A while ago i had to modify an existing WCF REST service which was being consumed by BITS. Apparently the implementation has changed in Windows7 in such a way that the BITS client first makes a HEAD request to discover the file size.
The following attempts did not work:
// A method can not have both WebGet and WebInvoke attributes
[OperationContract]
[WebGet]
[WebInvoke(Method="HEAD")]
public Stream Download(string token) { }
// A method can not have multiple WebInvoke attributes
[OperationContract]
[WebInvoke(Method="GET")]
[WebInvoke("HEAD")]
public Stream Download(string token) { }
The trick is to use * as Method and handle the method related logic in your code:
[OperationContract]
[WebInvoke(Method="*")]
public Stream Download(string token)
{
var method = WebOperationContext.Current.IncomingRequest.Method;
if (method == "HEAD") return ProcessHead();
if (method == "GET") return ProcessGet();
throw new ArgumentException(method + " is not supported.");
}