Straight to your questions.
RadUpload control is using a standard input type="file"
control. With it, it is possible go get the picture full path and set it to image source. Unfortunately it is possible to do this only in IE.
With RadUpload control you need to submit the page in order to upload files. UploadedFiles
property of RadUpload gives you access to the uploaded files. You can save and point them as an image source.
My suggestion is to use the RadAsyncUpload control. For more information, please consult with the following demo
All the best,
the Telerik team