Thank you very much Ryan, you are right i made a mistake in username definition.i did update successfully. now i want to insert a user, i wrote it like: DirectoryEntry de= new DirectoryEntry(ldapPath); de.AuthenticationType =AuthenticationTypes.None; de.Username = "uid=Admin,ou=AdmUsers,dc=domain";; de.Password = "Password"; DirectoryEntry child=de.Children.Add("uid=myname","People"); child.Properties["p1"].Value = "p1"; child.Properties["p2"].Value = "p2"; child.CommitChanges() ; i take the message "The requested operation did not satisfy one or more constraints associated with the class of the object." i dont know where am i wrong?do i have to fill all of the properties define in LDAP setup? in visual basic i used opendsobject for update but in MSDN i found a code to insert by using "samaacountname". since i did not use AD i dont know what to use to insert in VB? thank you.