Update Manager Name in Active Directory Using C#

Public Shared Function GetDirectoryEntry() As DirectoryEntry
            Dim dirEntry As DirectoryEntry = New DirectoryEntry()
            dirEntry.Path = "LDAP://DC=??????,DC=???"
            dirEntry.Username = ???????
            dirEntry.Password = ???????
            Return dirEntry
End Function
Public Shared Function UpdateManager(ByVal UserAccount As String, ByVal ManagerAccount As String)
            Dim EmployeeSAM As String = UserAccount

            'you have to use the current user account or any domain admin user account
            Dim objDirEnt As DirectoryEntry = GetDirectoryEntry()

            'searcher object to select the current user from the Active directory
            Dim mySearcher As DirectorySearcher = New DirectorySearcher(objDirEnt)

            mySearcher.PageSize = 10000
            'you can increase it according to your active directory database size

            mySearcher.Filter = "(&(objectCategory=user)(samAccountName=" + EmployeeSAM + "))"
            'you can add any filter you want 
            mySearcher.PropertiesToLoad.Add("samAccountName")
            mySearcher.PropertiesToLoad.Add("Manager")
            mySearcher.SearchScope = SearchScope.Subtree
            Dim result As SearchResult
            Dim resultCol As SearchResultCollection = mySearcher.FindAll()
            'you can use the colliction for bulk update
            If resultCol.Count <> 0 Then
                For counter As Integer = 0 To resultCol.Count Step 2
                    result = resultCol(counter)
                    Dim Userde As DirectoryEntry = result.GetDirectoryEntry()
                    'the directory entry for the user 
                    If (result.Properties.Contains("samaccountname")) Then
                        'check if it is a valid entry
                        Dim ManagerSAM As String = ManagerAccount 'manager Account 
                        Dim managerSearcher As DirectorySearcher = New DirectorySearcher(objDirEnt)
                        managerSearcher.PageSize = 10
                        managerSearcher.Filter = "(&(objectCategory=user)(samAccountName=" & ManagerSAM & "))"
                        managerSearcher.PropertiesToLoad.Add("DistinguishedName")
                        managerSearcher.SearchScope = SearchScope.Subtree
                        Dim managerResult As SearchResult
                        Dim managerResultCol As SearchResultCollection = managerSearcher.FindAll()
                        If managerResultCol.Count <> 0 Then
                            managerResult = managerResultCol(0)
                            Dim managerName As String = managerResult.Properties("DistinguishedName")(0)
                            'here update the manager name 
                            'in the user directtory entry "Userde"
                            Userde.Properties("Manager").Value = managerName
                            Userde.CommitChanges()
                        End If
                    End If
                Next
            End If
        End Function