How to specify using the default style in XAML?

Question

The basic problem is that a WPF application I'm working on makes extensive use of Material Design. The problem I'm running into is that it appears that the DatePicker style makes it very difficult to apply a converter to get its output to look like "01/23/2020" instead of "01-23-2020". I can do this in a non-Material Designs environment but the exact same code refuses to call the converter that reformats the DateTime string to the format I want. To test this hypothesis I thought that I'd use a standard DatePicker instead of the Mater Designs restyled version but I'm having trouble figuring out how to tell XAML to not use Material Design's restyled DatePicker. How can that be done?

Answer 1

Set x:null as the style to be the default style.

If you are using MaterialDesignThemes, you can overwrite the resource for the key named 'MaterialDesignDatePickerTextBox'.

<StackPanel>
    <StackPanel.Resources>
        <ResourceDictionary Source="pack://application:,,,/MaterialDesignThemes.Wpf;component/Themes/MaterialDesignTheme.Defaults.xaml" />
    </StackPanel.Resources>

    <Border  Margin="10">

        <DatePicker Style="{x:Null}"><!-- Clear Style -->
            <DatePicker.Resources>
                <Style TargetType="{x:Type DatePickerTextBox}">
                    <Setter Property="Text" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=DatePicker},Path=SelectedDate,StringFormat=dd/MM/yyyy}" />
                </Style>
            </DatePicker.Resources>
        </DatePicker>
    </Border>


    <Border BorderBrush="Black" BorderThickness="1" Margin="10">
        <DatePicker >
            <DatePicker.Resources>

                <!-- Inherit style of MaterialDesign -->
                <Style TargetType="{x:Type DatePickerTextBox}" 
                        x:Key="MaterialDesignDatePickerTextBox" 
                        BasedOn="{StaticResource MaterialDesignDatePickerTextBox}">
                    <Setter Property="Text" Value="{Binding RelativeSource={RelativeSource Mode=FindAncestor,AncestorType=DatePicker},Path=SelectedDate,StringFormat=dd/MM/yyyy}" />
                </Style>

            </DatePicker.Resources>
        </DatePicker>
    </Border>
</StackPanel>