Описание тега csquery
CsQuery is a complete CSS selector engine, HTML parser, and jQuery port for C# and .NET 4+
CsQuery is a jQuery port for.NET 4. It implements all CSS2 & CSS3 selectors, all the DOM manipulation methods of jQuery, and some of the utility methods. The majority of the jQuery test suite (as of 1.6.2) has been ported to C#. Here is its official github.