session variable in dotnet web application

Question

hi,

 

i have one website which takes user data .each user has its login id, i am using session variable for each user .problem coming with me is if one user login and upload  his photograph and sign and other details and after that other other user from same computer login his credentials and upload his photo and sign and other details authomatically detail of first users is overwrite with second user like photo of first user is repliace with second user and same with sign and other things ,i dont know what is happening i try debugging code n my local computerits is working well .please suggest what is wrong going on