The point of a HEAD request is to return a Content-Length header, but with an empty body. The WCF transport stack has the annoying ‘feature’ that it ‘corrects’ the Content-Length header based on the stream that is returned. With the aid of Carlos Figueira’s MyLengthOnlyStream i was able to workaround that ‘feature’ (I know, i know, a good old HttpHandler is so much easier to implement!)

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.");
}

Environment.SpecialFolder is a value-type that i always seem to forget about. Let’s try to do something about that by posting about it here

foreach (var name in Enum.GetNames(typeof(Environment.SpecialFolder)))
{
 var specialFolder = (Environment.SpecialFolder)Enum.Parse(typeof(Environment.SpecialFolder), name);
 Console.WriteLine("{0,25} => {1}", name, Environment.GetFolderPath(specialFolder));
}

Sometimes you want to know the absolute path of a file that is persisted with IsolatedStorageFile. Apparently there is an internal property RootDirectory which contains this information:

public static class IsolatedStorageFileExtensions
{
 public static string GetRootDirectory(this IsolatedStorageFile isf)
 {
  var property = isf.GetType().GetProperty("RootDirectory", BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic | BindingFlags.GetProperty);
  return (string)property.GetValue(isf, null);
 }
}

Here is a real world example of using SharpBITS.NET to download a file to IsolatedStorage:

class Program
{
 static void Main()
 {
  var mgr = new BitsManager();
  mgr.OnJobError += mgr_OnJobError;
  mgr.OnJobTransferred += mgr_OnJobTransferred;

  var job = mgr.CreateJob("job@" + DateTime.Now, JobType.Download);
  var src = @"http://localhost/";
  var dst = Path.Combine(GetIsfRoot(), "test.html");
  job.AddFile(src,dst);
  job.Resume();

  Console.WriteLine("running...");
  Console.ReadKey();
 }

 static void mgr_OnJobTransferred(object sender, NotificationEventArgs e)
 {
   e.Job.Complete();
   Console.WriteLine("completed: " + e.Job.DisplayName);
  }

 static void mgr_OnJobError(object sender, ErrorNotificationEventArgs e)
 {
  Console.WriteLine("error: " + e.Error.Description);
 }

 static string GetIsfRoot()
 {
  using (var f = IsolatedStorageFile.GetUserStoreForAssembly())
  {
   return f.GetRootDirectory();
  }
 }
}