The following exception is thrown when changing the value of specific properties.
InvalidCastException: 'Object must implement IConvertible.'

This happens if the bound property is of a base type and the provided value is of a type that inherits the base type. For example, if you bind to a property of type Brush and you assign a value of type SolidColorBrush.

When a PropertyDefinition with binding to an attached property is added to the PropertyDefinitions collection, the created editor is not bound correctly. 

Add an event that is raised when the editor's value gets updated and just before the value is updated back to the associated data item when PropertySetMode is Union or Intersection.

Currently, you can use the PropertySetsValidationFunction to intercept this moment, but the function is not invoked only for the currently edited property, but for all other properties in the PropertyGrid and you cannot indicate which one triggered the change.

When the Expression_Dark theme is applied to the RadPropertyGrid, selecting an item is hard to read, as the item's foreground is white and the selection state is in a similar color.

To work this around, use the following Style:

 

Add a Visibility DependencyProperty (to support data binding) to the GroupDefinition class. The same setting is available in the PropertyDefinition objects and it affects the property fields in the UI. The Visibility of the GroupDefinitions should hide/show the entire group along with all its child property fields.

The GroupDefinition Visibility should not update the Visibility of the child PropertyDefinition objects. Both properties should work independent.

Add a property on the PropertyDefinition or the PropertyGridField object that changes the visibility of the expand/collapse button that is displayed when you have nested properties. The developer should be able to manually define if the button should be visible or not.

Currently, the order of the GroupDefinitions will be based on the OrderIndex of the PropertyDefinitions, which means that in order to reorder the groups, you will have to order the PropertyDefinitions.

The GroupDefinition class exposes the DisplayIndex property, which we can review and improve its functionality to allow the user to directly order the groups based on it.