在后台线程中上传大容量图像

I want to know that how can we upload many number of images using webservice in iPhone with background thread or process. I am storing bulk of images in my iPhone app and i want to upload(post) those images using .net web-service. Right now, i am positing single image using web service but i want to post multiple images in background process. Please help me i will appreciate for it.I want to know that how can we upload many numb