Error template not working when a ControlTemplate is applied to the window

Question

I have a simple application with App.xaml, MainWindow.xaml and a Person class. When I don't specify the template, my ValidateOnDataErrors works perfectly, putting a red border around my textbox when it is in error. However, as soon as I insert the ' Template="{StaticResource WindowTemplate}" ' in the Window tag of my MainWindow.xaml, the field is still validated but the red border disappears.

App.xaml :

<Application x:Class="WpfPOC.App"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         StartupUri="MainWindow.xaml">
<Application.Resources>
    <ControlTemplate TargetType="Window" x:Key="WindowTemplate">
        <Grid Background="{TemplateBinding Background}">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <Control x:Name="FocusCatcher"></Control>
            <TextBlock>Menu Section</TextBlock>
            <ContentPresenter Grid.Row="1" />
            <StatusBar Height="23" VerticalAlignment="Bottom" Grid.Row="2">
                <TextBlock Text="Current Editing Mode" />
            </StatusBar>
        </Grid>
    </ControlTemplate>
</Application.Resources>
</Application>

---

MainWindow.xaml :

<Window x:Class="WpfPOC.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:data="clr-namespace:WpfPOC"
    Template="{StaticResource WindowTemplate}"
    Title="MainWindow" 
    Height="350" 
    Width="525">
<Window.Resources>
    <data:Person x:Key="myDataSource" Name="Joe"/>
</Window.Resources>
<Grid>
    <TextBox Height="23" Width="120" Text="{Binding Source={StaticResource myDataSource}, Path=Name, ValidatesOnDataErrors=True}" />
</Grid>
</Window>

---

Person.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.ComponentModel;

namespace WpfPOC
{
public class Person : IDataErrorInfo
{
    public string Name { get; set; }

    #region IDataErrorInfo Members

    public string Error
    {
        get { return string.Empty; }
    }

    public string this[string columnName]
    {
        get { return "Simulated error"; }
    }

    #endregion
}
}

---

Thank you in advance for your help.

Answer 1

This happens because the default ControlTemplate used for displaying validation errors (draws a red border around the control) uses the AdornerLayer.

You have created a new ControlTemplate for the entire Window and left out the AdornerDecorator (which the default ControlTemplate for Window supplies)

So just wrap your new ControlTemplate with a AdornerDecorator like so:

<ControlTemplate TargetType="Window" x:Key="WindowTemplate">
    <AdornerDecorator>
        <Grid Background="{TemplateBinding Background}">
            <Grid.RowDefinitions>
                <RowDefinition Height="Auto" />
                <RowDefinition Height="*" />
                <RowDefinition Height="Auto" />
            </Grid.RowDefinitions>
            <Control x:Name="FocusCatcher"></Control>
            <TextBlock>Menu Section</TextBlock>
            <ContentPresenter Grid.Row="1" />
            <StatusBar Height="23" VerticalAlignment="Bottom" Grid.Row="2">
                <TextBlock Text="Current Editing Mode" />
            </StatusBar>
        </Grid>
    </AdornerDecorator>
</ControlTemplate>