Changing opacity from code-behind

Question

Why has the following event in a Window code-behind no effect? ``` void about_Click(object sender, RoutedEventArgs e) { // TopLevel.Opacity = 1.0, Splashscreen.Opacity = 0.0 TopLevel.Opacity = 0.1; // still: TopLevel.Opacity = 1.0 Splashscreen.Opacity = 1.0; // still: Splashscreen.Opacity = 0.0 } ``` The opacity values do not change. I discovered that the following Trigger is the cause of my issue: ``` ``` When I remove it the code-behind is working. For completeness, this is the animation: ```

Accepted Answer

Again you and again the same issue with dependency property value precedence.

Take a look at the priorities.

Property system coercion.

Active animations, or animations with a Hold behavior. In order to have any practical effect, an animation of a property must be able to have precedence over the base (unanimated) value, even if that value was set locally.

Local value. A local value might be set through the convenience of the "wrapper" property, which also equates to setting as an attribute or property element in XAML, or by a call to the SetValue API using a property of a specific instance.

In your case animation takes over.

Your code here is #3. You are setting the local value but animation still takes over.

```
void about_Click(object sender, RoutedEventArgs e)
{
   // TopLevel.Opacity = 1.0, Splashscreen.Opacity = 0.0
   TopLevel.Opacity = 0.1;
   // still: TopLevel.Opacity = 1.0
   Splashscreen.Opacity = 1.0;
   // still: Splashscreen.Opacity = 0.0
}
```

I hope now you finally understand how priorities work. :) :) :)

Changing opacity from code-behind

Solution

Problem