GetMD5

public static string GetMD5(string fileName)
{
    try {
        var file = new FileStream(fileName, FileMode.Open);
        var md5 = new MD5CryptoServiceProvider();
        byte[] retVal = md5.ComputeHash(file);
        file.Close();
        file.Dispose();

        var sb = new StringBuilder();

        foreach (var t in retVal)
            sb.Append(t.ToString("x2"));

        return sb.ToString();
    }
    catch { return ""; }
}