The Silverlight/WPF testing framework find methods strictly respect the XAML tag as type. There is no API method such that one can find an element providing a base type. Consider the custom control templates so applicable in XAML. For example:

Find.ByType<ButtonBase>() will only return an element if it has the "ButtonBase" tag, which is a useless case. If one needs to find whatever button is there she needs to understand the exact button type to search by.