Question

我在.net中使用FB SDK，在我的网站上有多个由用户配置的Facebook电子邮件。每当用户想要在FB上发布任何消息时，他都可以选择任何电子邮件，并且应该能够登录FB。

问题是，如果用户已经登录到FB但想要在其他某个FB帐户上发布消息，我们无法向他显示登录屏幕，并且消息会在已登录的帐户中发布。

即使我们有用户auth_type=reauthenticate，但这也无助于每次都显示登录屏幕。我需要一个类似Twitter的机制来强制登录FB。

有人可以提供帮助吗？

Answer 1

Facebook应用程序 - 记下您的App ID和App Secret
Json.NET安装在你的Bin中。在此下载：http://json.codeplex.com
以下参考文献需要添加到您的应用设置页面中：

使用Newtonsoft.Json.Linq; 使用Newtonsoft.Json.Serialization; 使用System.Collections.Generic; 使用System.Security.Cryptography;

这是HTML内容：

 <div id="fb-root"></div>

function runLogin() {
FB.init({
appId  : 'ENTERYOURAPPIDHERE',
status : true,
cookie : true,
xfbml  : true,
channelURL: 'ENTERTHEPAGEYOURAPPURLPOINTSTOHERE', // channel.html file 
oauth : true 
});

<div id="dontLike">
    PAGE IS <b>NOT</b> Liked
</div>

</form>

打开页面的代码隐藏。我们验证了代码签名请求。

public bool ValidateSignedRequest()
    {
        var VALID_SIGNED_REQUEST = Request.Form["signed_request"];

        string applicationSecret = "YOURAPPSECRET";
        string[] signedRequest = VALID_SIGNED_REQUEST.Split('.');
        string expectedSignature = signedRequest[0];
        string payload = signedRequest[1];

        // Attempt to get same hash
        var Hmac = SignWithHmac(UTF8Encoding.UTF8.GetBytes(payload), UTF8Encoding.UTF8.GetBytes(applicationSecret));
        var HmacBase64 = ToUrlBase64String(Hmac);

        return (HmacBase64 == expectedSignature);
    }

   private string ToUrlBase64String(byte[] Input)
    {
        return Convert.ToBase64String(Input).Replace("=", String.Empty)
                                            .Replace('+', '-')
                                            .Replace('/', '_');
    }

    private byte[] SignWithHmac(byte[] dataToSign, byte[] keyBody)
    {
        using (var hmacAlgorithm = new HMACSHA256(keyBody))
        {
            hmacAlgorithm.ComputeHash(dataToSign);
            return hmacAlgorithm.Hash;
        }
    }

 public Dictionary<string, string> DecodePayload(string payload)
    {
        //Remove the bad part of signed_request
        //Begin
        string[] sB64String = payload.Split('.');
        payload = payload.Replace((sB64String[0] + "."), string.Empty);
        //End
        var encoding = new UTF8Encoding();
        var decodedJson = payload.Replace("=", string.Empty).Replace('-', '+').Replace('_', '/');
        var base64JsonArray = Convert.FromBase64String(decodedJson.PadRight(decodedJson.Length + (4 - decodedJson.Length % 4) % 4, '='));
        var json = encoding.GetString(base64JsonArray);
        var jObject = JObject.Parse(json);
        var parameters = new Dictionary<string, string>();

        parameters.Add("page", ((bool)jObject["page"]["liked"]).ToString());
        parameters.Add("admin", ((bool)jObject["page"]["admin"]).ToString());
        return parameters;
    }

protected void pageLike()
    {
        string pageLiked = string.Empty;
        var signed_request = Request.Form["signed_request"];
        var json = DecodePayload(signed_request);


        foreach (KeyValuePair<string, string> objKVP in json)
        {
            //Note You can also see if a user is an admin by replacing the objKVP.Key with admin
            if (objKVP.Key == "page" && objKVP.Value == "True")
            {
                Response.Redirect("https://www.YOURSITE.com/facebook/app/pageLiked.aspx");
                litJson.Text += objKVP.Key + " - " + objKVP.Value + "<br />";
            }
        }
    }

    protected void Page_Load(object sender, EventArgs e)
        {
        pageLike();
    }

您可以在此链接中看到此示例：http://blog.daniellecopp.com/2012/03/19/detect-if-facebook-user-likes-your-page-with-asp-net-2/#comment-52

如何使用FB C＃SDK强制登录Facebook？

1 个答案: