Having a heck of a time getting object property values into textboxes

Question

I am new to the MVVM design pattern, and I am working on a project to automate shipping processes.

The particular problem that I am having is I have a UserControl (my EditShipmentView) which when it loads, assigns it's ViewModel to its DataContext. The ViewModel is passed a recordID which it uses to pull the entity that represents a shipment. It does this successfully, as I can see it in Mole (visualizer).

Below is a XAML fragment showing the first couple of TextBoxes, and what I thought the bindings should look like.

<local:SnazzyForm Background="#FF318AE1">

    <Grid Margin="6,0,0,0">

        <TabControl Style="{DynamicResource SnazzyTabControl}" TabStripPlacement="Left" Background="{x:Null}" BorderBrush="{x:Null}" Margin="0,0,0,50">
            <TabItem Header="Overview" Style="{DynamicResource TransparentTabItems}">
                <Grid Margin="6,0,0,0">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="*"/>
                        <ColumnDefinition Width="*"/>
                    </Grid.ColumnDefinitions>

                    <StackPanel DataContext="{Binding Path=ShipmentRecord}">
                        <TextBlock HorizontalAlignment="Left" Text="Contact Info" TextWrapping="Wrap" Style="{DynamicResource TitleText}"/>
                        <Path Fill="#FFFFB900" Stretch="Fill" HorizontalAlignment="Left" Width="200" Height="2" Data="M0,16.5 L278.5,16.5" Stroke="#FFFFB900"/>
                        <StackPanel Margin="0,10,0,0">
                            <Grid Margin="0,16,0,0">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width=".40*"/>
                                    <ColumnDefinition Width=".60*"/>
                                </Grid.ColumnDefinitions>
                                <TextBlock HorizontalAlignment="Right" Text="Company" TextWrapping="Wrap" VerticalAlignment="Top" Style="{DynamicResource FieldLabel}" TextAlignment="Right" Margin="0,2,9,0"/>
                                <TextBox Text="{Binding Path=CompanyName, Mode=TwoWay, UpdateSourceTrigger=LostFocus, NotifyOnValidationError=True, ValidatesOnDataErrors=True, ValidatesOnExceptions=True}" TextWrapping="Wrap" d:LayoutOverrides="Height" Grid.Column="1"/>
                            </Grid>
                            <Grid Margin="0,16,0,0">
                                <Grid.ColumnDefinitions>
                                    <ColumnDefinition Width=".40*"/>
                                    <ColumnDefinition Width=".60*"/>
                                </Grid.ColumnDefinitions>
                                <TextBlock HorizontalAlignment="Right" Text="Contact" TextWrapping="Wrap" VerticalAlignment="Top" Style="{DynamicResource FieldLabel}" TextAlignment="Right" Margin="0,2,9,0"/>
                                <TextBox Grid.Column="1" Text="{Binding Path=ContactName}" TextWrapping="Wrap" d:LayoutOverrides="Height"/>
                            </Grid>

So, to recap... EditShipmentView (Inherits from SnazzyForm) DataContext is EditShipmentViewModel EditShipmentViewModel.ShipmentRecord is populated (successfully) with a shipment object ShipmentRecord.CompanyName is a string which obviously should return the name of a company.

Keep in mind this is only my most recent attempt. Previously I have not bound the Stackpanels DataContext and had the Textboxes bound as such "{Binding Path=ShipmentRecord.CompanyName}", and what seems like a hundred different variations. What hair I have left is rapidly receding. Please, think of my hair, send help.

Cory

Answer 1

Show us your code? Chances are your view model is just not notifying the view when it changes. If your bindings are incorrect (not resolved) you will see output to that effect in Visual Studio's debug output window. Check that as well.

HTH,
Kent

Answer 2

Make sure that EditShipmentViewModel (likely culprit) and ShipmentRecord implement INotifyPropertyChanged.

If the data is loaded after the initial view is setup, and the EditShipmentViewModel class doesn't raise a PropertyChanged event for ShipmentRecord, then the View (xaml) will never know to update the binding, and you'll see an empty string.