据我所知，你将不得不这样做对用户的LDAP搜索，并从AD获得的的distinguishedName 属性。见下图：

To my knowledge you will have to do an LDAP Search for the user and get the distinguishedName property from AD. See below:

// you can use any root DN here that you want provided your credentials
// have search rights
DirectoryEntry searchEntry = new DirectoryEntry("LDAP://XYZ:389");

DirectorySearcher search = new DirectorySearcher(searchEntry);
search.Filter = "(&(objectclass=user)(objectCategory=person)" +
  "(sAMAccountName=" + userName + "))";    

if (search != null)
{
  search.PropertiesToLoad.Add("sAMAccountName");
  search.PropertiesToLoad.Add("cn");
  search.PropertiesToLoad.Add("distinguishedName");

  log.Info("Searching for attributes");

  // find firest result
  SearchResult searchResult = null;
  using (SearchResultCollection src = search .FindAll())
  {
 if (src.Count > 0)
   searchResult = src[0];
  }

  if (searchResult != null)
  {
    // Get DN here
    string DN = searchResult.Properties["distinguishedName"][0].ToString();
  }