I've had great success using SlickUpload on my development and qa sites. However, when I move it up to an Azure hosted environment, the exception below gets thrown after a file is selected and the upload is attempted. Any ideas on what's going on here and how to resolve it? We're storing SessionState in an Azure hosted SQL Server database.

Thanks,
Alan

Exception information:
    Exception type: WebException
    Exception message: The remote server returned an error: (404) Not Found.
   at System.Net.HttpWebRequest.GetResponse()
   at Krystalware.SlickUpload.Web.SessionStorage.SessionStateSessionStorageProvider.Ⴗ(String Ⴓ, Object Ⴐ, HttpCookieCollection Ⴗ)
   at Krystalware.SlickUpload.Web.SessionStorage.SessionStateSessionStorageProvider.Ⴓ(String Ⴓ, Object Ⴐ)
   at Krystalware.SlickUpload.Web.SessionStorage.SessionStateSessionStorageProvider.GetSession(String uploadSessionId)
   at Krystalware.SlickUpload.Web.SessionStorage.AdaptiveSessionStorageProvider.GetSession(String uploadSessionId)
   at Krystalware.SlickUpload.Web.SlickUploadModule.Ⴅ(Object Ⴓ, EventArgs Ⴐ)
   at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

This is part of the SlickUpload SessionStateSessionStorageProvider standard implementation. There is one limitation to session state that most people aren't aware of -- only one request can access session state at a time. All other requests will block until the first request is done. This makes sense because you don't really want requests stepping on eachother's session, but it creates a problem for us in SlickUpload. The upload is a long running request. If it were to grab the session state lock, progress requests couldn't access the session to get the information back.

The way we have solved this is that the upload request doesn't use session state, but instead accesses session state by calling the SlickUpload.axd with parameters that tell it to access the session state. This way, the session state access requests are short lived and don't block anything.

By default, SlickUpload uses a reference to the same URL it was initially called on, but there is a (currently undocumented) way to override that. Add the handlerUrl attribute to the sessionStorageProvider config and point it to SlickUpload.axd. Something like:

    handlerUrl="http://192.168.1.244/SlickUpload.axd"