Here is a quick little URL Helper extension method to add Gravatar images/photos/avatars to your page:

public static string GravatarUrl(this UrlHelper url, string email, int size)

{

    string imageUrl = ConfigurationManager.AppSettings["DefaultGravatar"];

    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);

}

It uses another custom URL Helper extension method Absolute to generate an absolute URL to a default image (based on an application relative url).

The Absolute extension method is similar to the ActionAbsolute method I posted earlier:

public static string Absolute(this UrlHelper url, string contentUrl)

{

    return new Uri(GetBaseUrl(url), url.Content(contentUrl))

        .AbsoluteUri;

}

And it also used the MD5 extension method from yesterdays post.

ASP.NET MVC · Extension Methods · Gravatar

A nifty little extension method that generated the MD5/SHA-1 hash of a string. These methods are a continuation of my previous post:

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;

}

Just substitute MD5 for SHA1, SHA256, SHA384, SHA512 or RIPEMD160 which ever hash algorithm fits your needs.

Extension Methods · hash · md5 · Secure Hash

Showing an absolute date on a webpage, e.g. January 22, 2009 13:01, is of course a very normal way to do it, apart from various different date formats, it is easily read and consumed. However if the date is shown in a context where the absolute date is of little importance, but it is more important to know if it was a long time ago, just now or maybe just in a couple of minutes, a relative and more descriptive method is better.

For example the date mentioned above might be described as “8 months ago”. Just by giving it a quick glance you get an idea about when this event occurred.

For this here are a couple of extension methods that generate this descriptive text based on a given time:

public static string ToRelativeTime(this DateTime from)

{

    DateTime now = DateTime.Now;

    return from.ToRelativeTime(now);

}


public static string ToRelativeTime(this DateTime from, bool usePreAndSuffix)

{

    DateTime now = DateTime.Now;

    return from.ToRelativeTime(now, usePreAndSuffix);

}


public static string ToRelativeTime(this DateTime from, DateTime to)

{

    return from.ToRelativeTime(to, true);

}


public static string ToRelativeTime(this DateTime from, DateTime to, bool usePreAndSuffix)

{

    string prefix = usePreAndSuffix && (from > to) ? "in " : string.Empty;

    string suffix = !usePreAndSuffix || (from > to) ? string.Empty : " ago";

    // is more than 1 year?


    if (from > to)

    {

        DateTime d = from;

        from = to;

        to = d;

    }


    int years = to.Year - from.Year;

    if ((to.Month < from.Month) || ((to.Month == from.Month) && (to.Day < from.Day)))

    {

        years--;

    }


    if (years > 1)

    {

        return string.Format("{0}{1} years{2}", prefix, years, suffix);

    }

    else if (years == 1)

    {

        return string.Format("{0}1 year{1}", prefix, suffix);

    }


    // less than 1 year, is more than 1 month?


    int months = to.Month - from.Month;

    if (months < 0)

    {

        months += 12;

    }

    if ((to.Day < from.Day) || ((to.Day == from.Day) && (to.TimeOfDay < from.TimeOfDay)))

    {

        months--;

    }


    if (months > 1)

    {

        return string.Format("{0}{1} months{2}", prefix, months, suffix);

    }

    else if (months == 1)

    {

        return string.Format("{0}1 month{1}", prefix, suffix);

    }


    // less than 1 month, is more than 1 day/week?


    TimeSpan diff = to - from;


    if (diff.Days > 7)

    {

        return string.Format("{0}{1} weeks{2}", prefix, diff.Days / 7, suffix);

    }

    else if (diff.Days > 1)

    {

        return string.Format("{0}{1} days{2}", prefix, diff.Days, suffix);

    }

    else if (diff.Days == 1)

    {

        return string.Format("{0}1 day{1}", prefix, suffix);

    }


    // less than 1 day, is more than 1 hour?


    if (diff.Hours > 1)

    {

        return string.Format("{0}{1} hours{2}", prefix, diff.Hours, suffix);

    }

    else if (diff.Hours == 1)

    {

        return string.Format("{0}1 hour{1}", prefix, suffix);

    }


    // less than 1 hour, is more than 1 minute?


    if (diff.Minutes > 1)

    {

        return string.Format("{0}{1} minutes{2}", prefix, diff.Minutes, suffix);

    }

    else if (diff.Minutes == 1)

    {

        return string.Format("{0}1 minute{1}", prefix, suffix);

    }


    // less than 1 minute


    if (diff.Seconds == 1)

    {

        return string.Format("{0}1 second{1}", prefix, suffix);

    }

    else if (diff.Seconds < 1)

    {

        return string.Format("{0}less than 1 second{1}", prefix, suffix);

    }


    return string.Format("{0}{1} seconds{2}", prefix, diff.Seconds, suffix);

}

This can of course be optimized for localization etc.

Dates · Extension Methods