WPF - Custom ErrorTemplate for all TextBoxes in App - wpf

Question

I have a form with many textboxes, each require the same validation Error-template.
Now, i don't wanna write these validation error-templates for every textbox. So where do i have to put that, so that all textboxes are affected?
Textbox with Validation.ErrorTemplate:
<TextBox x:Name="textBox3" TextWrapping="Wrap" Height="23" Text="{Binding User_Id, UpdateSourceTrigger=PropertyChanged, NotifyOnValidationError=True}" VerticalAlignment="Top">
<Validation.ErrorTemplate>
<ControlTemplate>
<StackPanel>
<AdornedElementPlaceholder x:Name="textBox"/>
<ItemsControl ItemsSource="{Binding}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding ErrorContent}" Foreground="Red"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</ControlTemplate>
</Validation.ErrorTemplate>
</TextBox>
My CustomControl:
public class ValidationTextBox : TextBox
{
static ValidationTextBox()
{
DefaultStyleKeyProperty.OverrideMetadata(typeof(ValidationTextBox), new FrameworkPropertyMetadata(typeof(ValidationTextBox)));
//Validation.SetErrorTemplate(new ValidationTextBox(), )
}
public ValidationTextBox() { }
}

Answer 1

You need to define new Style for TextBox inside a "Resourse" tag of textbox's container. This style will be implemented for each textbox inside container.
Example:
<StackPanel>
<StackPanel.Resources>
<Style TargetType=TextBox>
<Setter Property="Validation.ErrorTemplate">
<Setter.Value>
<ControlTemplate>
<StackPanel>
<AdornedElementPlaceholder x:Name="textBox"/>
<ItemsControl ItemsSource="{Binding}">
<ItemsControl.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding ErrorContent}" Foreground="Red"/>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
</StackPanel>
</ControlTemplate>
</Setter.Value>
</Setter>
</Style>
</StackPanel.Resources
<TextBox/>
<TextBox/>
<TextBox/>
</StackPanel>