问AD LDS错误“服务器上没有这样的对象”

EN

 Var host = "Hostname";// soemthing like SV1DCVDEVDB789 where AD LDS is instaed
 var port = 389;//Port Number
 var machineName = string.Format("{0}:{1}", host, port);
 var container = "CN=PSExtUser,CN=PSADLDSPartition1,DC=PS,DC=COM";
 var principalContext = new    PrincipalContext(ContextType.ApplicationDirectory, machineName, container);

//Check id user already exist

UserPrincipal usr = UserPrincipal.FindByIdentity(principalContext, userId);


//if usr is null create new user as below code

      UserPrincipal newUser = new UserPrincipal(principalContext);
                newUser.Name = userId;
                newUser.UserPrincipalName = userId;
                newUser.SetPassword(pwd.ToString());
                newUser.Enabled = false;
                newUser.Save();



////REsponse obtained 





[DirectoryServicesCOMException (0x80072030): There is no such object on the server.
]
   System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail) +597561
   System.DirectoryServices.DirectoryEntry.Bind() +44
   System.DirectoryServices.DirectoryEntry.get_AdsObject() +42
   System.DirectoryServices.DirectoryEntry.get_Options() +42
   System.DirectoryServices.AccountManagement.PrincipalContext.DoLDAPDirectoryInit() +351

[PrincipalOperationException: There is no such object on the server.
]
   System.DirectoryServices.AccountManagement.PrincipalContext.DoLDAPDirectoryInit() +495548
   System.DirectoryServices.AccountManagement.PrincipalContext.DoApplicationDirectoryInit() +61
   System.DirectoryServices.AccountManagement.PrincipalContext.Initialize() +184
   System.DirectoryServices.AccountManagement.PrincipalContext.get_QueryCtx() +42