Google this week released a beta version of its open source API client library for the Microsoft .NET framework. The API library supports .NET 3.5 and 4.0, and also supports Mono 2.6.7 and higher.
Mono is the open source implementation of Microsoft’s .NET framework that works on operating systems other than Microsoft Windows, and is commonly used on Linux. Versions of the API for Windows Phone 7 and Silverlight are in the works for the future.