How to query Active Directory given multiple user names?

Question

I use System.DirectoryServices.AccountManagement to query Active Directory for a single user info

public UserInfo FindOne(string samUserName)
{
    using (var ctx = new PrincipalContext(ContextType.Domain, "domain.com", "Bob", "pwd"))
    {
        using (UserPrincipal user = UserPrincipal.FindByIdentity(ctx, samUserName))
        {
            if (user != null)
            {
                // get info about Alice into userInfo
                return userInfo;
            }
        }   
    }

    return null;
}

So if I use var aliceInfo = search.FindOne("alice"); I get info from the directory. Now I need to search a directory (1000+ users) given several user logon names, for example

var userInfos = search.FindMany(/* list of names: alice, jay, harry*/);

How to implement the following method?

public List<UserInfo> FindMany(List<string> samUserNames)
{
    ...
}

Answer 1

Try this:

string query = "dc=com,dc=domainController,ou=Users"; //this is just an example query, change it to suit your needs

// create your domain context and define the OU container to search in
PrincipalContext ctx = new PrincipalContext(ContextType.Domain, "yourDomain", query);

// define a "query-by-example" principal - here, we search for a UserPrincipal (user)
UserPrincipal qbeUser = new UserPrincipal(ctx);

// create your principal searcher passing in the QBE principal    
PrincipalSearcher srch = new PrincipalSearcher(qbeUser);

return srch.FindAll().Select(p => p as UserPrincipal);

This way you can return all users from AD, and then filter out those you don't need. UserPrincipal has a few user related attributes, like Surname and Sid, but if you need to get a value that UserPrincipal doesn't have, you can create an extension method and access any LDAP attribute:

    public static String GetProperty(this Principal principal, String property)
    {
        DirectoryEntry directoryEntry = principal.GetUnderlyingObject() as DirectoryEntry;
        if (directoryEntry.Properties.Contains(property))
            return directoryEntry.Properties[property].Value.ToString() ?? "";
        else
            return String.Empty;
    }

Here is a list of LDAP attributes: https://fsuid.fsu.edu/admin/lib/WinADLDAPAttributes.html