The StringWithQualityHeaderValue class provides support for strings with a quality factor used in some headers as defined in RFC 2616 by the IETF.
Quality factors allow the user agent to indicate the relative degree of preference for various options in various headers including the Accept, Accept-Charset, Accept-Encoding, and Accept-Language headers. Quality uses a scale from 0 to 1. The default value is q=1.
Windows Phone 8.1, Windows Phone 8, 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)