WPF Concatenated DataTrigger Binding - wpf

Question

In my application i'd like to change the Background property of a TextBox when the <Property>IsChanged property of my Model is set to True
I have been able to successfully do this for one of my TextBox controls with the following style:
Notice the hard-coded binding for FirstNameIsChanged in the DataTrigger
<TextBox.Style>
<Style TargetType="TextBox" BasedOn="{StaticResource {x:Type TextBox}}">
<Style.Triggers>
<DataTrigger Binding="{Binding FirstNameIsChanged}" Value="True">
<Setter Property="Background" Value="SteelBlue"/>
</DataTrigger>
</Style.Triggers>
</Style>
</TextBox.Style>
If my application has a form with 10 or so TextBox controls (FirstName, MiddleName, LastName, Age, Gender etc.) i don't want to copy and paste the above code if i'm only changing the Binding on the DataTrigger for each property.
I've researched using MultiBinding in combination with RelativeSource and StringFormat. I'm trying to create a binding that gets the Tag property of the TextBox and adds "IsChanged" to the name but i have not managed to get it working (I don't see any binding warnings/errors in Visual Studio either)
This is the Style i'm trying to create:
<Style x:Key="TextBoxTestStyle" TargetType="TextBox" BasedOn="{StaticResource {x:Type TextBox}}">
<Style.Triggers>
<DataTrigger Value="True">
<DataTrigger.Binding>
<MultiBinding StringFormat="\{0\}IsChanged">
<Binding Path="Tag"
RelativeSource="{RelativeSource Mode=FindAncestor, AncestorType={x:Type TextBox}}" />
</MultiBinding>
</DataTrigger.Binding>
<Setter Property="Background" Value="Red"/>
</DataTrigger>
</Style.Triggers>
</Style>
Each of the Properties on my Model have their own IsChanged property that i'm using for Change Tracking, this is a quick preview of my Model and how i've made the IsChanged properties:
public class Person
{
public string FirstName { get; set; }
public bool FirstNameIsChanged { get; set; }
public string MiddleName { get; set; }
public bool MiddleNameIsChanged { get; set; }
public string LastName { get; set; }
public bool LastNameIsChanged { get; set; }
public int Age { get; set; }
public bool AgeIsChanged { get; set; }
public DateTime? DateOfBirth { get; set; }
public bool DateOfBirthIsChanged { get; set; }
}
As an example, if i have the following TextBox and i set the Tag property to "FirstName", the style should set the Background property to "Red" if the FirstNameIsChanged property is set to True :
<TextBox x:Name="FirstNameTextBox"
Tag="FirstName"
Margin="3"
Height="23"
HorizontalAlignment="Stretch"
VerticalAlignment="Center"
Style="{DynamicResource TextBoxTestStyle}"
Text="{Binding FirstName,
Mode=TwoWay,
NotifyOnValidationError=true,
ValidatesOnExceptions=true,
UpdateSourceTrigger=PropertyChanged}"/>
The style (If it's codable) would allow me to set the Tag property on 10 TextBox controls but only have 1 style for all my TextBox controls instead of having to copy and paste the style 10 times. I also want to avoid adding "Boiler plate" code if i decide to add additional properties to my Model in the future such as an IsValid property or an IsEnabled property.
Some ideas i've had:
Can i add "IsChanged" to the string value of the Tag property and use the resulting string in a binding? e.g. Tag("FirstName") + "IsChanged" = "FirstNameIsChanged"
From a Style can i walk up the visual tree and grab the Binding that is already on the Text property and add "IsChanged" to the path? e.g. BindingPath("FirstName") + "IsChanged" = "FirstNameIsChanged"

Answer 1

You shouldn't be comparing to a boolean. Also, to make it Generic, I would make the Tag TextBox-independent, e.g. IsChanged:
<Style x:Key="TextBoxTestStyle" TargetType="TextBox">
<Style.Triggers>
<Trigger Property="Tag" Value="IsChanged">
<Setter Property="Background" Value="Red"/>
</Trigger>
</Style.Triggers>
</Style>
EDIT
To preserve to Booleans you could use a less generic solution. Since Tag expects a string I added a Converter (you could also create another Dependeny Property expecting a boolean).
<....Resources>
<local:BoolToStringConverter x:Key="BoolToStringConverter"/>
<Style x:Key="TextBoxStyle" TargetType="TextBox">
<Style.Triggers>
<Trigger Property="Tag" Value="True">
<Setter Property="Background" Value="Red"/>
</Trigger>
</Style.Triggers>
</Style>
</....Resources>
...
<TextBox
x:Name="FirstNameTextBox"
Tag="{Binding FirstNameIsChanged,
Converter={StaticResource BoolToStringConverter}}"
Style="{StaticResource TextBoxStyle}"
...
/>
<TextBox
x:Name="MiddleNameTextBox"
Tag="{Binding MiddleNameIsChanged,
Converter={StaticResource BoolToStringConverter}}"
Style="{StaticResource TextBoxStyle}"
...
/>
...
Without reaching for code-behind (see my comment), this is probably the shortest solution. If you're not using the TextBox Tag Property for anything else, you could also make the Style implicit.