string ldapDomain = "LDAP://" + defaultDomainNamingContext;
 try
 {

     step = "DirectorySearcher; ";
     DirectorySearcher ds = new DirectorySearcher(ldapDomain);
     try
     {
         ds.PropertiesToLoad.Add("SamAccountName");
         ds.PropertiesToLoad.Add("userPrincipalName");   //  17-01-2022
         ds.PropertiesToLoad.Add("mail");                //  17-01-2022
         ds.Filter = "(&(SamAccountName=" + userName + "))";
         step += $"filter={ds.Filter}. ds.FindOne().";
         userProperty = ds.FindOne();
     }
     finally
     {
         ds.Dispose();
     }
     step += "ds.FindOne end; ";

                entry = new DirectoryEntry(ldapDomain);  // 20-01-2022. Раньше не было
                logs_info = $"entry.Path={entry.Path}";
                step = "DirectorySearcher; ";
                // 20-01-2022 DirectorySearcher ds = new DirectorySearcher(ldapDomain);
                DirectorySearcher ds = new DirectorySearcher(entry);
                try
                {
                    ds.PropertiesToLoad.Add("SamAccountName");      //  17-01-2022
                    ds.PropertiesToLoad.Add("userPrincipalName");   //  17-01-2022
                    ds.PropertiesToLoad.Add("mail");                //  17-01-2022
                    ds.Filter = "(&(SamAccountName=" + userName + "))";
                    step += $"filter={ds.Filter}. ds.FindOne()";
                    userProperty = ds.FindOne();
                }
                finally
                {
                    ds.Dispose();
                    entry.Close();
                }