I can read the InputStream directly, but the full request has already been transferred over the wire before I have access to this stream.
I think the answer is that I have to code an ISAPI filter to get this far down, but I don't have the skills to do this in C/C++. Does anyone know if there's another way I can do this without the ISAPI filter route?
An acceptable answer could be, "You have to do this as and ISAPI filter, to do it in C#, check this doc".

You can use a custom HttpModule to hook almost any part of the IIS pipeline. They work in both IIS 6 (under ASP.NET) and are the primary extension mechanism in IIS 7.

There are plenty of examples of building ISAPI filters, but none in C#. I am sure it is possible, but not practical and not without lots dirty tricks.
Your C# investment will hold up well in C++, let me know if you need help. By the way, I recommend you invest in the my standard trio - try to keep up a healthy knowledge of C#, C++ and Java.
I also recommend you consider Apache modules, they may offer more overall flexibility. This is what I would do:
host these web services off of IIS - you never know when IIS will bite you by resetting the application.
Use WCF services, host these from Windows services, use redirection to route the service to the WCF service.
Consider writting a raw sockets application. This one would implement the minimal WS:* protocol to your service and act as a proxy for the real service. When the proxy detects that the inbound message is exceeding a threshold it would begin analyzing the message to extract out what it could process right away.
The result would be standard WCF (through proxy) for smaller messages and non-standard processing for everything else.
Let me know if I can help you build it - this is the kind of thing I like to do...
Oh - and I recall now that WCF is completely configurable. You will be able to provide your own handlers for a variaty of layers and resolve everything from within managed code after all.

Short Version
The solution is to use HttpRequest.GetBufferlessInputStream.
Long Version
The issue is that if you attempt to use:
Request.InputStream
or Request.Form
or Request.Files
you must wait until the whole request has been received before it returns a Stream object. In contrast, the GetBufferlessInputStream method returns the Stream object immediately. You can use the method to begin processing the entity body before the complete contents of the body have been received.
This method can be useful if the request is uploading a large file and you want to begin accessing the file contents before the upload is finished. However, you should only use this method for scenarios where you want to take over all processing of the entity body. This means that you cannot use this method from an .aspx page, because by the time an .aspx page runs, the entity body has already been read.
The only downside, and it is a huge downside, is that you are now reading the Request.InputStream. This means you have to handle the MIME multiparts, and the base64 encoding, yourself.
Example (untested) code
UploadFile.ashx
public class Default : IHttpHandler
{
public void ProcessRequest (HttpContext context)
{
var request = context.Request;
var stm = request.GetBufferlessInputStream(true); //true --> disable web.config limits on request size
if (!stm.CanRead)
throw new Exception("Request input stream is not readable");
//Setup the buffer we'll be shuffling stream data into
int bufferLength = 16 * 8040; //use a multiple of 8040 bytes, because SQL Server uses pages of 8040 bytes. And because i'm saving it into SQL Server.
byte[] buffer = new Byte[bufferLength];
int bytesRead;
bytesRead = stm.Read(buffer, 0, buffer.Length);
while (bytesRead > 0)
{
SavePiece(buffer, bytesRead); //whatever you want to do with it
bytesRead = stm.Read(buffer, 0, buffer.Length);
}
}
private void SavePiece(byte[] buffer, int bufferLength)
{
//It's all going to be multipart mime encoded nonsense.
//Good luck!
}
public bool IsReusable { get { return false;}
}
Bonus Reading
How can I decode a multipart HTTP response?
Are there any multipart/form-data parser in C# - (NO ASP)
https://stackoverflow.com/a/21689347/12597 (example usage of the StreamContent class in .NET)
MSDN: StreamContent Class

Does WCF automatically URL encode/decode streams?

I'm programming a service for a program that uses HTTP post/get requests, so I handle all incoming requests with a hook method that takes a System.IO.Stream and returns a System.IO.Stream.
When I parse the incoming request (contained in an HTML form) by converting to a string and then using System.Web.HttpUtility.ParseQueryString(string), it seems to automatically URL-decode the data. When I return a file path (a Windows UNC, not going to explain why I do that), I initially URL-encoded the string before converting to a stream and returning it using a return-statement, the client seems to get a doubly-coded string.
So, just to be sure, does WCF automatically URL encode/decode streams for me as part of using System.ServiceModel.WebHttpBinding?

Apparently, it does:
"For RESTful services, WCF provides a binding named System.ServiceModel.WebHttpBinding.
This binding includes pieces that know how to read and write information using the HTTP and HTTPS transports, as well as encode messages suitable for use with HTTP."
from here.