So What i am looking for is like below sample code
var Radfile_uploader = document.getElementById(file_uploader_name);
var file_content = new Array();
for (i=0;i<=file_uploader.files.count -1;i++)
var file_content = file_uploader.files[i].getAsBinary();
than i can pass this file_content to my WCF service as string.