facebook long-live access using DotNetOpenAuth - facebook

Question

i am creating an application in asp.net, which will use the user's facebook data using its api's,
but in order to access the Fb api's we need to perform the OAuth(2.0) first.
i did that too by using the DotNetOpenAuth library in the following code:
private static readonly FacebookClient client = new FacebookClient
{
ClientIdentifier = ConfigurationManager.AppSettings["fbAppID"],
ClientCredentialApplicator = ClientCredentialApplicator.PostParameter(ConfigurationManager.AppSettings["fbSecret"]),
};
protected void Page_Load(object sender, EventArgs e)
{
IAuthorizationState authorization = client.ProcessUserAuthorization();
if (authorization == null)
{
// Kick off authorization request
client.RequestUserAuthorization();
}
else
{
var req = WebRequest.Create("https://graph.facebook.com/oauth/access_token?client_id=" + ConfigurationManager.AppSettings["facebookAppID"] + "&client_secret=" + ConfigurationManager.AppSettings["facebookAppSecret"] + "&grant_type=fb_exchange_token&fb_exchange_token=" + Uri.EscapeDataString(authorization.AccessToken));
var request = WebRequest.Create("https://graph.facebook.com/me?access_token=" + Uri.EscapeDataString(authorization.AccessToken));
using (var response = request.GetResponse())
{
using (var responseStream = response.GetResponseStream())
{
var graph = FacebookGraph.Deserialize(responseStream);
this.nameLabel.Text = HttpUtility.HtmlEncode(graph.Name);
}
}
}
}
my question here is, how can i get the long-lived access token of facebook using the DotNetOpenAuth library, so that user do not need to login again and again and i can store that somewhere.
please help me.

Answer 1

If possible use Facebook SDK for .Net to create access token for long time. may be 60 days.
using Facebook;
var cl = new FacebookClient(short_lived_access_token);
dynamic result = client.Post("oauth/access_token", new
{
client_id = "your app id",
client_secret = "your app secret",
grant_type = "fb_exchange_token",
fb_exchange_token = client.AccessToken
});
var long_lived_access_token = result.access_token;