Question

I make a textbox. It is highlighted when it is focused. User inputs text in TextBox and code tests what users enter. If input data is not correct then I want this TextBox be handled by BlurEffect(It wtites in XAML):

<Setter Property="Effect">
      <Setter.Value>
      <BlurEffect Opacity="1" Color="Red" BlurRadius="30"/>
 </Setter.Value>

This code catches if input data is not correct:

    private void Filter_textBox_KeyUp(object sender, KeyEventArgs e)
    {
        string str=Filter_textBox.Text;
        if (str == "bbb")
        {
            Filter_textBox.BitmapEffect = null;
            Filter_textBox.Foreground = Brushes.Black;
        }
        else
             //<BlurEffect Opacity="1" Color="Red" BlurRadius="30"/>

And I want to trigger “BlutEffect” in case of “else”.
How to do it? Is it real?

Answer 1

    private void Filter_textBox_KeyUp(object sender, KeyEventArgs e)
    {
        string str = Filter_textBox.Text;
        if (str == "bbb")
        {
            Filter_textBox.Effect = null;
            Filter_textBox.Foreground = Brushes.Black;
        }
        else
        {
            DropShadowEffect effect = new DropShadowEffect();
            effect.Opacity = 1;
            effect.Color = Colors.Red;
            effect.BlurRadius = 30;
            Filter_textBox.Effect = effect;
        }
    }

This does exactly what you’re trying to do. But this is not a good practice. You can achieve the same result by using a DataTrigger.