Collections and ICollection.Syn cRoot

[Gavin]

I am using collections in my project and have come up against some
issues. My project is a web based thin client application.

The main issue I have is with collections, I have all the users
settings/permissions etc held in a collection which is in a module.

This enables the user to access their settings from page to page
without quering a database every time the page loads.

Administrators of the system can change users settings while the user
is logged in. But, after reading up on collections that have multiple
readers/writers I discovered that I need to lock the collection before
the administrator can apply the changes, as there could be more than
one admin changing a setting.

I have read through MS documentation and have put together the code
below, which seems to be working, but I have no way of really knowing,
as the only test I can do is try editing the sam account at the same
time from various computers, which does seem to work.

Please can someone verify I have done this correctly?

Here is the UserGroupPermis sionCollection:

Public Class UserGroupPermis sionCollection
Inherits System.Collecti ons.CollectionB ase

Private _userGroupIdHas htable As New Hashtable

Public ReadOnly Property UserGroupIdHash table() As Hashtable
Get
Return _userGroupIdHas htable
End Get
End Property

Public Sub Add(ByVal newUserGroupFun ctions As
UserGroupFuncti onCollection)
Me.List.Add(new UserGroupFuncti ons)
UserGroupIdHash table.Add(newUs erGroupFunction s.Id,
newUserGroupFun ctions)
End Sub

Public Sub Remove(ByVal removeUserGroup Functions As
UserGroupFuncti onCollection)
Me.List.Remove( removeUserGroup Functions)
UserGroupIdHash table.Remove(re moveUserGroupFu nctions.Id)
End Sub

Default Public ReadOnly Property Item(ByVal userGroupId As Int32)
As UserGroupFuncti onCollection
Get
Return UserGroupIdHash table.Item(user GroupId)
End Get
End Property

Public Shadows Sub Clear()
MyBase.Clear()
UserGroupIdHash table.Clear()
End Sub

End Class

This is the declaration and property in the module:

Private _userGroupPermi ssions As New UserGroupPermis sionCollection

Public ReadOnly Property UserGroupPermis sions() As
UserGroupPermis sionCollection
Get
Return _userGroupPermi ssions
End Get
End Property
This is my code in the aspx page:

Dim _newUserGroupFu nctions As New UserGroupFuncti onCollection
Dim userGroupFuncti on As UserGroupFuncti on

....Do some stuff and set values in the userGroupFuncti on Structure and
Add them to the _newUserGroupFu nctions Collection

Dim _userGroupPermi ssions As System.Collecti ons.ICollection =
UserGroupPermis sions

SyncLock _userGroupPermi ssions.SyncRoot
'Get current function collection to be removed
Dim _removeUserGrou pFunctions As UserGroupFuncti onCollection = _
UserGroupPermis sions(iUserGrou pId)

If Not _removeUserGrou pFunctions Is Nothing Then
'Remove collection
UserGroupPermis sions.Remove(_r emoveUserGroupF unctions)
End If

UserGroupPermis sions.Add(_newU serGroupFunctio ns) 'Add new
collection
End SyncLock

Is this right or have I totaly missunderstood the whole concepted?