//GetUsers 

DirectorySearcher searcher = new DirectorySearcher(de);

searcher.Filter = "(objectClass=user)";  

searcher.SearchScope = SearchScope.Subtree; 

SearchResultCollection results = searcher.FindAll(); 

UserCollection users = new UserCollection(); 

users.Users = new User[results.Count]; 

int index = 0; 

    foreach (SearchResult result in results) 

    { 

        DirectoryEntry directoryEntry = result.GetDirectoryEntry(); 

        users.Users[index] = new User();  

        users.Users[index].Email = (directoryEntry.Properties["Mail"].Count >= 1) ? directoryEntry.Properties["Mail"][0].ToString() : ""; 

        string DomainName = ""; 

        string distinguishedName = (directoryEntry.Properties["distinguishedName"].Count >= 1) ? directoryEntry.Properties["distinguishedName"][0].ToString() : ""; 

        string[] TempStr = distinguishedName.Split(','); 

        foreach (string Str in TempStr) 

        { 

            if (Str.Contains("DC=")) 

            { 

                DomainName = Str.Replace("DC=", ""); 

                break; 

            } 

        } 

        string UserName = (directoryEntry.Properties["sAMAccountName"].Count >= 1) ? directoryEntry.Properties["sAMAccountName"][0].ToString() : ""; 

        users.Users[index].UserName = (DomainName != "") ? DomainName + "\\" + UserName : UserName;  

        users.Users[index].FirstName = (directoryEntry.Properties["givenName"].Count >= 1) ? directoryEntry.Properties["givenName"][0].ToString() : ""; 

        users.Users[index].LastName = (directoryEntry.Properties["Sn"].Count >= 1) ? directoryEntry.Properties["Sn"][0].ToString() : ""; 

        users.Users[index].DisplayName = (directoryEntry.Properties["displayName"].Count >= 1) ? directoryEntry.Properties["displayName"][0].ToString() : ""; 

        users.Users[index].Description = (directoryEntry.Properties["description"].Count >= 1) ? directoryEntry.Properties["description"][0].ToString() : ""; 

        index++; 

 }