Rohan,

 

That is a client side behavior and must be controlled by JavaScript.

 

use startupload() function to start upload the selected files.

 

var uploadobj=document.getElementById('<%=Uploader1.ClientID %>');
uploadobj.startupload();

 

Please check the html code of http://ajaxuploader.com/Demo/Start-uploading-manually.aspx

 

See function submitbutton_click() and function CuteWebUI_AjaxUploader_OnPostback() 

 

Regards,
Terry