Facebook SDK on Windows phone 7 throws (OAuthException) (#210) User not visible

I am using Facebook SDK(Codeplex) on Windows Phone 7.

When I try to write on Friends Wall, I get this exception raised ((OAuthException) (#210) User not visible)

Below is my query

private string requestedFbPermissions = "user_about_me,publish_stream";
//
var parms = new Dictionary<String, object>();
parms["display"] = "touch";
parms["client_id"] = apiKey;
parms["scope"] = requestedFbPermissions;
parms["type"] = "user_ag开发者_高级运维ent";

try
{
    string feedRequest = selectedUID + "/feed?message=\'Test Msg\'";

    fbApp.PostAsync(feedRequest, parms, (value) =>
    {
        object result = value.Result;
        JObject stuff = JObject.Parse(value.Result.ToString());
    }
}

Am i missing something , for some friends i am able to write on wall successfully.

You're probably using the wrong user ID of the friend -- if you try to post to the wall of someone with whom you're not friends, the API will return error #201 "User not visible". Double-check that you're using the correct user ID, and that you're friends with that user.

What i guess that user has not allowed particular user to post to its wall. It happned with me too i used same C#sdk