I am using the Entity Framework code first for data access and I have a Company class which has a collection of Employees. The Employee class also has a Company property.
If you are getting this error using WebApi you can put the following in WebApiConfig.cs so json.net ignores circular refs
config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
Microsoft : Loop Reference handling in Web API