HttpResponse.WriteFile Method (String)
Writes the contents of the specified file directly to an HTTP response output stream as a file block.
Assembly: System.Web (in System.Web.dll)
When this method is used with large files, calling the method might throw an exception. The size of the file that can be used with this method depends on the hardware configuration of the Web server. For more information, see article 812406, "PRB: Response.WriteFile Cannot Download a Large File" on the Microsoft Knowledge Base Web site.