An IMultipartStreamProvider suited for use with HTML file uploads for writing file content to a FileStream. The stream provider looks at the <b>Content-Disposition</b> header field and determines an output Stream based on the presence of a <b>filename</b> parameter. If a <b>filename</b> parameter is present in the <b>Content-Disposition</b> header field then the body part is written to a FileStream, otherwise it is written to a MemoryStream. This makes it convenient to process MIME Multipart HTML Form data which is a combination of form data and file content.