Facebook redirect url issue OAuthException

Question

My app was working well for long time, but now I am getting the error from Facebook saying:

Content: {\"error\":{\"message\":\"Error validating verification c

Answer 1

Mo Hrad A is right, I didn't even manage to use $ character.

I wrote 2 simple functions that allows me to use complex return urls with parameters:

public static string EncodeFacebookReturnUrl(string url)
{
    return Regex.Replace(HttpUtility.UrlEncode(url), "%", "_-_");
}

public static string DecodeFacebookReturnUrl(string url)
{
    return HttpUtility.UrlDecode(Regex.Replace(url, "_-_", "%"));
}

Translating with UrlEncode results in only 1 "illegal" character (%), which I'm replacing with the legal string _-_. Makes it simple to decode too.