Plan B -- dotnet remoting

Russ
8/13/2003 7:42:42 PM

Hi,

I'm using VB.net 1.1 to build a Web based server and a Windows based client.
Having read through two books and various articles I'm beggining to wonder
if this is simply beyond my mental capacity. Sorry this goes on a bit, but
any help would be greatly appreciated.

I have a 'contact' object which is serializable because it is serialised to
a database.

<Serializable()> Public Class Contact
Private I_Name As String

Public Property Name()
Get
Return I_Name
End Get
Set(ByVal Value)
I_Name = Value
End Set
End Property
End Class

I have also defined an object called AllContacts to hold these objects
called which I have inherited from MarshallbyrefObject. This has one
field, a public arraylist to hold the 'contact' objects.

Public Class AllContacts
Inherits MarshalByRefObject
Public Contacts As ArrayList
End Class

I need both the web site and one or more windows based clients to be able to
add new contacts and edit existing ones to this. For the website, I have
defined everything at application level in a module, so the objects are
available to all aspx pages. For the purposes of this test, Session Start
calls the Initailize sub which adds 2 contacts and then publishes the ACs
object.

Module MainModule
Public ACs As New AllContacts
Public Ref As ObjRef

Sub Initailize()
add2cs()
SetChannel()
End Sub

Sub SetChannel()
Dim Channel As Http.HttpChannel
Channel = New Http.HttpChannel
ChannelServices.RegisterChannel(Channel)
Ref = RemotingServices.Marshal(ACs, "all.rem")
End Sub

Sub add2cs()
Dim C As Contact
C = New Contact
C.Name = "bob"
ACs.Contacts.Add(C)
C = New Contact
C.Name = "john"
ACs.Contacts.Add(C)
End Sub
End Module

Webform1.aspx then displays ACs.Contacts.count which when the site first
starts has a value of 2.

My client code also references the classes defined above looks like this.

Public Class Form1
Inherits System.Windows.Forms.Form
Dim AllCs As AllContacts
Dim Cs As ArrayList

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Connect()
End Sub

Sub Connect()
AllCs = Activator.GetObject(GetType(AllContacts),
"http://work/remserver/all.rem")
Cs = AllCs.Contacts
' At this point Cs.length = 2 - great!
End Sub

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles Button1.Click
Dim C As New Contact
C.Name = "bill"
AllCs.Contacts.Add(C)
Cs = AllCs.Contacts
' Cs.length is still 2 - not great
End Sub
End Class

When I run this, Cs.length = 2 the line after Activator.getobject which is
what I would expect, but clicking Button1 has no effect, I would now have
expected Cs.length to be 3, but it remains at 2, and I was kinda hoping that
when I refreshed Webform1.aspx on the site, the count would also be 3.

I know I'm obviously missing something fairly fundamental here, but I'm
clueless as to what it is.

Help? Please?

Thanks,
Russ

teeces NO[at]SPAM hotmail.com
8/14/2003 9:36:21 AM

I think I would approach this in a different way. You say that your
Contact class is serializable because you want to store it in a
database. Do you mean you will be serializing and storing each object
of this class in a database table? This is not standard practice for
database apps.

Here's a rough sketch-out of what I would do:
Step 1: In the database
- Create a database table, tblContact.
- Give it a varchar column called Name.

Step 2: the server-side code
- Create a Class Library project that includes two public methods:
GetContacts
UpdateContacts

- Your GetContacts method will receive a dataset object ByRef.
It will fill this dataset with the contents of your tblContact
table.
- Your UpdateContacts method will also receive a dataset object
byref,
and will use it to update tblContacts. This will be done via
the
Update method of the DataAdapter.
- configure remoting for this app to make it available via remoting

Step 3: the client-side code
- create either a Windows app or a Web App
- configure remoting in this app to access the above server-side
DLL
via remoting (either HTTP or TCP)
- put a datagrid on your form
- call your GetContacts method to get a dataset filled with
contacts
- bind this dataset to your grid
- allow the user to add, update, delete contacts in the grid
- Give the user a Save button on the form. When they click Save,
call the
UpdateContacts method and pass the updated dataset.

This is a high-level overview of how the DataGrid, DataSet, and
Remoting come together to make a distributed app. You can have a
single server-side component that is accessed from multiple clients,
including Win Form, Web Form, or API-style access (i.e. from another
application). And you don't have to use remoting for this; you can do
basically the same thing using a web service.

Hope this helps.

John

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