Function call within XAML code?

Question

I'd like to set a style on all my TextBox controls that does the following when it receives keyboard focus:

1) Change the background color
2) Call .SelectAll() to highlight all text

I have this so far:

<Style TargetType="TextBox">
<Style.Triggers>
            <Trigger Property="IsKeyboardFocusWithin" Value="True">
                <Setter Property="Background">
                    <Setter.Value>
                        <SolidColorBrush Color="#FFFFD1D9"/>
                    </Setter.Value>
                </Setter>
           </Trigger>
</Style.Triggers>
</Style>

Is there a way to also call .SelectAll() ? Thanks.

Solution

You can do this using attached behaviours.

Example

public static class TextBoxBehaviour
{
    public static bool GetSelectAll(TextBoxBase target)
    {
        return (bool)target.GetValue(SelectAllAttachedProperty);
    }

    public static void SetSelectAll(TextBoxBase target, bool value)
    {
        target.SetValue(SelectAllAttachedProperty, value);
    }

    public static readonly DependencyProperty SelectAllAttachedProperty = DependencyProperty.RegisterAttached("SelectAll", typeof(bool), typeof(TextBoxBehaviour), new UIPropertyMetadata(false, OnSelectAllAttachedPropertyChanged));

    static void OnSelectAllAttachedPropertyChanged(DependencyObject o, DependencyPropertyChangedEventArgs e)
    {
        ((TextBoxBase)o).SelectAll();
    }
}

Usage

<Style TargetType="{x:Type TextBox}" xmlns:behaviours="clr-namespace:Controls.Behaviours">
  <Style.Triggers>
      <Trigger Property="IsKeyboardFocusWithin" Value="True">
          <Setter Property="Background" Value="#FFFFD1D9"/>
          <Setter Property="behaviours:TextBoxBehaviour.SelectAll" Value="True"/>
     </Trigger>
  </Style.Triggers>
</Style>

References

• Josh Smith on Attached Behaviours

NB: Wasn't able to test the above implementation, in theory though it should just work™.

HTH,

Comments

[Ray Burns]

+1 Excellent answer. Almost exactly what I would have written. Personally I would change the body of the method to simply ((TextBoxBase)target).SelectAll() so as to throw an intelligible exception if the property is used erroneously. From a QA perspective this is better in the long run than silently ignoring such errors: You catch your bugs up front rather than having them lurk hidden for years.

[Dennis]

@Ray Burns: I agree. It is a bad habit that I am trying to move away from. I have edited my answer.

[BCA]

Thanks for that--it worked perfectly. FYI, for anyone who wishes to implement this for a PasswordBox: implement a separate PasswordBoxBehaviour class and replace all occurrences of TextBoxBase with PasswordBox.