When you don't have a file on disk, you can either

<ul>
	<li>
		<p>
			Use one of the built-in file providers to load a document from a URL, Database, Stream, Memory, AzureBlob, AmazonS3 etc. :
			FileSystemFileProvider, UrlFileProvider, StreamFileProvider,
			MemoryFileProvider, DatabaseFileProvider,
			AssemblyResourceFileProvider, TemporaryFileProvider.
		</p>
	</li>
    <li>
	    <p>
		    Or implement base class FileProvider to provide a custom way of reading and/or writing files (see CustomFileProvider class in example code for details).
	    </p>
    </li>
</ul>