MVVM combobox Selected item binding in listview - wpf

Question

I am trying to bind combo box inside of a list view.
Here is the Xaml:
<UserControl
<UserControl.Resources>
<Style TargetType="ListViewItem">
<Style.Triggers>
<Trigger Property="IsKeyboardFocusWithin" Value="true">
<Setter Property="IsSelected" Value="true" />
</Trigger>
</Style.Triggers>
</Style>
</UserControl.Resources>
<DockPanel MinWidth="724" Height="387" DataContext="{Binding DeviceDiagnosticsMainVeiwModel}">
<globals:SaveNotificationPopup IsOpen="{Binding IsSaveNotificationPopupOpen}" SaveCommand="{Binding SaveCommand}" CancelCommand="{Binding CloseSaveNotificationPopup}" Placement="Relative" VerticalOffset="300" HorizontalOffset="200" />
<StackPanel>
<Grid Width="250" HorizontalAlignment="Left" Margin="10,10,0,0">
<Grid.RowDefinitions>
<RowDefinition Height="Auto" MinHeight="23" />
<RowDefinition Height="Auto" MinHeight="23" />
</Grid.RowDefinitions>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="100" />
<ColumnDefinition Width="150" />
</Grid.ColumnDefinitions>
<Label Grid.Row="0" Content="{x:Static ml:MultiLang._2001}" x:Name="ML_0209" />
<Label Grid.Row="1" Content="{x:Static ml:MultiLang._2009}" x:Name="ML_0211" />
<ComboBox Grid.Column="1" Grid.Row="0" ItemsSource="{Binding Manufacturers}" DisplayMemberPath="WorkingPlace" SelectedValuePath="PersonCode" SelectedValue="{Binding Path=ManufacturerID, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
<ComboBox Grid.Column="1" Grid.Row="1" ItemsSource="{Binding Devices}" DisplayMemberPath="Model" SelectedValue="{Binding Path=SelectedDevice, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />
</Grid>
<ListView DockPanel.Dock="Top" Margin="10,25,10,10" Width="460" ScrollViewer.HorizontalScrollBarVisibility="Hidden" HorizontalAlignment="Left" ItemsSource="{Binding CurrentDeviceDiagnostics}" SelectedItem="{Binding SelectedDeviceDiagnostics}" BorderThickness="1">
<ListView.View>
<GridView>
<GridViewColumn Header="Command" Width="180" x:Name="ML_0007">
<GridViewColumn.CellTemplate>
<DataTemplate>
<TextBox Text="{Binding DiagnosticsCommand, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" FontSize="12" Margin="0 5 0 0" Width="165" TextAlignment="Center" />
</DataTemplate>
</GridViewColumn.CellTemplate>
</GridViewColumn>
<GridViewColumn Header="Name" Width="180" x:Name="ML_0010">
<GridViewColumn.CellTemplate>
<DataTemplate>
<TextBox Text="{Binding DiagnosticsName, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}" FontSize="12" Margin="0 5 0 0" Width="165" TextAlignment="Center" />
</DataTemplate>
</GridViewColumn.CellTemplate>
</GridViewColumn>
<GridViewColumn Header="Units" Width="100" x:Name="ML_0013">
<GridViewColumn.CellTemplate>
<DataTemplate>
<ComboBox ItemsSource="{Binding Units}" DisplayMemberPath="UnitName" SelectedValuePath="UnitCode" SelectedValue="{Binding DiagnosticsUnit, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" Height="23" HorizontalAlignment="Left" VerticalAlignment="Top" Width="85" Margin="0,1,0,0" />
</DataTemplate>
</GridViewColumn.CellTemplate>
</GridViewColumn>
</GridView>
</ListView.View>
</ListView>
<ContentControl DockPanel.Dock="Top" Content="{Binding AddNewCAView}" />
<!-- No Diagnodtics message-->
<globals:NoItemsMessage DockPanel.Dock="Top" Visibility="{Binding NoDiagnosticsVisibility}" HorizontalAlignment="Left" Margin="10" Width="360" Height="40" Message="{x:Static ml:MultiLang._742}" x:Name="ML_0017" />
<!-- delete popup -->
<globals:DeletePopup IsOpen="{Binding IsConfirmDeletePopupOpen}" Message1="{x:Static ml:MultiLang._746}" DeleteCommand="{Binding DeleteCommand}" CancelCommand="{Binding CancelDeleteCommand}" Placement="Center" VerticalOffset="-200" HorizontalOffset="200" x:Name="ML_0018" />
</StackPanel>
</DockPanel>
</UserControl>
The Dock Panel binds to : DataContext="{Binding DeviceDiagnosticsMainVeiwModel}"
The list view binds are :
ItemsSource="{Binding CurrentDeviceDiagnostics}" SelectedItem="{Binding SelectedDeviceDiagnostics}"
and both CurrentDeviceDiagnostics and SelectedDeviceDiagnostics are members of DeviceDiagnosticsMainVeiwModel.
One text box (for example) in the list view bind like this :
Text="{Binding DiagnosticsCommand, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True}"
CurrentDeviceDiagnostics is an observble collection of DeviceDiagnosticsVeiwModel which contains DiagnosticsCommand.
And works just fine (both of the textboxes).
The checkbox binds like this:
ItemsSource="{Binding Units}" DisplayMemberPath="UnitName" SelectedValuePath="UnitCode" SelectedValue="{Binding DiagnosticsUnit, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
And Units and DiagnosticsUnit are also members of DeviceDiagnosticsVeiwModel.
The Item source works fine and populated the way i need.
The problem is with the selected item... its initialized as empty although DiagnosticsUnit has an integer value.
Funny thing is that if I choose something from the combobox, the code goes to the DiagnosticsUnit property to the set function, so I'm not sure abou t this problem...
Even if I will change the combobox to a textbox using DiagnosticsUnit , it will work !
I used a lots of mvvm comboboxes and didnt have any binding problems but its the first time i have a combocox inside of a list view...
Please help me.
Thank you all !!!

Answer 1

Let's break this down... you said:
both CurrentDeviceDiagnostics and SelectedDeviceDiagnostics are members of DeviceDiagnosticsMainViewModel.
That's as it should be. Then you said:
CurrentDeviceDiagnostics is an ObservableCollection<DeviceDiagnosticsViewModel>
Therefore the data bindings from inside the CellTemplates should point to properties from the DeviceDiagnosticsViewModel class as you correctly pointed out.
Therefore, looking at your ComboBox code below, I can only think of two possible reasons why this wouldn't work:
<ComboBox ItemsSource="{Binding Units}" DisplayMemberPath="UnitName"
SelectedValuePath="UnitCode" SelectedValue="{Binding DiagnosticsUnit, Mode=TwoWay,
UpdateSourceTrigger=PropertyChanged}" Height="23" HorizontalAlignment="Left"
VerticalAlignment="Top" Width="85" Margin="0,1,0,0" />
One suggestion would be to use the ComboBox.SelectedItem property instead and to data bind to an instance of the same type as your Units collection... however, if that is just a collection of ints, then this step wouldn't help. The only other thing would be to ensure that you have correctly implemented the INotifyPropertyChanged interface in the DeviceDiagnosticsViewModel class.

Answer 2

O.K
I finally found the problem !
It wasn't a binding problem.
this is very silly.
i had this code
public void GetItems()
{
_devicesDiagnostics = new ObservableCollection<DeviceDiagnosticsVeiwModel>(
(from dd in _dal.GetItems()
orderby dd.DeviceID
select new DeviceDiagnosticsVeiwModel(dd)
{
ObjectStatus = Status.NoChange,
Units = _manager.UnitRepository.Units
}
) .ToObservableCollection<DeviceDiagnosticsVeiwModel>()
);
}
The Units is a member in the view model (DeviceDiagnosticsVeiwModel) and it's actually the comboboxs item source.
Inside of DeviceDiagnosticsVeiwModel there's an int property which is the selected item. It didnt load it right.
The correct code will be
public void GetItems()
{
_devicesDiagnostics = new ObservableCollection<DeviceDiagnosticsVeiwModel>(
(from dd in _dal.GetItems()
orderby dd.DeviceID
select new DeviceDiagnosticsVeiwModel(dd)
{
ObjectStatus = Status.NoChange,
Units = new ObservableCollection<UnitViewModel>(this.Units),
}
)
.ToObservableCollection<DeviceDiagnosticsVeiwModel>()
);
}
I had to give every object a new list. It worked.