How can I turn off default validation in WPF? - wpf

Question

It seems that WPF has some validation rule which is turned on by default. When I enter non numeric text into the bound textbox and tab out it, a read border shows around it. What is going on here? I Have set ValidatesOnExceptions to false, where is the validation rule coming from? I am using version 4.5.2 of the .Net framework.
Here is my XAML
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:local="clr-namespace:WpfApplication2"
mc:Ignorable="d"
Title="MainWindow" Height="159.206" Width="193.953">
<Grid>
<TextBox x:Name="textBox" Height="23" HorizontalAlignment="Left" VerticalAlignment="Top" TextWrapping="Wrap"
Text="{Binding Foo, ValidatesOnExceptions=False, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}"
Width="91" Margin="10,10,0,0"/>
<TextBox x:Name="textBox1" HorizontalAlignment="Left" Height="23" Margin="10,48,0,0"
TextWrapping="Wrap" Text="TextBox" VerticalAlignment="Top" Width="91"/>
</Grid>
</Window>
Here is the code behind
namespace WpfApplication2
{
public partial class MainWindow : Window
{
public int Foo { get; set; } = 42;
public MainWindow()
{
InitializeComponent();
}
}
}

Answer 1

You can never set an int property to anything else than a valid int value.
This "validation", or rather type-safety feature of the programming language, cannot be turned off.
You can however get rid of or customize the the default error template if you want to. Just set the Validation.ErrorTemplate property to an emoty ControlTemplate:
<TextBox x:Name="textBox" Height="23" HorizontalAlignment="Left" VerticalAlignment="Top" TextWrapping="Wrap"
Text="{Binding Foo, ValidatesOnExceptions=False, RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type Window}}}"
Width="91" Margin="10,10,0,0">
<Validation.ErrorTemplate>
<ControlTemplate />
</Validation.ErrorTemplate>
</TextBox>

Answer 2

On app startup, you can add this call to FrameworkCompatibiltyPreferences to disable all textboxes from messing with your input:
class App
{
[STAThread]
public static void Main(params string[] args)
{　　　　
System.Windows.FrameworkCompatibilityPreferences.KeepTextBoxDisplaySynchronizedWithTextProperty = false;
Application app = new Application();
app.Run(new Window1());
}
}
If you're using data binding, it appears that the textboxes will still protect against invalid input. A validation error will be shown (default being the red border) and the view model property will not be set with the invalid value. But now you can input whatever string you want. Makes entering decimal values bound to float or double properties MUCH easier.