get-current-blog.cs

var urls = Telligent.Evolution.Extensibility.Api.Version1.PublicApi.Url;
var blogs = Telligent.Evolution.Extensibility.Api.Version1.PublicApi.Blogs;

var context = urls.CurrentContext;

var blogInfo = context.ContextItems.Find(item => item.ContentTypeId == blogs.ContentTypeId);

if (blogInfo == null || !blogInfo.ContentId.HasValue)
{
  // No current blog - do something
  throw new Exception();
}

var blog = blogs.Get(blogInfo.ContentId);