Question

I’ve looked but apparently can’t get the syntax correct when correlating to classes and styles. I have controls that have certain behavior. Some I derive to add additional behavior. Now, I want a style to correspond to each version. In its simplest example, I will ignore those classes as I know style is specifically associated to visual and not function impact. Some previous questions were close, but I am still missing something.

public class MyLabel : Label
{}

public class MyLabel2 : MyLabel
{}

So from the above, I should be able to have 3 styles in my resource dictionary. One for the generic “Label”, one for instances where I have a control that is derived from “MyLabel”, and another for “MyLabel2”. The “local:” points to my class library per the “Theme” xaml declaration.

<Style x:Key="baseLabel" TargetType="Label">
   <Setter Property="FontSize" Value="10" />
</Style>

<Style x:Key="styleMyLabel" TargetType="local:MyLabel"  BasedOn="{StaticResource baseLabel}" >
   <Setter Property="FontSize" Value="14" />
</Style>

<Style x:Key="styleMyLabel2" TargetType="{x:Type local:MyLabel2}" BasedOn="{StaticResource styleMyLabel}" >
   <Setter Property="FontSize" Value="22" />
</Style>

Again, for very simplistic purposes, just using a simple label for inheritance following purposes. In my window xaml file. Per the window xaml, the “src:” points to my class library, which is the same library as “local:” referenced in the theme (but I tried both ways… to have both instances refer to the xmlns:local in both, but it didn’t appear to make a difference).

<src:MyLabel Content="Does Not Respect Style even though derived from MyLabel class" />
<src:MyLabel Content="This one works " Style="{DynamicResource styleMyLabel}" />

<src:MyLabel2 Content="This one doesnt work"/>
<src:MyLabel2 Content="This one works " Style="{DynamicResource styleMyLabel2}" />

I’m thinking I shouldn’t have to explicitly identify the style if its derived from a class that has a style of the corresponding Target Type. Hopefully its something stupid simple but I can’t get my head wrapped around it…

Answer 1

Ok, I’ve stumbled into what APPEARS to be working as the answer, but don’t understand why… If I try to change the style for the MyLabel2 (which is the second derived instance) from

<Style x:Key="styleMyLabel2" TargetType="{x:Type local:MyLabel2}" BasedOn="{StaticResource styleMyLabel}" >
   <Setter Property="FontSize" Value="22" />
</Style>

to (just removing the x:Key element)

<Style TargetType="{x:Type local:MyLabel2}" BasedOn="{StaticResource styleMyLabel}" >
   <Setter Property="FontSize" Value="22" />
</Style>

the XAML works… WITHOUT having to explicitly associate the “Style” to be used. It finds it based on the class association directly.

<src:MyLabel2 Content="Now Works as expected"/>

Now that it works, can someone maybe explain why the extra use of the x:Key reference kills it? ie: if you have the x:key, its not implied by the class instance, but not having it, the direct class DOES find it automatically.

EXPANDED FROM MY PLAYING AROUND WITH STYLES…

So, here is some extras that I’ve found out. A style can be defined more than once to the same TARGET TYPE… However, one can have an x:key reference, and another a BasedOn reference. This APPEARS to be like overloading a function with same number, but different data type parameters.

In my problem, as soon as the “x:Key” reference was added to the style, any direct class instances of the “TargetType” were NOT automatically linked up to the proper style, almost like the style declaration with the “x:key” REQUIRES any instances of a class to explicitly add the style context within the xaml of the control. So now, how to have it BOTH ways. I created a SECOND style with the TargetType as the baseclass, but had ITs BasedOn pointing to the x:key referenced one. This way, I get the default customization of the style, yet can STILL assign it to the baseclass and the derived class as well, so all 3 versions of a control can be automatically synchronized with the corresponding Style without EXPLICIT referencing.

<Style TargetType="Label" x:Key="wpfBaseLabel">
   <Setter Property="FontSize" Value="11" />
</Style>

<Style TargetType="Label" BasedOn="{StaticResource wpfBaseLabel}" />

<Style TargetType="{x:Type local:MyLabel}" BasedOn="{StaticResource wpfBaseLabel}">
   <Setter Property="Foreground" Value="Blue" />
</Style>

So, now, within the final XAML, I can have all 3 “classes” used with or without explicit style association.