If you want to make them reusable across the site collection for each
user you can add Fields to the User Information List. You can add a
feature receiver to your web parts solution that can create this
column or check to see if this column exists in the User information
list to be sure that the Column exists.
The User Information list is a Standard SharePoint list that
SharePoint uses to store user information. To access the User
Information List you can go to the Root web of the Site Collection and
use the SiteUserInfoList property
E.G.
SPList userInformationlist = SPContext.Current.Site.RootWeb.SiteUserInfoList;
//Or
SPWeb web = SPContext.Current.Site.RootWeb;
SPList userInformationlist = web.SiteUserInfoList;
To access a users List Item you can use the Users Id to get the
ListItem back from the User Information List
E.G.
SPListItem currentUserItem = userInformationlist.GetItemById(web.CurrentUser.ID);
If you are using MOSS you can store this information in the User
Profiles and make it available across Site Collections this does not
need My Sites to be enabled. You would need to use the User Profile
classes to access this.
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