Can't get email address using Facebook SDK for asp.net

I am using Facebook SDK to get email of user. I write this code in Startup.Auth.css class :

        var x = new FacebookAuthenticationOptions();
        x.Scope.Add("email");
        x.AppId = "421656951358309";
        x.AppSecret = "5a2e5ccf163fe6918b6d6fdc8dda5184";
        x.Provider = new FacebookAuthenticationProvider()
        {
            OnAuthenticated = async context =>
            {

                context.Identity.AddClaim(new System.Security.Claims.Claim("FacebookAccessToken", context.AccessToken));
            }
        };
        x.SignInAsAuthenticationType = DefaultAuthenticationTypes.ExternalCookie;
        app.UseFacebookAuthentication(x);

And in controller, I use two method to get email but both methods fail. Here is the methods :

Method 1 : By default, after executing the first line the variable info has email property. But it always return null.

var info = await AuthenticationManager.GetExternalLoginInfoAsync();
string email = info.Email;

Method 2 : I use the following code, it also return null.

var fb = new FacebookClient(access_token.Value);
dynamic me = fb.Get("email");
string email = me.email;

Did I miss something ? or there is another method that I can use. I can get others information such as username, but for email I can't.

via Chebli Mohamed