"Microsoft.Usage", "CA2202:Do not dispose objects multiple times"

DoNotDisposeMultipleTimes.cs

            using (var stream = new MemoryStream())
            using (var writer = new StreamWriter(stream) { AutoFlush = true })
            {
                writer.Write(message.Xml);

                stream.Seek(0, SeekOrigin.Begin);

                this.documentSession.StoreAttachement(
                    "someId", null, stream, new RavenJObject { { "Content-Type", "application/xml" }, });
            }

If I had to guess, I'd say stream is being disposed within writer first when writer is disposed, and then again after stream's using statement ends, so just create the stream without a using statement.

using (var writer = new StreamWriter(new MemoryStream()) { AutoFlush = true })
{
    writer.Write(message.Xml);

    stream.Seek(0, SeekOrigin.Begin);

    this.documentSession.StoreAttachement(
        "someId", null, stream, new RavenJObject { { "Content-Type", "application/xml" }, });
 }

It's equal to the official MSDN documentation: http://msdn.microsoft.com/it-it/library/ms182334.aspx