ElasticLINQ is a free C# library for searching Elasticsearch using LINQ syntax in .NET, e.g.
var db = new ElasticContext(new ElasticConnection(new Uri("http://myserver:9200")));
var p = db.Query<People>().Where(p => p.Tags.Contains("tech") && p.State == "WA");
ElasticLINQ supports .NET 4.5 & PCL with Elasticsearch 0.9.0 through Elasticsearch 1.7.
Elasticsearch 2.0 is not yet supported or tested. Some queries may work although GroupBy will definitely fail.
Binary releases are available via NuGet. For information on getting started, see the Wiki.