retrieving a data of a specific user

Hi Sonia,

I'm assuming you have added custom fields for users following this manual from the documentation. In this case you should be able to query or filter by these fields like this using Query API:

var users = UserInfoProvider.GetUsers()
    .WhereEquals("CustomField1", "something")
    .Or()
    .WhereStartsWith("CustomField2", "something else")
    .ToList();