/// <summary>
/// Generates a MD5 signature for the facebook session.
/// </summary>
/// <param name="secret">
/// The app secret.
/// </param>
/// <param name="dictionary">
/// The dictionary.
/// </param>
/// <returns>
/// Returns the generated signature.
/// </returns>
/// <remarks>
/// http://developers.facebook.com/docs/authentication/
/// </remarks>
internal static string GenerateSessionSignature(string secret, IDictionary <string, object> dictionary)
{
Contract.Requires(!string.IsNullOrEmpty(secret));
Contract.Requires(dictionary != null);
Contract.Ensures(!string.IsNullOrEmpty(Contract.Result <string>()));
var payload = new StringBuilder();
// sort by the key and remove "sig" if present
var parts = (from a in dictionary
orderby a.Key
where a.Key != "sig"
select string.Format(CultureInfo.InvariantCulture, "{0}={1}", a.Key, a.Value)).ToList();
parts.ForEach(s => payload.Append(s));
payload.Append(secret);
var hash = FacebookUtils.ComputerMd5Hash(Encoding.UTF8.GetBytes(payload.ToString()));
var signature = new StringBuilder();
foreach (var h in hash)
{
signature.Append(h.ToString("x2", CultureInfo.InvariantCulture));
}
return(signature.ToString());
}
