WPF button to update a textbox in xaml with validator - wpf

Question

How can I get a button to reset text in a textbox to a known value? In my example the validation rule is triggered so I can't use the button command to update the property, which is good because I don't want the property set if it's not valid. I just want the button to basically reset the value in xaml without involving the property. How would I do that?
<TextBox Grid.Column="1" Grid.Row="9" HorizontalAlignment="Left" Height="20" Width="105" Name="Elevation"
Validation.ErrorTemplate="{StaticResource validationTemplate1}" Style="{StaticResource textBoxInError}">
<TextBox.Text >
<Binding Path="Elevation" Mode="TwoWay" UpdateSourceTrigger="LostFocus">
<Binding.ValidationRules>
<rules:NotEmptyValidationRule ValidatesOnTargetUpdated="True" ValidationStep="RawProposedValue"/>
<rules:DoubleValidationRule ValidatesOnTargetUpdated="True" ValidationStep="RawProposedValue"/>
</Binding.ValidationRules>
</Binding>
</TextBox.Text>
</TextBox>
<Button Grid.Column="2" Grid.Row="9" Height="20" Command="{Binding ClickResetCommand}" CommandParameter="Elevation" >R</Button>
Still looking for a XAML solution but for now I've change the button to use OnClick and in the code behind using the following...
case "Elevation":
Elevation.Text = "50";
Validation.ClearInvalid(Elevation.GetBindingExpression(TextBox.TextProperty) ?? throw new InvalidOperationException());
Elevation.Focus();
break;