SharpKML is an implementation of the Open Geospatial Consortium (OGC) KML 2.2 standard developed in C#, able to read/write both KML files and KMZ files.
The library has been based on Google's C{"++"} implementation of the standard (libkml), however, instead of using the SWIG bindings the code has been written from scratch to give a more C# feel, by using properties, extension methods and the built in Xml handling of the .NET framework.
The easiest way to use the library is to install the SharpKml.Core NuGet package, however, you can also download the binaries/source code from this project page.
The main library for handling KML data targets the Portable Class Libraries, so is compatible with .NET Framework 4 and higher, Silverlight 5, Windows Phone 8, Windows Store apps (Windows 8) and higher.
If you need to support KMZ compressed archives then there is a separate library which targets the .NET 4 Framework. This library has a dependency on DotNetZip for the handling of ZIP archives; the download for the KMZ part bundles the core library, the KMZ library and the DotNetZip (reduced) binaries.