Get gravatar URL from Email

gistfile1.cs

public static string GravatarUrl(this UrlHelper url, string email, int size)
{
    string imageUrl = ConfigurationManager.AppSettings["DefaultGravatar"]; // e.g. "identicon" or a URL to image
    if (imageUrl.StartsWith("~/"))
    {
        imageUrl = url.Absolute(imageUrl);
    }

    if (string.IsNullOrEmpty(email))
    {
        return imageUrl;
    }

    string md5 = email.ToLowerInvariant().MD5();
    return string.Format(
        "http://www.gravatar.com/avatar/{0}.jpg?d={1}&s={2}&r=g",
        md5.ToLowerInvariant(),
        url.Encode(imageUrl),
        size);
}

public static string GravatarUrl(this UrlHelper url, string email)
{
    return url.GravatarUrl(email, 32);
}

public static Uri GetBaseUrl(this UrlHelper url)
{
    Uri contextUri = new Uri(url.RequestContext.HttpContext.Request.Url, url.RequestContext.HttpContext.Request.RawUrl);
    UriBuilder realmUri = new UriBuilder(contextUri) { Path = url.RequestContext.HttpContext.Request.ApplicationPath, Query = null, Fragment = null };
    return realmUri.Uri;
}

public static string Absolute(this UrlHelper url, string contentUrl)
{
    return new Uri(GetBaseUrl(url), url.Content(contentUrl)).AbsoluteUri;
}

public static string MD5(this string value)
{
    System.Security.Cryptography.MD5 algorithm =
        System.Security.Cryptography.MD5.Create();

    byte[] data = Encoding.ASCII.GetBytes(value);
    data = algorithm.ComputeHash(data);
    string md5 = "";
    for (int i = 0; i < data.Length; i++)
    {
        md5 += data[i].ToString("x2").ToLower();
    }

    return md5;
}