Login portal and client file sharing

Hi, I have a website and I want to have a client login page and when they login they are brought to a page or subsite where they can upload files and where we can share files between the client and our company. We have a few clients and for each one I would only want them to see files that apply to them. Does anyone have any ideas for how this could be accomplished and what technologies it might involve? Thanks!

Use Forms Authentication and control access of specific folders through web.config.

Check these articles -
Forms Authentication for ASP.NET Application Subdirectories
Role-based Security with Forms Authentication

I would only want them to see files that apply to them

i think you can create respective directories for each users and then use form authentication.

Another way that you can follow is that :

create a table describe which file can be viewed by which user ;

create a girdview/list view which will list all the files the user can access, and bind the gridview/list view to that talbe;

when user went to that page, run a sql- query which will return all the files the user can access;

Hope my suggestion helps :)