"Richard Mueller" <RichardMuel***@discussions.microsoft.com> wrote in
message news:0DDE9F39-F174-44E2-8F8C-6176F4ED484D@microsoft.com...
> I've seen this problem posted several times, but have not yet seen a
> solution.  I make a connection to a SQL database and use a DataAdapter
> object
> to fill a DataSet object with several tables. A DataRelation object links
> the
> tables by an ID column. I bind the parent table to a combo box and a child
> table to a DataGrid control using a DataView object. I want the DataGrid
> control to reflect the selection in the combo box. For the combo box,
> DisplayMember is a text string while ValueMember is the ID field
> (integer).
> In brief:
>
> Private Sub Form1_Load(....)
>    ' Connect to database, populate Tables in DataSet,
>    ' setup DataViews, and define DataRelations.
>    Call Populate()
>
>    ComboBox1.DataSource = MyDataSet.Tables(0)
>    ComboBox1.DisplayMember = MyDataSet.Tables(0).Columns(1).ColumnName
>    ComboBox1.ValueMember = MyDataSet.Tables(0).Columns(0).ColumnName
>    Me.BindingContext(MyDataSet.Tables(0)).Position = 0
>
>    Dim strFilter As String
>    strFilter = "ID = " & ComboBox1.SelectedValue
>    MyDataView.RowFilter = strFilter
>    DataGrid1.DataSource = MyDataView
> End Sub
>
> Private Sub ComboBox1_SelectedValueChanged(....)
>    Dim strFilter As String
>    If (ComboBox1.SelectedIndex <> -1) Then
>        strFilter = "ID = " & ComboBox1.SelectedValue
>        MyDataView.RowFilter = strFilter
>    End If
> End Sub
>
> Strangely, the code works if I comment out the
> ComboBox1_SelectedValueChanged sub. I can hard code in Form1_Load to
> select
> the first (index=0), or any other item in the combo box, and the DataGrid
> reflects the correct item. But of course I cannot select another item in
> the
> combo box and have the DataGrid reflect this. The error is raised in
> CombBox1_SelectedValueChanged on the statement:
>
> strFilter = "ID = " & ComboBox1.SelectedValue
>
> and the error is "Cast from type 'DataRowView' to type 'String' is not
> valid. I've tried to use ToString and CStr to no avail. I think the key is
> that I assign a DataSource to the combo box, plus the DisplayMember and
> ValueMember properites, then attempt to use the SelectedValue property
> when
> the user makes a selection. Any ideas?

> Note. My code is based on "Using a Data Set with Tables in a Parent-Child
> Relationship" from Chapter 10 (pg. 402-408) of "Programming Microsoft SQL
> Server 2000 with Microsoft Visual Basic .NET" by Rick Dobson.
>
> Richard

"Bart Mermuys" wrote:

> Hi,
>
> "Richard Mueller" <RichardMuel***@discussions.microsoft.com> wrote in
> message news:0DDE9F39-F174-44E2-8F8C-6176F4ED484D@microsoft.com...
> > I've seen this problem posted several times, but have not yet seen a
> > solution.  I make a connection to a SQL database and use a DataAdapter
> > object
> > to fill a DataSet object with several tables. A DataRelation object links
> > the
> > tables by an ID column. I bind the parent table to a combo box and a child
> > table to a DataGrid control using a DataView object. I want the DataGrid
> > control to reflect the selection in the combo box. For the combo box,
> > DisplayMember is a text string while ValueMember is the ID field
> > (integer).
> > In brief:
> >
> > Private Sub Form1_Load(....)
> >    ' Connect to database, populate Tables in DataSet,
> >    ' setup DataViews, and define DataRelations.
> >    Call Populate()
> >
> >    ComboBox1.DataSource = MyDataSet.Tables(0)
> >    ComboBox1.DisplayMember = MyDataSet.Tables(0).Columns(1).ColumnName
> >    ComboBox1.ValueMember = MyDataSet.Tables(0).Columns(0).ColumnName
> >    Me.BindingContext(MyDataSet.Tables(0)).Position = 0
> >
> >    Dim strFilter As String
> >    strFilter = "ID = " & ComboBox1.SelectedValue
> >    MyDataView.RowFilter = strFilter
> >    DataGrid1.DataSource = MyDataView
> > End Sub
> >
> > Private Sub ComboBox1_SelectedValueChanged(....)
> >    Dim strFilter As String
> >    If (ComboBox1.SelectedIndex <> -1) Then
> >        strFilter = "ID = " & ComboBox1.SelectedValue
> >        MyDataView.RowFilter = strFilter
> >    End If
> > End Sub
> >
> > Strangely, the code works if I comment out the
> > ComboBox1_SelectedValueChanged sub. I can hard code in Form1_Load to
> > select
> > the first (index=0), or any other item in the combo box, and the DataGrid
> > reflects the correct item. But of course I cannot select another item in
> > the
> > combo box and have the DataGrid reflect this. The error is raised in
> > CombBox1_SelectedValueChanged on the statement:
> >
> > strFilter = "ID = " & ComboBox1.SelectedValue
> >
> > and the error is "Cast from type 'DataRowView' to type 'String' is not
> > valid. I've tried to use ToString and CStr to no avail. I think the key is
> > that I assign a DataSource to the combo box, plus the DisplayMember and
> > ValueMember properites, then attempt to use the SelectedValue property
> > when
> > the user makes a selection. Any ideas?
>
> You're probely getting this error because SelectedValueChanged fires after
> setting the ComboBox.DataSource but before you have set the
> ComboBox.ValueMember.  So at that point SelectedValue returns a DataRowView.
> So you could change it to:
>
> Private Sub ComboBox1_SelectedValueChanged(....)
>   Dim strFilter As String
>   If (ComboBox1.SelectedIndex <> -1) AndAlso _
>       (ComboBox1.ValueMember<>"") Then
>        strFilter = "ID = " & ComboBox1.SelectedValue
>         MyDataView.RowFilter = strFilter
>    End If
> End Sub
>
> BUT, if you have a DataRelation between the two DataTables, then you don't
> need to do that, you can let the child rows be _automatically_ filtered.
> All you have to do is bind the DataGrid to the same DataSource as the
> ComboBox and set DataGrid.DataMember to the name of the DataRelation between
> them:
>
> Private Sub Form1_Load(....)
>   ' Connect to database, populate Tables in DataSet,
>   ' setup DataViews, and define DataRelations.
>   Call Populate()
>
>    ComboBox1.DataSource = MyDataSet.Tables(0)
>    ComboBox1.DisplayMember = MyDataSet.Tables(0).Columns(1).ColumnName
>    ComboBox1.ValueMember = MyDataSet.Tables(0).Columns(0).ColumnName
>
>    DataGrid1.DataSource = MyDataSet.Tables(0)
>    DataGrid1.DataMember = "NameOfRelationBetweenTables"
> End Sub
>
> This way the DataGrid should be auto filtered when you change ComboBox
> selection.
>
>
> HTH,
> Greetings
>
>
>
> > Note. My code is based on "Using a Data Set with Tables in a Parent-Child
> > Relationship" from Chapter 10 (pg. 402-408) of "Programming Microsoft SQL
> > Server 2000 with Microsoft Visual Basic .NET" by Rick Dobson.
> >
> > Richard
>
>
>
>
>
>