probelm regarding download code in c# language

hello sir i am vikas choudhary i have faced a probelm in my web application ,my probelm is :i want to download a file using c# code and code is working properly when website runs on local system,but now when i deployed website and then download a file then downloading is start but after some time i got a error   :file can't be download bcoz source file could not be read...