Comboboxes in GridView are synchronized instead of bound to the value from the database

Question

I have tried to set up combo boxes in the gridview but all the combo boxes have the same value in them instead of the value from the database. I am using entity framework and WPF. There is a parent child relationship between two tables but the source for the combo box is a separate table with names and IDs for tags. I have been looking all day. Hopefully this won't be too easy to solve.

The "Tag" Column displays the combo box. The Column "Tag ID" displays the value from the database. When I display the data the TagID Changes in diffrent rows but the Tag column is the same (the first choice) in all the rows. When I change one combo box they all change. I can't see where they are hooked together. Any assistance you can provide would be appreciated. (Buler?)

Here is the XAML

<Window x:Class="MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="MainWindow" Height="372" Width="675" mc:Ignorable="d" xmlns:d="http://schemas.microsoft.com/expression/blend/2008" xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" xmlns:my="clr-namespace:TagFinanceWPF">
<Window.Resources>
    <CollectionViewSource x:Key="TransactionsViewSource" d:DesignSource="{d:DesignInstance my:Transaction, CreateList=True}" />
    <CollectionViewSource x:Key="TransactionsTransactionTagsViewSource" Source="{Binding Path=TransactionTags, Source={StaticResource TransactionsViewSource}}" />
    <CollectionViewSource x:Key="TagLookup" />
</Window.Resources>
<Grid DataContext="{StaticResource TransactionsViewSource}">
    <ListView ItemsSource="{Binding Source={StaticResource TransactionsTransactionTagsViewSource}}" Margin="12" Name="TransactionTagsListView" SelectionMode="Single">
        <ListView.ItemContainerStyle>
            <Style>
                <Setter Property="Control.HorizontalContentAlignment" Value="Stretch" />
                <Setter Property="Control.VerticalContentAlignment" Value="Stretch" />
            </Style>
        </ListView.ItemContainerStyle>
        <ListView.View>
            <GridView>
                <GridViewColumn x:Name="TransactionIDColumn1" Header="Transaction ID" Width="80">
                    <GridViewColumn.CellTemplate>
                        <DataTemplate>
                            <Label Content="{Binding Path=TransactionID}" Margin="6,-1,-6,-1" />
                        </DataTemplate>
                    </GridViewColumn.CellTemplate>
                </GridViewColumn>
                <GridViewColumn x:Name="TagIDColumn" Header="Tag" Width="80">
                    <GridViewColumn.CellTemplate>
                        <DataTemplate>
                            <ComboBox Margin="-6,-1" 
                                      ItemsSource="{Binding Source={StaticResource TagLookup}}" 
                                      DisplayMemberPath="TagName" 
                                      SelectedValuePath="TagID"
                                      SelectedValue="{Binding TagID}" 
                                      IsReadOnly="True">
                            </ComboBox>
                        </DataTemplate>
                    </GridViewColumn.CellTemplate>
                </GridViewColumn>

                <GridViewColumn x:Name="TagIDColumn2" Header="Tag ID" Width="80">
                    <GridViewColumn.CellTemplate>
                        <DataTemplate>
                            <Label Content="{Binding Path=TagID}" />
                        </DataTemplate>
                    </GridViewColumn.CellTemplate>
                </GridViewColumn>
            </GridView>
        </ListView.View>
    </ListView>
</Grid>

The VB code is:

Class MainWindow

Dim BentleyvideoEntities As TagFinanceWPF.bentleyvideoEntities = New TagFinanceWPF.bentleyvideoEntities()

Private Function GetTransactionsQuery(ByVal BentleyvideoEntities As TagFinanceWPF.bentleyvideoEntities) As System.Data.Objects.ObjectQuery(Of TagFinanceWPF.Transaction)

    Dim TransactionsQuery As System.Data.Objects.ObjectQuery(Of TagFinanceWPF.Transaction) = BentleyvideoEntities.Transactions
    'Update the query to include TransactionTags data in Transactions. You can modify this code as needed.
    TransactionsQuery = TransactionsQuery.Include("TransactionTags")
    'Returns an ObjectQuery.
    Return TransactionsQuery
End Function

Private Sub Window_Loaded(ByVal sender As System.Object, ByVal e As System.Windows.RoutedEventArgs) Handles MyBase.Loaded

    'Load data into Transactions. You can modify this code as needed.
    Dim TransactionsViewSource As System.Windows.Data.CollectionViewSource = CType(Me.FindResource("TransactionsViewSource"), System.Windows.Data.CollectionViewSource)
    Dim TransactionsQuery As System.Data.Objects.ObjectQuery(Of TagFinanceWPF.Transaction) = Me.GetTransactionsQuery(BentleyvideoEntities)
    TransactionsViewSource.Source = TransactionsQuery.Execute(System.Data.Objects.MergeOption.AppendOnly)
    'Load data into Tags. You can modify this code as needed.


    Dim customerList = From c In BentleyvideoEntities.Tags _
                                  Order By c.TagName

    Dim custSource = CType(Me.FindResource("TagLookup"), CollectionViewSource)
    custSource.Source = customerList.ToList()

End Sub

End Class

Answer 1

I found this while researching your issue and it sounds like the exact same issue you are experiencing.

Snippit from link:

I'm not sure if this will help, but I was reading in Chris Sells 'Windows Forms Binding in C#, footnote, page 482', that the data source is bound to each combobox and is managed by a common Binding manager which in turn is part of a Binding Context. The Binding amager keeps all comboboxes synchronized to the same row in the database. However, if each combobox has a different Binding context, hence a diferent Binding Manager, then the combo boxes can show different rows from the same data source.

Based on this second article (and the suggested solution) you would need to use the row databinding event to set up the combobox's binding so that a new instace of the binding manager is created for each row bind.