How to specify BasedOn tag in a style to a style defined in some other file.
Example,
Dictionary1.xaml defines
<Style x:Key="basicStyle" TargetType="TextBlock" >
<Setter Property="FontSize" Value="24"></Setter>
<Setter Property="Foreground" Value="DarkGray"></Setter>
<Setter Property="FontWeight" Value="Bold"></Setter>
</Style>
In Dictionary2.xaml i need something like
<Style x:Key="headerStyle" TargetType="TextBlock" >
<Setter Property="FontSize" Value="46"></Setter>
<Setter Property="Foreground" Value="DarkGray"></Setter>
<Setter Property="FontWeight" Value="Bold"></Setter>
</Style>
How to achieve this?
The easy way:
In Dictionary2.xaml
define MergedDictionaries (right after the opening ResourceDictionary
tag):
<ResourceDictionary.MergedDictionaries>
<ResourceDictionary Source="/Path/to/Dictionary1.xaml" />
</ResourceDictionary.MergedDictionaries>
And then
<Style x:Key="headerStyle" TargetType="TextBlock" BasedOn="{StaticResource basicStyle}" >
.....
</Style>
This will solve the issue, but as with all easy solutions there's a catch: each time you merge dictionaries you effectively create a copy of the merged dictionary. And it's recursive - if you have Dict3.xaml and Dict4.xaml that both load Dictionary2.xaml, you will have three instances of Dictionary1.xaml created. With a complex dependency structure you can get to a point that you have 19,000+ dictionary objects in memory at application start up and the memory footprint goes from 180MB to 1200MB (TrueStory™ :( ).
The solution is a SharedResourceDictionary. The implementation in the tutorial should be seen as a starting point and will probably need some level of tweaking - depending on use scenario. Google "wpf SharedResourceDictionary" for some gotchas and solutions.