shared contacts api for users

[foram]

Hello everyone,

I am passing admin username and password from my code through sesssion but I want that any user from the domain can update shared contacts.Is it possible If not then which is better way to update shared contacts using .net c#.

I am using below code,

        RequestSettings rs = new RequestSettings("test", Session["adminusername"].ToString(), Session["adminpass"].ToString());

        rs.AutoPaging = true;

        ContactsRequest cr = new ContactsRequest(rs);

        Uri uri = new Uri("https://www.google.com/m8/feeds/contacts/mydomain/full");

        ContactsQuery query = new ContactsQuery(uri.ToString());

        Feed<Contact> f = cr.Get<Contact>(query);

I want any user from the organization can update the external contacts but i am passing any user here it gives me error.

Please let me know if it is not possible by user and only administrator can update it which is the better way to authorized it and update external contacts?

Please help

Thanks

Foram