Streaming over HTTP with WCF

Recently I had a customer email me looking for information on how to send and receive large files with a WCF HTTP service. WCF supports streaming specifically for these types of scenarios.  Basically with streaming support you can create a service operation which receives a stream as it’s incoming parameter and returns a stream as it’s return value (a few other types like Message and anything implementing IXmlSerializable are also supported). MSDN describes how streaming in WCF works here, and how to implement it here. There’s a few gotchas however if you are dealing with sending large content with a service that is hosted in ASP.NET. If you scour the web you can find the answers, such as in the comments here.

In this post I’ll bring everything together and walk you through building a service exposed over HTTP and which uses WCF streaming. I’ll also touch on supporting file uploads with ASP.NET MVC, something I am sure many are familiar with. The sample which we will discuss requires .NET 4.0 and ASP.NET MVC 3 RC. If you don’t have MVC you can skip right to the section “Enabling streaming in WCF”. Also it’s very easy to adopt the code to work for web forms.

The scenario
For the sample we’re going to use a document store. To keep things simple and stay focused on the streaming, the store allows you to do two things, post documents and retrieve them through over HTTP. Exposing over HTTP means I can use multiple clients/devices to talk to the repo.  Here are more detailed requirements.

1. A user can POST documents to the repository with the uri indicating the location where the document will be stored using the uri format “http://localhost:8000/documents/{file}”. File in this case can include folder information, for example the following is a valid uri, “ ”.

Below is what the full request looks like in Fiddler. Note: You’ll notice that the uri (and several below) has a “.” in it after localhost, this is a trick to get Fiddler to pick up the request as I am running in Cassini (Visual Studio’s web server).

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