Find username from Active Directory using email id

Question

I am finding user name from Active Directory by passing email id. It is working fine. But it takes 30-40 seconds to get the username. Is there any other better way to find the username from Active Directory by email address?

Please refer to my code:

using (PrincipalContext context = new PrincipalContext(ContextType.Domain, "domainname"))
{
    UserPrincipal userPrincipal = new UserPrincipal(context);
    PrincipalSearcher principalSearch = new PrincipalSearcher(userPrincipal);

    foreach (UserPrincipal result in principalSearch.FindAll())
    {
        if (result != null && result.EmailAddress != null && result.EmailAddress.Equals(user.Email, StringComparison.OrdinalIgnoreCase))
        {
            user.FirstName = result.GivenName;
            user.LastName = result.Surname;
        }
    }
}

Answer 1

You don't need to enumerate all users to to find one of them! Try this code:

using (PrincipalContext context = new PrincipalContext(ContextType.Domain, "domainname"))
{
    UserPrincipal yourUser = UserPrincipal.FindByIdentity(context, EmailAddress);

    if (yourUser != null)
    {
        user.FirstName = yourUser.GivenName;
        user.LastName = yourUser.Surname;
    }
}

If that shouldn't work, or if you need to search for several criteria at once, used the PrincipalSearcher with the QBE (query-by-example) approach - search the one user you need - don't cycle through all users!

// create your domain context
using (PrincipalContext context = new PrincipalContext(ContextType.Domain, "domainname"))
{    
   // define a "query-by-example" principal - 
   UserPrincipal qbeUser = new UserPrincipal(ctx);
   qbeUser.EmailAddress = yourEmailAddress;

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

   // find all matches
   foreach(var found in srch.FindAll())
   {
       // do whatever here - "found" is of type "Principal" - it could be user, group, computer.....          
   }
}