Upon browsing the source code for WPF I stumbled across a few dependency properties that use certain FrameworkPropertyMetadataOptions in their definitions. I am creating a custom window control with its own template design. One of the dependency properties I am creating is to set the background color of the title bar:
public static readonly DependencyProperty TitleBarBackgroundProperty =
DependencyProperty.Register(
"TitleBarBackground",
typeof(Brush),
_typeofThis,
new FrameworkPropertyMetadata(
null,
FrameworkPropertyMetadataOptions.AffectsRender |
FrameworkPropertyMetadataOptions.SubPropertiesDoNotAffectRender));
I'm trying to understand if FrameworkPropertyMetadataOptions.SubPropertiesDoNotAffectRender is good to have for my property. I am setting these two flags because this is how a Panel's background dependency property is defined here.
I found the following article on Microsoft's learn: https://learn.microsoft.com/en-us/dotnet/api/system.windows.frameworkpropertymetadataoptions?view=windowsdesktop-7.0
My question is what qualifies as a "sub-property" and do I need it for my property I am defining if all I'm doing with it is binding it to a Grid's background property (which I assume already has these flags since it inherits the panel's background property). Any help would be greatly appreciated, thank you.
If the property only serves as source property of a Binding there is no need to set any property metadata at all. If re-rendering is required, the target object of the Binding should initiate it.
The declaration of the dependency property identifier field should simply look like this:
public static readonly DependencyProperty TitleBarBackgroundProperty =
DependencyProperty.Register(
nameof(TitleBarBackground),
typeof(Brush),
typeof(YourControl));