Search for user in other Active Directory domain

I created one ParentDomain ADDomain1 having a child ADDomain2. In ADDomain2 I created a Group 'Common Users' in this I have users both from ADDomain1 as well ADDomain2, but when I do a directory search for a ADDomain1 user in ADDomain2 it doesn't retuen any result. here is a code

DirectorySearcher directorySearcher = new Directory开发者_开发知识库Searcher();

 DirectoryEntry directoryEntry = new DirectoryEntry("LDAP://ADDomain2","UserName","Password");
directoryEntry.Path = "LDAP://ADDOMAIN2/DC=ADDOMAIN2,DC=ADDOMAIN1,DC=WAVEDOMAIN";
directorySearcher.SearchRoot = directoryEntry;
            directorySearcher.FindOne();
directorySearcher.PageSize = 1000;
            directorySearcher.Filter = "(&(objectCategory=person)(name=ADDOMAIN1User))";
SearchResultCollection results = directorySearcher.FindAll();

But when I search for ADDOMAIN2 user it returns results.

Any Idea?

Thanx

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I don't know about DirectoryEntry, does it work with UserPrincipal? Is AD2 a global catalog?

Sample:

using System.DirectoryServices.AccountManagement;
var ctx = new PrincipalContext(ContextType.Domain, "ADDOMAIN2");
var usr = UserPrincipal.FindByIdentity(ctx, IdentityType.SamAccountName, "whatever");
// you can also find the GroupPrincipal and get its members