Use the RenderedOutputFile class for a delivery extension
The RenderedOutputFile class represents a data stream and information about the data stream's associated properties. The Data property of the RenderedOutputFile class is used to represent a rendered report or report resource as a Stream object.
The Render method of the Report object returns an array of one or more RenderedOutputFile objects that together constitute a single rendered report. The first RenderedOutputFile object is the rendered report. Any other RenderedOutputFile objects are resources that must be delivered along with the report data (for example, an HTML file and associated images). Rendering extensions that are single-stream rendering extensions (IMAGE, PDF, MHTML, and EXCEL) return only one RenderedOutputFile object in the array.
For an example of how to use the RenderedOutputFile class, see SQL Server Reporting Services Product Samples.