Here Mudassar Ahmed Khan has explained how to upload multiple files with ASP.Net 4.5 FileUpload control in Visual Studio 2012 and Visual Studio 2013.
With the invention of HTML5, the FileUpload control now supports selection of multiple files at once and all the selected files are uploaded together. For uploading multiple files from a FileUpload control you just need to set the AllowMultiple property to true.
The only catch is that this feature is only available in browsers supporting HTML5 i.e. Internet Explorer (IE10) or higher, Firefox and Chrome.