使用Facebook c#sdk:

using Facebook c# sdk:

 string signedRequest = Request.Form["signed_request"];
     var DecodedSignedRequest = FacebookSignedRequest.Parse(Facebook.Web.FacebookWebContext.Current.Settings.AppSecret, signedRequest);
                    dynamic SignedRequestData = DecodedSignedRequest.Data;
         accessToken = (String)SignedRequestData.oauth_token;
                        var app = new FacebookWebClient();
                        var me = (IDictionary<string, object>)app.Get("me");
                        firstName = (string)me["name"];
                        U_Id = (string)me["id"];