Typically, Source is specified as a Pack URI, which references the location of a resource dictionary that is included as a noncompiled Resource or Content build action by your application building project. For details on the Pack URI format, see Pack URIs in WPF.
Generally, the Source property is set only for a ResourceDictionary that is specified for the MergedDictionaries property (either as a property element in XAML, or as a ResourceDictionary item of the collection in code). In this context, setting the value for Source will merge the dictionary contents found at the supplied URI into the current ResourceDictionary. Any load failures will cause an exception to be thrown.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)