Google+ API：如何使用 RefreshTokens 避免每次应用程序启动时都请求访问权限？

我正在尝试使用 Google+ API 来访问经过身份验证的用户的信息。我从其中一个示例中复制了一些代码，该代码运行良好（如下），但是我无法使其以跨应用程序启动重用令牌的方式运行。

我尝试捕获“RefreshToken”属性并使用provider.RefreshToken()（除其他外）并且总是得到400 Bad Request回复。

有谁知道如何进行这项工作，或者知道我在哪里可以找到一些样本？这谷歌代码网站 http://code.google.com/p/google-api-dotnet-client/wiki/APIs#Google+_API似乎没有涵盖这一点:-(

class Program
{
    private const string Scope = "https://www.googleapis.com/auth/plus.me";

    static void Main(string[] args)
    {
        var provider = new NativeApplicationClient(GoogleAuthenticationServer.Description);
        provider.ClientIdentifier = "BLAH";
        provider.ClientSecret = "BLAH";
        var auth = new OAuth2Authenticator<NativeApplicationClient>(provider, GetAuthentication);

        var plus = new PlusService(auth);
        plus.Key = "BLAH";
        var me = plus.People.Get("me").Fetch();
        Console.WriteLine(me.DisplayName);
    }

    private static IAuthorizationState GetAuthentication(NativeApplicationClient arg)
    {
        // Get the auth URL:
        IAuthorizationState state = new AuthorizationState(new[] { Scope });
        state.Callback = new Uri(NativeApplicationClient.OutOfBandCallbackUrl);
        Uri authUri = arg.RequestUserAuthorization(state);

        // Request authorization from the user (by opening a browser window):
        Process.Start(authUri.ToString());
        Console.Write("  Authorization Code: ");
        string authCode = Console.ReadLine();
        Console.WriteLine();

        // Retrieve the access token by using the authorization code:
        return arg.ProcessUserAuthorization(authCode, state);
    }
}

这是一个例子。确保添加名为 RefreshToken 的字符串设置并引用 System.Security 或找到其他方法来安全存储刷新令牌。

    private static byte[] aditionalEntropy = { 1, 2, 3, 4, 5 };

    private static IAuthorizationState GetAuthorization(NativeApplicationClient arg)
    {
        // Get the auth URL:
        IAuthorizationState state = new AuthorizationState(new[] { PlusService.Scopes.PlusMe.GetStringValue() });
        state.Callback = new Uri(NativeApplicationClient.OutOfBandCallbackUrl);

        string refreshToken = LoadRefreshToken();
        if (!String.IsNullOrWhiteSpace(refreshToken))
        {
            state.RefreshToken = refreshToken;

            if (arg.RefreshToken(state))
                return state;
        }

        Uri authUri = arg.RequestUserAuthorization(state);

        // Request authorization from the user (by opening a browser window):
        Process.Start(authUri.ToString());
        Console.Write("  Authorization Code: ");
        string authCode = Console.ReadLine();
        Console.WriteLine();

        // Retrieve the access token by using the authorization code:
        var result = arg.ProcessUserAuthorization(authCode, state);

        StoreRefreshToken(state);
        return result;
    }

    private static string LoadRefreshToken()
    {
        return Encoding.Unicode.GetString(ProtectedData.Unprotect(Convert.FromBase64String(Properties.Settings.Default.RefreshToken), aditionalEntropy, DataProtectionScope.CurrentUser));
    }

    private static void StoreRefreshToken(IAuthorizationState state)
    {
        Properties.Settings.Default.RefreshToken = Convert.ToBase64String(ProtectedData.Protect(Encoding.Unicode.GetBytes(state.RefreshToken), aditionalEntropy, DataProtectionScope.CurrentUser));
        Properties.Settings.Default.Save();
    }