Tip of the day: Invisible WebFileUploader with select file button
So here is the code for the shown event of the file uploader:
// connect + from FileUploader1 to Button1
js = "document.getElementById('"+FileUploader1.ControlID+_
"_form').appendChild(document.getElementById('"+Button1.ControlID+"'));"+_
"var chooser=document.getElementById('"+FileUploader1.ControlID+_
"_form').getElementsByClassName('chooser')[0];" +_
"var input = chooser.getElementsByTagName('input')[0];"+_
"chooser.style.cssText = 'position: absolute; left: 0px; bottom: 0px; width: "+str(button1.Width)+_
"px; height: "+str(button1.Height)+"px; overflow: hidden;';"+_
"input.style.cssText = 'position: absolute; left: 0px; bottom: 0px; background-color: #FFFFFF;opacity: 0;filter: alpha(opacity=0);width: 100%;height: 100%;';"+_
"document.getElementById('"+Button1.ControlID+"').appendChild(input);"
ExecuteJavaScript js
As you see it's not that difficult. We find the button and the input item from the uploader. Than we assign some css to keep the styles working and add the input area as a child to the button.
Example project: InvisibleFileUploaderWithButton.zip