Question

My application uses WPF for the presentation layer. I have a UserControl in my code, whose XAML is shown below:

<UserControl x:Class="CarSystem.CustomControls.ReadPushPin"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:cs="clr-namespace:CarSystem.CustomControls"
             mc:Ignorable="d"
             DataContext="{Binding Path=Read, RelativeSource={RelativeSource Self}}"
             d:DesignHeight="30"
             d:DesignWidth="30">

    <UserControl.Resources>
        <cs:BooleanToVisibilityConverter x:Key="BoolToVisibility" True="Visible" False="Collapsed" />
        <cs:DateConverterForRadDateTimePicker x:Key="DateConverter" />
    </UserControl.Resources>

    <Image Name="MarkerImage"
           Source="{Binding Path=Source, RelativeSource={RelativeSource AncestorType={x:Type cs:ReadPushPin}}}">
        <Image.ToolTip>
            <Grid>
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width="Auto" />
                    <ColumnDefinition Width="*" />
                </Grid.ColumnDefinitions>
                <Grid.RowDefinitions>
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <Image Grid.Column="0"
                       Grid.ColumnSpan="2"
                       Grid.Row="0"
                       Height="45"
                       HorizontalAlignment="Center"
                       Source="{Binding Path=ThumbnailImage, RelativeSource={RelativeSource AncestorType={x:Type cs:ReadPushPin}}}"
                       Visibility="{Binding Converter={StaticResource BoolToVisibility}, Path=HasThumbnail, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type cs:ReadPushPin}}}"
                       Width="60" />
                <TextBlock Grid.Column="0"
                           Grid.Row="1"
                           HorizontalAlignment="Right"
                           Text="Plate:" />
                <StackPanel Grid.Column="1"
                            Grid.Row="1"
                            HorizontalAlignment="Left"
                            Orientation="Horizontal">
                    <TextBlock Text="{Binding Path=Plate}" />
                    <TextBlock Text=", " />
                    <TextBlock Text="{Binding Path=State}" />
                </StackPanel>
                <TextBlock Grid.Column="0"
                           Grid.Row="2"
                           HorizontalAlignment="Right"
                           Text="Time:" />
                <TextBlock Grid.Column="1"
                           Grid.Row="2"
                           HorizontalAlignment="Left"
                           Text="{Binding Converter={StaticResource DateConverter}, Path=TimeStamp}" />
                <TextBlock Grid.Column="0"
                           Grid.Row="3"
                           HorizontalAlignment="Right"
                           Text="Nearest Address:" />
                <TextBlock Grid.Column="1"
                           Grid.Row="3"
                           HorizontalAlignment="Left"
                           Text="{Binding Path=NearestAddress, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type cs:ReadPushPin}}}" />
                <TextBlock Grid.Column="0"
                           Grid.Row="4"
                           HorizontalAlignment="Right"
                           Text="Cross Street:" />
                <TextBlock Grid.Column="1"
                           Grid.Row="4"
                           HorizontalAlignment="Left"
                           Text="{Binding Path=CrossStreet, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type cs:ReadPushPin}}}" />
            </Grid>
        </Image.ToolTip>
    </Image>
</UserControl>

There are a number of DependencyProperties defined in the code-behind that are bound to the various controls in the Image’s ToolTip property.

My problem is that the bindings on the ThumbnailImage, HasThumbnail, NearestAddress, and CrossStreet properties aren’t working. I see errors like the following in the Debug Output window when the program runs:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='CarSystem.CustomControls.ReadPushPin', AncestorLevel='1''. BindingExpression:Path=CrossStreet; DataItem=null; target element is 'TextBlock' (Name=''); target property is 'Text' (type 'String')

What am I doing wrong? How do I get the bindings to work?

Tony

Answer 1

I believe that the problem has to do with the ToolTip not being in the same visual tree as the control it belongs to.

I solved the problem by adding properties to the view model object for each control in the ToolTip template. As I needed to include a thumbnail image, and I’m storing images in my database as byte arrays, I wrote a class that implements IValueConverter that converts a byte array into a BitmapImage.

This all works. Thanks anyways.