Multiple asynchronous file upload asp.net -

i using ajax asynchronous file upload control in asp.net. in application there 2 such upload controls. when uploading 1 file @ time, both files getting uploaded. when uploading 2 files simultaneously , first file getting uploaded. can please tell me, root cause , solution this?.

thanks in advance.

i got solutions this. have added different update panel each file upload control , set updatemode conditional. fixed problem.