Develop Reference

C# WPF Changing ContentControl Content based on DataTrigger not working

I am trying, with no luck, to change the content of a content control based upon a DataTrigger, that checks a binding to see if it matches a type, and if it does change the contentcontrols displayed content.
In short, I want this ContentControl's Content to change if the Source is a certain type. I have attempted to do this using Styles / DataTriggers
<ContentControl>
<ContentControl.Content>
<TextBlock Name="CollectionControlTextBox1"
Tag="."
PreviewMouseDown="CollectionControlDefaultDockPanel_MouseButtonDown"
PreviewMouseUp="CollectionControlTextBox1_PreviewMouseUp"
MouseMove="CollectionControlDefaultDockPanel_MouseMove"
Drop="CollectionControlDefaultDockPanel_Drop"
Foreground="{Binding Meta.ColorBrush, Mode=OneWay, TargetNullValue={StaticResource TextBrush}, FallbackValue={StaticResource TextBrush}}"
AllowDrop="True"
MinHeight="20"
Padding="5 2 0 0"
KeyboardNavigation.IsTabStop="False"
Focusable="True"
TextTrimming="CharacterEllipsis"
ContextMenu="{Binding ParentControl.MemberContextMenu, Mode=OneWay}"
Text="{Binding DisplayName, Mode=OneWay}">
<TextBlock.CommandBindings>
<CommandBinding Command="{x:Static iugo:EditorCommands.Metadata}" Executed="Metadata" />
</TextBlock.CommandBindings>
</TextBlock>
</ContentControl.Content>
<ContentControl.Style>
<Style TargetType="ContentControl">
<Style.Triggers>
<DataTrigger Binding="{Binding Source, Converter={StaticResource IsAssociation}}" Value="True">
<Setter Property="Content">
<Setter.Value>
<StackPanel Orientation="Horizontal">
<TextBlock Text="{Binding IdEntry.Id}" ToolTip="{Binding IdEntry.Entry.Name}" FontSize="10" Foreground="{StaticResource DisabledTextBrush}" HorizontalAlignment="Center" Margin="0, 3, 0, 0"/>
<TextBlock Text="{Binding IdEntry.Entry.Name}" ToolTip="{Binding IdEntry.Entry.Name}" FontSize="13" Margin="5, 0, 0, 0"/>
</StackPanel>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>
I have tested that the converter: IsAssociation is correctly being hit, and is correctly the right value, but the Content does not change to a stackpanel as defined in the DataTrigger. I have confirmed this by using Visual Studios' Visual Tree, and it still links to the old content.

A directly set Content like
<ContentControl>
<Content>
...
</Content>
</ContentControl>
has higher value precedence than a value set by a Setter in a Style Trigger. Your DataTrigger is hence ignored.
Instead of directly setting the Content, move the initial value to another Setter:
<ContentControl>
<ContentControl.Style>
<Style TargetType="ContentControl">
<Setter Property="Content">
<Setter.Value>
<TextBlock ...>
...
</TextBlock>
</Setter.Value>
</Setter>
<Style.Triggers>
<DataTrigger ...>
<Setter Property="Content">
<Setter.Value>
<StackPanel Orientation="Horizontal">
...
</StackPanel>
</Setter.Value>
</Setter>
</DataTrigger>
</Style.Triggers>
</Style>
</ContentControl.Style>
</ContentControl>

Binding to data breaking on VirtualizingStackPanel

First of all, a disclaimer, I'm working with .net 3.5's virtualizingstackpanel. If you get different behavior in future versions let me know. It's relatively simple to set up a test case with listviews that you can test this against.
I have an itemcontainer style in a virtualizingstackpanel that binds the property IsSelected to the viewmodel.
When I Select an unselected item in the view model that is off screen, and then scroll to that item, both the datacontext (viewmode) and the actual listviewitem have the IsSelected Property as true (expected behavior). The trigger is properly applied to the listviewitem highlighting it.
However, when I deselect the datacontext for an item that is not in view and then scroll down until the item is in view, upon reaching the item and creating it, the item's datacontext now has IsSelected = true and the listviewitem's IsSelected property is also true, so the listviewitem ends up with a selection rectangle from the trigger(incorrect behavior).
It's almost as if the ListViewItem's Properties are all restored on creation of the item ( this makes sense to me, but then they should bind the datacontext's values to the item afterward).
But that doesn't seem to be happening. Moreover, after failing to deselect the item and scrolling back to find it selected. If i then select/desect it, the binding has no effect on the item.
I can see no logical reason why it would work when selecting an item in the viewmodel that is offscreen and not when I Deselect an item offscreen. In both cases, the newly created item should need to be rebound to the current value of the viewmodel. However, one works and the other doesn't.
Edit:
Ah ok, so I just can't use recycling mode and binding it seems. Thanks #devhedgehog. Would give you the bounty but you need an answer. I swear I tried that earlier, but maybe I was not handling click events in the bound listview before so that I was breaking the binding on physical selection or something. I do remember attempting both modes at one point, but probably had something else interfering so it wouldn't work. Anyway it works now.
Since you mentioned it, I would like to preferably avoid keeping unnecessary code and inherit from virtualizingstackpanel instead of virtualizing panel. But I want to be able to set the horizontal scroll extent, which requires me to reimplement Iscrollinfo. However, I was having trouble getting virtualizingstackpanel to interact nicely with iscrollinfo.
<ListView
x:Name="TestLV"
VerticalAlignment="Stretch"
HorizontalAlignment="Stretch"
Background="Green"
ItemsSource="{Binding Path=AddedItems, Mode=OneWay}"
SnapsToDevicePixels="True"
VirtualizingStackPanel.VirtualizationMode="Recycling"
VirtualizingStackPanel.IsVirtualizing="true"
ScrollViewer.IsDeferredScrollingEnabled="False"
Grid.Column ="4"
MouseDown="TestLV_MouseDown"
>
<ListView.ItemContainerStyle>
<Style TargetType="ListViewItem">
<Setter Property="IsSelected" Value="{Binding Path=IsSelected, Mode=OneWay}" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type ListViewItem}">
<Grid
x:Name="SignalGrid"
Background="Transparent"
>
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
</Grid.ColumnDefinitions>
<Grid.RowDefinitions>
<RowDefinition Height="Auto"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Border
Name="Bd"
BorderBrush="{TemplateBinding BorderBrush}"
BorderThickness="{TemplateBinding BorderThickness}"
Padding="{TemplateBinding Padding}"
SnapsToDevicePixels="true">
<ContentPresenter
x:Name="PART_Header"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"
/>
</Border>
<ItemsPresenter
x:Name="ItemsHost"
Grid.Row="1"
Grid.Column="0"
/>
</Grid>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected"
Value="false">
<Setter
TargetName="SignalGrid"
Property="Background"
Value="Transparent"
/>
</Trigger>
<Trigger Property="IsSelected"
Value="true">
<Setter
TargetName="SignalGrid"
Property="Background"
Value="Navy"
/>
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</ListView.ItemContainerStyle>
<ListView.ItemsPanel>
<ItemsPanelTemplate>
<VirtualizingStackPanel />
<!--<Components:VirtualizingTilePanel
ChildSize="{Binding Path=GraphHeight}"
/>-->
</ItemsPanelTemplate>
</ListView.ItemsPanel>
<ListView.Template>
<ControlTemplate>
<Grid >
<ScrollViewer
>
<ItemsPresenter />
</ScrollViewer>
</Grid>
</ControlTemplate>
</ListView.Template>
<!--Template Defining the layout of items in this treeview-->
<ListView.Resources>
<HierarchicalDataTemplate
ItemsSource ="{Binding Path = bits}"
DataType="{x:Type ViewModels:BusViewModel}"
>
<Grid>
<Components:CenteredTextBlock
x:Name="CommentTextBlock"
Foreground="Black"
BorderThickness="{Binding RelativeSource ={RelativeSource AncestorType={x:Type ListView}}, Path=BorderThickness}"
BorderBrush="{Binding RelativeSource ={RelativeSource AncestorType={x:Type ListView}}, Path=BorderBrush}"
HorizontalAlignment="Stretch"
Height="{Binding ElementName=graph_viewer, Path=GraphHeight, Mode=OneWay}"
>
<Components:CenteredTextBlock.MainText>
<MultiBinding Converter="{StaticResource StringConcatConverter}">
<Binding Path="Alias" />
<Binding Path="SignalValueAtPrimaryMarker" />
</MultiBinding>
</Components:CenteredTextBlock.MainText>
</Components:CenteredTextBlock>
</Grid>
</HierarchicalDataTemplate>
<DataTemplate
DataType="{x:Type ViewModels:BitViewModel}"
>
<Grid>
<Components:CenteredTextBlock
Foreground="Black"
BorderThickness="{Binding RelativeSource ={RelativeSource AncestorType={x:Type ListView}}, Path=BorderThickness}"
BorderBrush="{Binding RelativeSource ={RelativeSource AncestorType={x:Type ListView}}, Path=BorderBrush}"
HorizontalAlignment="Stretch"
Height="{Binding ElementName=graph_viewer, Path=GraphHeight, Mode=OneWay}">
<Components:CenteredTextBlock.MainText>
<MultiBinding Converter="{StaticResource StringConcatConverter}">
<Binding Path="Alias" />
<Binding Path="SignalValueAtPrimaryMarker" />
</MultiBinding>
</Components:CenteredTextBlock.MainText>
</Components:CenteredTextBlock>
</Grid>
</DataTemplate>
<DataTemplate
DataType="{x:Type ViewModels:SelectableItemViewModel}"
>
<Grid>
<Components:CenteredTextBlock
Foreground="Red"
BorderThickness="{Binding RelativeSource ={RelativeSource AncestorType={x:Type ListView}}, Path=BorderThickness}"
BorderBrush="{Binding RelativeSource ={RelativeSource AncestorType={x:Type ListView}}, Path=BorderBrush}"
HorizontalAlignment="Stretch"
Height="{Binding ElementName=graph_viewer, Path=GraphHeight, Mode=OneWay}"
MainText="{Binding Path = FullName}"
/>
</Grid>
</DataTemplate>
</ListView.Resources>
</ListView>

It seems strange that this question actually appears to have been answered, yet is listed as not having an answer. So I will post dev hedgehog's comment/answer here.
Please use standard VirtualizingStackPanel without your custom measure
logic. There is nothing you added special in your logic that
VirtualizingStackPanel cant do. And RecyclingMode should not be
Recycle but instead leave it out or change to Standard.

Combobox "Select Item" binding

I'm working on a few ComboBoxes that need a "select" property as the top option in WPF (c#)
At the moment I have the combobox's named and then populated in the code behind from a array string.
<ComboBox Width="150" x:Name="cmbTitle" Margin="3" SelectedIndex="0" />
.
cmbTitle.Items.Add("Select");
foreach (var title in Constants.Title)
cmbTitle.Items.Add(title);
My Issue is that the selectd Index will always be off by 1 of the index in the string.
After doing my research I see that this is a very prehistoric way of populating a combo box (WinFrom background). Constants seem to be stored in Enums in every example I have looked at so would like to move away from multiple string[]s.
What is my best way of binding an enum to a combobox while accommodating for a "select" option in WPF?
I've looked at half a dozen options today and I'm not too sure what other code examples to list.
It's quite a open question, but I'm quite lost.
Thanks in advance,
Oli

Values of an enumeration can be retrieved from Enum.GetValues(), and binding to a method is typically done using ObjectDataProvider. Here's an example of getting all BindingMode values:
<ObjectDataProvider x:Key="BindingModes" ObjectType="{x:Type sys:Enum}" MethodName="GetValues">
<ObjectDataProvider.MethodParameters>
<x:Type TypeName="BindingMode" />
</ObjectDataProvider.MethodParameters>
</ObjectDataProvider>
Now, we can bind ItemsSource of our ComboBox:
<ComboBox ItemsSource="{Binding Source={StaticResource BindingModes}}" />
Our control needs a new property for the prompt:
public class ExtendedComboBox : ComboBox
{
public static readonly DependencyProperty PromptProperty =
DependencyProperty.Register("Prompt", typeof(string), typeof(ExtendedComboBox), new PropertyMetadata(string.Empty));
public string Prompt
{
get { return (string)GetValue(PromptTextProperty); }
set { SetValue(PromptTextProperty, value); }
}
}
We can cheat a bit and place a TextBlock with the prompt inside our control, and hide it when there's an item selected. For this we rewrite ControlTemplate of the control with a new one containing the TextBlock. I modified template from there:
<Style x:Key="PromptTextBlock" TargetType="{x:Type TextBlock}" >
<Setter Property="Visibility" Value="Hidden" />
<Style.Triggers>
<DataTrigger Binding="{Binding SelectedItem, RelativeSource={RelativeSource TemplatedParent}}" Value="{x:Null}">
<Setter Property="Visibility" Value="Visible" />
</DataTrigger>
</Style.Triggers>
</Style>
<Style x:Key="PromptedComboBox" TargetType="{x:Type local:ExtendedComboBox}">
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="{x:Type local:ExtendedComboBox}">
<Grid>
<ToggleButton x:Name="DropDownToggle"
HorizontalAlignment="Stretch" VerticalAlignment="Stretch"
Margin="-1" HorizontalContentAlignment="Right"
IsChecked="{Binding IsDropDownOpen, Mode=TwoWay, RelativeSource={RelativeSource TemplatedParent}}">
<Path x:Name="BtnArrow" Height="4" Width="8"
Stretch="Uniform" Margin="0,0,4,0" Fill="Black"
Data="F1 M 300,-190L 310,-190L 305,-183L 301,-190 Z " />
</ToggleButton>
<ContentPresenter x:Name="ContentPresenter" Margin="6,2,25,2"
Content="{TemplateBinding SelectionBoxItem}"
ContentTemplate="{TemplateBinding SelectionBoxItemTemplate}"
ContentTemplateSelector="{TemplateBinding ItemTemplateSelector}">
</ContentPresenter>
<TextBox x:Name="PART_EditableTextBox"
Style="{x:Null}"
Focusable="False"
Background="{TemplateBinding Background}"
HorizontalAlignment="Left"
VerticalAlignment="Center"
Margin="3,3,23,3"
Visibility="Hidden"
IsReadOnly="{TemplateBinding IsReadOnly}"/>
<Popup x:Name="PART_Popup" IsOpen="{TemplateBinding IsDropDownOpen}">
<Border x:Name="PopupBorder"
HorizontalAlignment="Stretch" Height="Auto"
MinWidth="{TemplateBinding ActualWidth}"
MaxHeight="{TemplateBinding MaxDropDownHeight}"
BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="Black" Background="White" CornerRadius="3">
<ScrollViewer x:Name="ScrollViewer" BorderThickness="0" Padding="1">
<ItemsPresenter/>
</ScrollViewer>
</Border>
</Popup>
<TextBlock Margin="4,3,20,3" Text="{Binding PromptText, RelativeSource={RelativeSource TemplatedParent}}" Style="{StaticResource PromptTextBlock}"/>
</Grid>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
Combining, we have:
<local:ExtendedComboBox Style="{StaticResource PromptedComboBox}" Prompt="Select an item" ItemsSource="{Binding Source={StaticResource BindingModes}}" />

I think the best way to populate your ComboBox will be using IDictionary.
As an example, your code-behind:
public YourEnum SelectedOption { get; set; }
public IDictionary<string, YourEnum> Options = new Dictionary<string, YourEnum?>();
Options.Add("Select", null);
Options.Add("Option 1", YourEnum.Option1);
...
Options.Add("Option N", YourEnum.OptionN);
Your xaml file:
<ComboBox ItemsSource="{Binding Options, ...}" SelectedValue="{Binding SelectedOption, ...}" DisplayMemberPath="Key" SelectedValuePath="Value" />

ListBox , DataTemplate and Triggers

i got a DataTemplate for a listboxitem and i want to create a triger , so when a user click an item the background will change and also the label
my code:
<Window.Resources>
<Style x:Key="RoundedItem" TargetType="ListBoxItem">
<EventSetter Event="MouseDoubleClick" Handler="listViewItem_MouseDoubleClick" />
<Setter Property="Template">
<Setter.Value>
<ControlTemplate TargetType="ListBoxItem">
<Border Name="ItemBorder" CornerRadius="10" BorderBrush="Black" BorderThickness="1" Margin="1" Background="Transparent">
<Label Name="ItemLabel" Foreground="Red" >
<ContentPresenter />
</Label>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsSelected" Value="True">
<Setter TargetName="ItemBorder" Property="Background" Value="DeepSkyBlue" />
<Setter TargetName="ItemLabel" Property="Foreground" Value="Orange" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
<DataTemplate x:Key="TitleTemplate" DataType="models:Title" >
<StackPanel>
<Image Source="{Binding ThumbFilePath}" Width="50" HorizontalAlignment="Center"/>
<Label Content="{Binding Name}" HorizontalAlignment="Center" />
<TextBlock Text="{Binding Description}" HorizontalAlignment="Center" TextWrapping="Wrap" Padding="5,5,5,5"/>
</StackPanel>
</DataTemplate>
</Window.Resources>
What happend is that the TextBlock change his color and not the label..
anyone know why ?
Thanks.

The TextBlock inherits the Foreground definition from its parents in the visual tree. The Label, on the other hand, defines the Foreground in its default style.
Your approach is "non-WPF-like" - you shouldn't wrap the ContentPresenter in a Label control.
The right approach depends on whether you want all text in the item to change its Foreground, or just the label?
[In both cases, there's no apparent benefit to using a Label in the data template - so I'll assume that the label is changed to TextBlock.]
If the answer to the above question is that all text should be changed: in the ControlTemplate of the ListBoxItem, in the trigger for IsSelected, from the seccond setter remove TargetName="ItemLabel" so the final setter is:
<Setter Property="Foreground" Value="Orange" />
This will change the foreground of the item that will affect the foreground of both TextBlocks in the data template.
If you want to affect just one of the TextBlocks:
1. remove the setter for the foreground from the control template
2. add a trigger to your data template:
<DataTemplate>
<StackPanel>
<Image .../>
<TextBlock x:Name="Text01" ..../>
<TextBlock x:Name="Text02" ..../>
</StackPanel>
<DataTemplate.Triggers>
<DataTrigger Binding="{Binding IsSelected, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBoxItem}}}" Value="True">
<Setter TargetName="Text01" Property="Foreground" Value="Orange"/>
</DataTrigger>
</DataTemplate.Triggers>
</DataTemplate>
Side note: if you have to use Label control in your data template, bind its Foreground property to the Foreground of the list box item, like so:
<Label Foreground="{Binding Foreground, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBoxItem}}}"....../>
If this doesn't help, it means that your list box item inherits its foreground, so use:
<Label Foreground="{Binding TextElement.Foreground, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ListBoxItem}}}"....../>

I want to tack on to this that I was experiencing a similar problem where I'd added a ListBox.ItemTemplate to my ListBox, and the styling then did not apply to the text anymore.
What I was doing was trying to display a list of languages (CultureInfo) for the user to select from, however I wanted the native names to display, not the English name. For some reason, not all languages have their native names capitalized in their CultureInfo, and NativeName is the only instance of their name, so I needed to apply a function to the CultureInfo.NativeName to capitalize the names myself. To accomplish this, I added the ItemTemplate with a Data Template inside, on which I applied a converter.
<ListBox IsSynchronizedWithCurrentItem="True" VerticalAlignment="Center" MinHeight="200" x:Name="cbLanguages"
ItemsSource="{Binding Path=SupportedCultures, Mode=OneWay, Source={StaticResource CultureResourcesDS}}"
FontSize="24" HorizontalAlignment="Stretch" Width="300" Margin="10"
Style="{DynamicResource ListBoxTemplate}" ItemContainerStyle="{DynamicResource ListBoxItemStyle}">
<ListBox.ItemTemplate>
<DataTemplate>
<Label Content="{Binding Converter={StaticResource NativeNameConverter}}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
After a while of searching, I came across XAMeLi's answer here, and changed the Label I'd put in the DataTemplate to a TextBox, and the ListBoxItemStyle I'd created worked again.
Basically, Labels and TextBoxes have different traits that can be exploited, or can cause annoying issues in this case. Here's a good explanation with some examples of the differences: http://joshsmithonwpf.wordpress.com/2007/07/04/differences-between-label-and-textblock/

How do you bind a viewmodel which implements IDataErrorInfo to a UserControl and propagate the validation errors?

I've written a UserControl that exposes a few dependency properties to modify the layout of the control (i.e. think of it as a generic type-safe editor control - so my data types are dates (edited through a date picker), enumerations (edited through a combobox) and a numeric (edited through a textbox). I've also exposed the value of the 3 editor controls as a dependency property so that it can be databound.
The controls within the usercontrol all bind to the exposed dependency properties to get their values (with appropriate converters where necessary).
This control forms a tiny piece of a larger UI which binds to a viewmodel - the value to be edited, the datatype flag for the custom control and a list of possible valid values are all bound to an object in the viewmodel.
My problem is this: I've implemented IDataErrorInfo on the viewmodel and set the controls' bindings within the custom usercontrol to have ValidatesOnDataErrors=True, NotifyOnValidationError=True but the validation is not displaying.
This is the XAML for my usercontrol (there is no other code-behind logic beyond the dependency property declarations):
<UserControl.Resources>
<!-- Converters -->
<local:ValidationBooleanToImageConverter x:Key="ValidationBooleanToImageConverter"/>
<local:ValidationErrorToStringConverter x:Key="ValidationErrorToStringConverter"/>
<local:DataTypeToVisibilityConverter DataType="Date" x:Key="DateDataTypeToVisibilityConverter"/>
<local:DataTypeToVisibilityConverter DataType="Numeric" x:Key="NumericDataTypeToVisibilityConverter"/>
<local:DataTypeToVisibilityConverter DataType="Enumeration" x:Key="EnumerationDataTypeToVisibilityConverter"/>
<local:DateToStringConverter x:Key="DateToStringConverter"/>
<!-- Styles -->
<Style TargetType="{x:Type TextBox}">
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="True">
<Setter Property="ToolTip"
Value="{Binding RelativeSource={RelativeSource Self}, Path=(Validation.Errors).CurrentItem, Converter={StaticResource ResourceKey=ValidationErrorToStringConverter}}"/>
</Trigger>
</Style.Triggers>
</Style>
</UserControl.Resources>
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition Width="16"/>
</Grid.ColumnDefinitions>
<toolkit:DatePicker Height="25" Margin="0,0,5,0" Visibility="{Binding Path=DataType, ElementName=UserControl, Converter={StaticResource ResourceKey=DateDataTypeToVisibilityConverter}}" SelectedDate="{Binding Path=Value, ElementName=UserControl, Converter={StaticResource ResourceKey=DateToStringConverter}}"/>
<ComboBox Height="25" Margin="0,0,5,0" Visibility="{Binding Path=DataType, ElementName=UserControl, Converter={StaticResource ResourceKey=EnumerationDataTypeToVisibilityConverter}}" SelectedItem="{Binding Path=Value, ElementName=UserControl, Mode=TwoWay}" ItemsSource="{Binding Path=Items, ElementName=UserControl}" />
<TextBox x:Name="_txtValue" Height="25" Margin="0,0,5,0" Visibility="{Binding Path=DataType, ElementName=UserControl, Converter={StaticResource ResourceKey=NumericDataTypeToVisibilityConverter}}" Text="{Binding Path=Value, ElementName=UserControl, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged, ValidatesOnDataErrors=True, NotifyOnValidationError=True}"/>
<Image Grid.Column="2" Grid.Row="0" Source="{Binding ElementName=_txtValue, Path=(Validation.HasError), Converter={StaticResource ResourceKey=ValidationBooleanToImageConverter} }" ToolTip="{Binding ElementName=_txtValue, Path=ToolTip}" Width="16" Height="16"/>
</Grid>
...and the usercontrol reference from within the larger View is...
<control:ValueEditorControl DataType="{Binding Path=ContextualSelectedTagDataType}" Items="{Binding Path=ContextualSelectedTagItems}" Value="{Binding Path=ContextualSelectedTagDataObjectValue, Mode=TwoWay}" Height="25" VerticalAlignment="Top"/>
Can anyone point me in the right direction?

Does your VM implement INotifyPropertyChanged? Even if you implement IDataErrorInfo if WPF isn't notified of changes to the VM then it won't bind to those changes.
That being said I would change your ToolTip setter to this:
<Setter Property="ToolTip"
Value="{Binding RelativeSource={RelativeSource Self},
Path=(Validation.Errors)[0].ErrorContent}"/>
If you want the entire Style I would recommend this:
<Style TargetType="{x:Type TextBox}">
<Setter Property="Validation.ErrorTemplate">
<Setter.Value>
<ControlTemplate>
<AdornedElementPlaceholder Name="controlWithError" />
</ControlTemplate>
</Setter.Value>
</Setter>
<Style.Triggers>
<Trigger Property="Validation.HasError" Value="true">
<Setter Property="Background" Value="LightPink"/>
<Setter Property="ToolTip"
Value="{Binding RelativeSource={RelativeSource Self},
Path=(Validation.Errors)[0].ErrorContent}"/>
</Trigger>
</Style.Triggers>
</Style>