DependencyProperty.OverrideMetadata Method (Type, PropertyMetadata)
Specifies alternate metadata for this dependency property when it is present on instances of a specified type, overriding the metadata that existed for the dependency property as it was inherited from base types.
Assembly: WindowsBase (in WindowsBase.dll)
Dependency property metadata should be overridden before the property system uses the dependency property. This equates to the time that specific instances are created using the class that registers the dependency property. Calls to OverrideMetadata should only be performed within the static constructors of the type that provides itself as the forType parameter of this method, or through similar instantiation. Attempting to change metadata after instances of the owner type exist will not raise exceptions, but will result in inconsistent behaviors in the property system.
After metadata for a particular derived class override is established with this method, subsequent attempts to override metadata on this same derived class will raise an exception.
The supplied metadata is merged with the property metadata for the dependency property as it exists on the base owner. Any characteristics that were specified in the original base metadata will persist; only those characteristics that were specifically changed in the new metadata will override the characteristics of the base metadata. Some characteristics such as DefaultValue are replaced if specified in the new metadata. Others, such as PropertyChangedCallback, are combined. Ultimately, the merge behavior depends on the property metadata type being used for the override, so the behavior described here is for the existing property metadata classes used by WPF dependency properties. For details, see Dependency Property Metadata and Framework Property Metadata.