Question

I’m getting the above exception and error on the following code, which is meant to play a selected mp3 file from Isolated Storage:

using (var isf = IsolatedStorageFile.GetUserStoreForApplication())
{            
     using (var isfs = isf.OpenFile(selected.Path, FileMode.Open))
     {                        
          this.media.SetSource(isfs);              
          isfs.Close();                        
     }                    
     isf.Dispose();
}

The error is so vague that I’m not really sure what could be wrong… Any ideas or at least common sources of this error that I could potentially check for?

EDIT: the exception is being thrown at: using(var isfs = isf.OpenFile(...))

EDIT 2: The stack trace…

at System.IO.IsolatedStorage.IsolatedStorageFileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, IsolatedStorageFile isf)
at System.IO.IsolatedStorage.IsolatedStorageFileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, IsolatedStorageFile isf)
at System.IO.IsolatedStorage.IsolatedStorageFileStream..ctor(String path, FileMode mode, IsolatedStorageFile isf)
at Ringify.Phone.PivotContent.RingtoneCollectionPage.MediaIconSelected(Object sender, GestureEventArgs e)
at MS.Internal.CoreInvokeHandler.InvokeEventHandler(Int32 typeIndex, Delegate handlerDelegate, Object sender, Object args)
at MS.Internal.JoltHelper.FireEvent(IntPtr unmanagedObj, IntPtr unmanagedObjArgs, Int32 argsTypeIndex, Int32 actualArgsTypeIndex, String eventName)

I’ve realized too that the error does NOT occur if I play one song then stop it (there is a play and pause button in the UI), then play another song. It occurs when I play one song, stop it, and attempt to play the same song again.

Answer 1

The problem occurs when you play the same music twice, therefore it may be a file sharing problem. You should try to provide the FileShare parameter of the OpenFile method:

var isfs = isf.OpenFile(selected.Path, FileMode.Open, FileShare.Read)

Though I don’t understand why it would happen, since you’re explicitly closing the file.

EDIT: OK, did some digging with Reflector, and I figured it out. The code of MediaElement.SetSource is:

public void SetSource(Stream stream)
{
    if (stream == null)
    {
        throw new ArgumentNullException("stream");
    }
    if (stream.GetType() != typeof(IsolatedStorageFileStream))
    {
        throw new NotSupportedException("Stream must be of type IsolatedStorageFileStream");
    }
    IsolatedStorageFileStream stream2 = stream as IsolatedStorageFileStream;
    stream2.Flush();
    stream2.Close();
    this.Source = new Uri(stream2.Name, UriKind.Absolute);
}

So basically it doesn’t use the stream you give, and it even closes it. But it keeps the name of the file, and I guess it re-opens it when you play the music. Therefore, if you try to re-open the same file with exclusive access while the music is playing, it fails because the MediaElement has the file opened. Tricky.