ASP.NET Gravatar Control

March 13, 2007

Gravatar 2.0 has been out for a few weeks now and I didn't see any ASP.NET implementation listed on their site so I figured I would wip one up.

It is pretty simple to implement a Gravatar. All you need to do is set the src attribute of an img tag to a location on Gravatar's domain. The src attribute has a few parameters, but the only "tricky" one is an MD5 hash of the users email address.

Here is the code:

public class Gravatar : System.Web.UI.WebControls.Image
    #region Rating property
    public enum GravatarRating { G, PG, R, X }
    private GravatarRating _Rating = GravatarRating.G;
    public GravatarRating Rating
        get { return _Rating; }// get
        set { _Rating = value; }// set
    }// property


    #region Size property
    private int _Size = 80;
    /// An optional "size" parameter may follow that specifies the desired width and height of the gravatar. Valid values are from 1 to 80 inclusive. Any size other than 80 will cause the original gravatar image to be downsampled using bicubic resampling before output.
    public int Size
            if (_Size <= 0)
                return 80;
            if (_Size > 80)
                return 80;
            return _Size;
            _Size = value;
            base.Width = value;
            base.Height = value;
        }// set
    }// property

    #region Email property
    private string _Email;
    public string Email
        get { return _Email; }// get
        set { _Email = value; }// set
    }// property


    #region DefaultImageUrl property
    private string _DefaultImageUrl;

    public string DefaultImageUrl
        get { return _DefaultImageUrl; }// get
        set { _DefaultImageUrl = value; }// set
    }// property


    #region Hide some members
    new private string ImageUrl { get { return String.Empty; } }
    /// Gravatar only supports a size property
    new private int Width { get { return Size; } }
    new private int Height { get { return Size; } }

    protected override void Render(System.Web.UI.HtmlTextWriter writer)
        System.Text.StringBuilder image = new System.Text.StringBuilder();

        if (!String.IsNullOrEmpty(DefaultImageUrl))

        base.ImageUrl = image.ToString();

    private string MD5HashMe(string email)
        System.Text.Encoder enc = System.Text.Encoding.Unicode.GetEncoder();
        byte[] unicodeText = new byte[email.Length * 2];
        enc.GetBytes(email.ToCharArray(), 0, email.Length, unicodeText, 0, true);

        System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
        byte[] result = md5.ComputeHash(unicodeText);

        System.Text.StringBuilder sb = new System.Text.StringBuilder();
        for (int i = 0; i < result.Length; i++)

        return sb.ToString();

To use this control all you need to do is add the following to your .aspx page:

<%@ Register TagPrefix="CC" Assembly="CarKnee.Controls" Namespace="CarKnee.Controls" %>

The code is also available for download (1 KB).

Comments (2) -

Dave Burke

I don't get it, Carknee.  Looks like you did a great job on the .NET implementation though.  If you feel like blogging about it after you've used it a bit with an example of it in action, that would help thick guys like me understand its usefulness.  Regards!

Sean Kearney

Hi Dave,
The Gravatar control isn't for Community Server. In order to make it work with CS I would need to modify the "Leave a Comment" form to store an email address and I don't see the point with CS 2007 hanging overhead.

Now, with CS 2007 and Ben's nice Utility Controls we can hook this up without any core changes!

This was just a silly 15 minute exercise to take my mind off my existing projects.

Comments are closed