I have designed a user control (UserControl0) from which several other user
controls (ChildUserControl(n)) inherit.  Each ChildUserControl(n) has its own
strongly typed dataset.  I would like to include several (overridable)
methods in UserControl(0) that act on the datasets (nothing exotic, only
things that can be executed against an untyped dataset).  Occasionally, I
will want to override these methods and exploit the strong typing.  What is
the best way to go about this?

I think I want to do something like this:

Class UserControl0
  Private mds as Dataset
  Private mMyString as String

  Protected Property DS as Dataset
    Get
      return mds
    End Get
    Set (value as Dataset)
      mds=value
    End Set
  End Property

  Protected Overridable Sub MyExample
    mMyString=mds.Tables(0).TableName
  End Sub
..
..
..
..
End Class

Class ChildUserControl
  Inherits UserControl0

  Private mds as MyStronglyTypedDataset
  Private mMyValue as Object

  Public Shadows Property DS as MyStronglyTypedDataset
    Get
      Return CType(MyBase.DS,MyStronglyTypedDataset)
    End Get
    Set (Value as MyStronglyTypedDataset)
      MyBase.DS=CType(Value,Dataset)
    End Set
  End Property

  Protected Overrides Sub MyExample
    MyBase.MyExample
    mMyValue=mds.MyTable.MyColumn
  End Sub
..
..
..
..
End Class

Of course, this won't work because CType doesn't work between Dataset as
MyStronglyTypedDataset.  But I think you can get the idea of what I am trying
to accomplish.

Thanks for the help,

Pat,

I get more and more the idea that what you call a usercontrol is not a
usercontrol.

A usercontrol is a kind of inherited or own written textbox, combobox etc.
Using the toolbox you can beside controls as well get other components as
dataset, adapters which you can place under the tag user controls. Is that
maybe (at least for me)   the confusing part.

What I now see is in my opinion a kind of strongly typed dataset.

I made once a very simple for for Klaus. Is that what you are looking for?

\\\needs a datagrid on a form
Private Sub Form1_Load(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles MyBase.Load
        Dim ds As New MyDataset
        For i As Integer = 0 To 10
            ds.KlausTableAddNew(New Object() {i.ToString, ChrW(i + 65)})
        Next
        DataGrid1.DataSource = ds.TableKlaus
    End Sub
End Class
///
\\\Dataset
Public Class MyDataset
    Inherits DataSet
    Sub New()
        MyBase.new()
        Dim dt As New DataTable("TableKlaus")
        Me.Tables.Add(dt)
        dt.Columns.Add("Klaus")
        dt.Columns.Add("Cor")
        dt = New DataTable("TableCor")
        Me.Tables.Add(dt)
        dt.Columns.Add("John")
        dt.Columns.Add("Herfried")
    End Sub
    Public ReadOnly Property TableKlaus() As DataTable
        Get
            Return Me.Tables("TableKlaus")
        End Get
    End Property
    Public ReadOnly Property TableCor() As DataTable
        Get
            Return Me.Tables("TableCor")
        End Get
    End Property
    Public Sub KlausTableAddNew(ByVal obj As Object())
        Dim dr As DataRow = Me.TableKlaus.NewRow
        dr.ItemArray = obj
        Me.TableKlaus.Rows.Add(dr)
    End Sub
End Class
///
I hope this helps a little bit?

Cor

Cor,

Thanks for your reply.  However, I'm don't really know how to apply it to my
situation, indeed even if it DOES apply.  Perhaps my example was too
abstract.  Here is the situation:  I have designed a number of UserControls
that I call data entry panels.  They all inherit from one base UserControl. 
The base control has, for example, a "Save", a "New, a "Delete", and a
"Print" button, as well as a checkbox (viewed as a button) that puts the
panel in or out of "Edit" mode.  Since each of the "data entry panels" is
used for entering data into different datasources, they each have their own
strongly typed data set as well as their own textboxes and/or other
appropriate controls.  The base control implements many methods that are
overridable by the data entry panels.  For example:

Class BaseUserControl

  Private mfInEdit As Boolean=False

  Protected Property InEdit As Boolean
    Get
      return mfInEdit
    End Get
    Set (Value As Boolean)
      If Value<>mfInEdit then
        RaiseEvent  InEditChanging(Me, New EventArgs)
        mfInEdit=Value
        OnInEditChanged
        RaiseEvent InEditChanged(Me, New EventArgs)
      End If
    End Set
  End Property

  Protected Sub ColumnChanging
..
..
..
  End Sub

  Protected Overridable Sub OnInEditChanged
  .
  .
  .
  End Sub
..
..
..
End Class

Class DataEntryPanel1
  Inherits BaseUserControl

  Protected Overrides Sub OnInEditChanged
        If InEdit Then
            AddHandler MyDataSet1.MyDataTable1.ColumnChanging, New
DataColumnChangeEventHandler(AddressOf MyBase.ColumnChanging)
        Else
            RemoveHandler MyDataSet1.MyDataTable1.ColumnChanging, New
DataColumnChangeEventHandler(AddressOf MyBase.ColumnChanging)
        End If
  End Sub
..
..
..
End Class

Since all the data entry panels want to do this same thing (only on
different strongly typed datasets) it seems it would be nice to generalize
and move the overriding InEditChanged code into the base class, for example:

Protected Overridable Sub OnInEditChanged
        If InEdit Then
            AddHandler mBaseDataset.Tables(mstrTableName).ColumnChanging,
New DataColumnChangeEventHandler(AddressOf MyBase.ColumnChanging)
        Else
            RemoveHandler mBaseDataset.Tables(mstrTableName).ColumnChanging,
New DataColumnChangeEventHandler(AddressOf MyBase.ColumnChanging)
        End If
End Sub

Where mBaseDataset would be an untyped dataset and a property of the
BaseUserControl (shadowed by the inheriting data entry panels), and 
mstrTableName would be a string property (value provided by the inheriting
data entry panels) of the BaseUserControl.

Thanks for any help,

Pat
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Pat,

It is called one of the worst things that you can do is when you mix data
with controls.

Don't ask me to give you an example for that which will than be forever as a
sample from Cor on Internet.

Cor

OK.  That helps a lot!!

Thanks Cor,

Pat

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