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:

<Style TargetType="telerik:PropertyGridField">
    <Style.Triggers>
        <Trigger Property="IsSelected" Value="True">
            <Setter Property="Foreground" Value="Black"/>
        </Trigger>
    </Style.Triggers>
</Style>

 Add selected inactive state for PropertyGrid Field.

When a RadPropertyGrid instance is placed inside a RadBusyIndicator, the StyleManager cannot apply the styles correctly and it causes an InvalidOperationException at runtime.

Workaround: Use the NoXaml version of the assemblies with the needed themes.

An non edit mode is enabled in the control when the EditMode is set to Single. In this case, only one field can enter edit mode and the rest are read only. 

Currently, there is no API that allows you to customize the content (that shows the property value) of the read only fields.

Add an API that allows you to customize the read only content. Similar to the EditorTemplate of the PropertyDefinition.