Sharing datasources among forms - VS2005

[Steve Marshall]

I have come across the situation several times where a number of forms
in an app use the same datasource, for example to populate a combo
drop-down. I'm sure we've all had this. Using the IDE results in
every form getting its own Dataset, BindingSource and TableAdapter,
plus code in the Open event to fill the table in the dataset. This
strikes me as incredibly inefficient - there is simply no need for
every form to go to the database to read this data in again. What I
want is a way to set up and populate a dataset once, then just refer
to it in all the forms that might need it. Is there a way to do this
that fits in with the IDE? If there is it isn't obvious to me.

[Cor Ligthert [MVP]]

Steve,

It is strange, because the version 2003 has this behaviour. The version 2005
creates it on its own datasource where the tableadapter can be build in. It
is a class on its own including data and connection to the database.

Can you tell us how you build up your tableadapter?

Cor

"Steve Marshall" <st****@westnet .net.auschreef in bericht
news:11******** *************@p 10g2000cwp.goog legroups.com...

>I have come across the situation several times where a number of forms
in an app use the same datasource, for example to populate a combo
drop-down. I'm sure we've all had this. Using the IDE results in
every form getting its own Dataset, BindingSource and TableAdapter,
plus code in the Open event to fill the table in the dataset. This
strikes me as incredibly inefficient - there is simply no need for
every form to go to the database to read this data in again. What I
want is a way to set up and populate a dataset once, then just refer
to it in all the forms that might need it. Is there a way to do this
that fits in with the IDE? If there is it isn't obvious to me.

[RobinS]

If you were really concerned about the performance, you could create a
public class with shared properties that point to datatables that you're
using to bind to comboboxes all over your app, and access that everywhere.

Robin S.
-------------------------
"Steve Marshall" <st****@westnet .net.auwrote in message
news:11******** *************@p 10g2000cwp.goog legroups.com...

>I have come across the situation several times where a number of forms
in an app use the same datasource, for example to populate a combo
drop-down. I'm sure we've all had this. Using the IDE results in
every form getting its own Dataset, BindingSource and TableAdapter,
plus code in the Open event to fill the table in the dataset. This
strikes me as incredibly inefficient - there is simply no need for
every form to go to the database to read this data in again. What I
want is a way to set up and populate a dataset once, then just refer
to it in all the forms that might need it. Is there a way to do this
that fits in with the IDE? If there is it isn't obvious to me.

[Steve Marshall]

Yes, an approach like that has occurred to me, and I will pursue it.
It just doesn't seem to fit as naturally as I would like with the way
the IDE does things. Thanks for the reply.
On Feb 26, 9:38 am, "RobinS" <Rob...@NoSpam. yah.nonewrote:

If you were really concerned about the performance, you could create a
public class with shared properties that point to datatables that you're
using to bind to comboboxes all over your app, and access that everywhere.

Robin S.
-------------------------"Steve Marshall" <ste...@westnet .net.auwrote in message

news:11******** *************@p 10g2000cwp.goog legroups.com...

I have come across the situation several times where a number of forms
in an app use the same datasource, for example to populate a combo
drop-down. I'm sure we've all had this. Using the IDE results in
every form getting its own Dataset, BindingSource and TableAdapter,
plus code in the Open event to fill the table in the dataset. This
strikes me as incredibly inefficient - there is simply no need for
every form to go to the database to read this data in again. What I
want is a way to set up and populate a dataset once, then just refer
to it in all the forms that might need it. Is there a way to do this
that fits in with the IDE? If there is it isn't obvious to me.- Hide quoted text -

- Show quoted text -

[Bart Mermuys]

Hi,

"Steve Marshall" <st****@westnet .net.auwrote in message
news:11******** *************@z 35g2000cwz.goog legroups.com...

Yes, an approach like that has occurred to me, and I will pursue it.
It just doesn't seem to fit as naturally as I would like with the way
the IDE does things. Thanks for the reply.

<text snipped>

Here is some addition info:

After compiling the class (example) below, you can create an object Data
Source from it (Data Source's window, add new Data Source). Once you have
the Data Source you can use it with the WinForm designer and the DataTable
will only be loaded once when it's first used.

Imports WindowsApplicat ion1.SomeDBData SetTableAdapter s

Public Class GlobalCompanyDa taSource
Implements System.Componen tModel.IListSou rce

Public Shared _Table As SomeDBDataSet.C ompanyDataTable

Public Shared ReadOnly Property Table() As
SomeDBDataSet.C ompanyDataTable
Get
If (_Table Is Nothing) Then
_Table = New SomeDBDataSet.C ompanyDataTable
Dim cta As New CompanyTableAda pter
cta.Fill(_Table )
cta.Dispose()
End If
Return _Table
End Get
End Property

Public ReadOnly Property ContainsListCol lection() As Boolean Implements
System.Componen tModel.IListSou rce.ContainsLis tCollection
Get
Return False
End Get
End Property

Public Function GetList() As System.Collecti ons.IList Implements
System.Componen tModel.IListSou rce.GetList
Return Table.DefaultVi ew
End Function
End Class

If your form needs to contain global and a non global DataTable's which are
part of the same DataSet, then you could just use the DataSet on the Form
and then replace the fill line in Form_Load for the global DataTable, this
way you can still enforce referential integrity (fk constraints).

Private Sub Form_Load(...)
' fill lookup (global)
SomeDBDataSet.C ompany.Merge(Co mpanyGlobalSour ce.Table)

' fill master (non-global)
EmployeeTableAd apter.Fill(Some DBDataSet.Emplo yee)
End Sub
HTH,
Greetings