Get SPUsers From SharePoint PeoplePicker Control

Code below shows how to retrieve SPUsers from the SharePoint PeoplePicker control when PeoplePicker control is set to only allow users (SelectionSet="User"):

<SharePoint:PeopleEditor id="peoplePicker" runat="server" AllowEmpty="true" ValidatorEnabled="true" MultiSelect="true" SelectionSet="Group"/>

public static List<SPUser> GetPeopleEditorUsers(PeopleEditor picker)
{
    List<SPUser> users = new List<SPUser>();
    try
    {
        foreach (PickerEntity entity in picker.ResolvedEntities)
        {
            if ((string)entity.EntityData["PrincipalType"] == "User")
            {
                int userID = Int32.Parse(entity.EntityData["SPUserID"].ToString());
                SPUser user = SPContext.Current.Web.SiteUsers.GetByID(userID);
                if (user != null)
                {
                    users.Add(user);
                }
            }
        }
    }
    catch (Exception ex)
    {
        //Log error
    }
    return users;
}

The code needs to be revised a bit when groups are included in the PeoplePicker (SelectionSet="SPGroup,DL,SecGroup"):

public static List<SPUser> GetPeopleEditorGroupUsers(PeopleEditor picker)
{
    List<SPUser> users = new List<SPUser>(); 
    try
    {
        foreach (PickerEntity entity in picker.ResolvedEntities)
        {
            if ((string)entity.EntityData["PrincipalType"] == "SharePointGroup")
            {
                int groupID = int.Parse((string)entity.EntityData["SPGroupID"]);
                SPGroup group = SPContext.Current.Web.SiteGroups.GetByID(groupID);
                foreach (SPUser user in group.Users)
                {
                    users.Add(user);
                }
            }
        }
    }
    catch (Exception ex)
    {
        //Log error
    }
    return users;
}

The difference between SPWeb.Groups and SPWeb.SiteGroups:

• SPWeb.Groups: Groups explicitly assigned persmissions in a site collection.
• SPWeb.SiteGroups: All valid groups available in the site collection (superset of SPWeb.Groups). You can add a new group to SPWeb.SiteGroups, but not the SPWeb.Groups.

The difference between SPWeb.AllUsers, SPWeb.SiteUsers and SPWeb.Users:

• SPWeb.Users: Users explicitly assigned permissions in a site collection.
• SPWeb.SiteUsers: All valid users available in a site collection (superset of SPWeb.Users).
• SPWeb.AllUsers: All users who are either members of the site or who have browsed to the site as authenticated members of a domain group in the site (superset of SPWeb.SiteUsers).