I have a brush that is part of a ResourceDictionary that is merged to Application.Resources.

But for some reason it's not resolved at runtime when a style is being applied to one of the controls. However, if I call Application.Current.FindResource("BrushName") from the Immediate Window at the time when exception is thrown, the resource is found.

Am I missing something? Isn't WPF supposed to try to look for the resource in the app's resources?

UPDATE The application is quite big, so I can't post all actual code but here's the way the resources are merged and used:

Brushes.xaml

<ResourceDictionary ...>
  <SolidColorBrush x:Key="BrushName" Color="#12345678" />
<\ResourceDictionary>

SomeStyles.xaml

<ResourceDictionary ...>
  <Style x:Key="SomeStyle">
    <Setter Property="SomeProperty" Value="{StaticResource BrushName}" />
  </Style>
</ResourceDictionary>

App.xaml

<Application ...>
  <Application.Resources>

    <ResourceDictionary>
      <ResourceDictionary.MergedDictionaries>
        <ResourceDictionary Source="Brushes.xaml" />
        <ResourceDictionary Source="SomeStyles.xaml" />
      </ResourceDictionary.MergedDictionaries>
    </ResourceDictionary>


  </Application.Resources>
</Application ...>

And then some control might use the style using the resource like this:

...
Style={StaticResource SomeStyle}
...