Upload file via image button

Hi
I have this scenario

I have an ImageButton that shows no image, I want when a user click on this imagebutton to get a select file dialog and once he select an image to upload this image to the server and use it as an image for the ImageButton

Mainly I want to know how to open the select dialog from a button and how to upload the file

I do not want to use asp:FileUpload

thanks for your help