How to display image preview without saving in database or folder in ASP.Net

i used a file upload control to upload file..after uploading i want to preview image without storing its path or storing in DB or solution explorrer folder.

when i upload using fileupload control..path of image comes in fileupload control

now i used a button so,that on button click image should be displayed in image control..

how it can be done..

plz help

Thanks