A utility class for helping determine if a SharePoint item update event is a result of a publish, approve or just an update.

ItemVersionReader

    /// <summary>
    /// Use in "Updating" event handler to determine if an update is a publish event.
    /// </summary>
    public class ItemVersionReader
    {
        public Version BeforeVersion { get; private set; }
        public int PublishingLevel { get; private set; }
        public int ModerationStatus { get; private set; }
        public bool IsPublishing
        {
            get { return PublishingLevel == 2 && ModerationStatus == 0; }
        }

        public ItemVersionReader(SPItemEventProperties properties)
        {
            BeforeVersion = GetBeforeVersion(properties);

            PublishingLevel = GetAfterLevel(properties);

            ModerationStatus = GetAfterModerationStatus(properties);
        }


        private static Version GetBeforeVersion(SPItemEventProperties properties)
        {
            //Ends up something like "V1.1"
            string beforeVersion = GetPropertyValue(properties.BeforeProperties, "vti_sourcecontrolversion");

            //Not used at present, but helpful for debugging
            string afterVersion = GetPropertyValue(properties.AfterProperties, "vti_sourcecontrolversion");

            return ParseVersionString(beforeVersion, properties.ListItem.Url);
        }

        private static Version ParseVersionString(string version, string itemUrl)
        {
            var majorMinor = new string[0];
            if (version.StartsWith("V", StringComparison.OrdinalIgnoreCase))
            {
                version = version.Substring(1);
                majorMinor = version.Split(new[] { '.' }, StringSplitOptions.RemoveEmptyEntries);
            }
            else
            {
                Debug.WriteLine("The before version of the file at " + itemUrl +
                                " is of an unknown format: " + version);
            }

            if (majorMinor.Length == 2)
            {
                int majorBeforeVersion, minorBeforeVersion;
                if (int.TryParse(majorMinor[0], out majorBeforeVersion)
                    && int.TryParse(majorMinor[1], out minorBeforeVersion))
                {
                    return new Version(majorBeforeVersion, minorBeforeVersion);
                }
            }
            return null;
        }


        private static int GetAfterLevel(SPItemEventProperties properties)
        {
            //Should be 1 or 2 or 255 similar
            //
            //  beforeLevel     afterLevel      Meaning
            //  255             255             minor checkin or overwrite of minor version
            //  255             2               major checkin
            //  2               2               publish / approve

            //Not used at present, but helpful for debugging
            string beforeLevel = GetPropertyValue(properties.BeforeProperties, "vti_level");
            string afterLevel = GetPropertyValue(properties.AfterProperties, "vti_level");

            int level;
            if (!int.TryParse(afterLevel, out level))
            {
                level = -1;
            }
            return level;
        }

        private int GetAfterModerationStatus(SPItemEventProperties properties)
        {
            //Should be 0 (Approved), 1 (Rejected), 2 (Pending) or 3 (Cancelled)
            string afterModerationStatus = GetPropertyValue(properties.AfterProperties, "vti_doclibmodstat");
            int moderationStatus;
            if (!int.TryParse(afterModerationStatus, out moderationStatus))
            {
                moderationStatus = -1;
            }
            return moderationStatus;
        }

        private static string GetPropertyValue(SPItemEventDataCollection props, string propertyName)
        {
            object property = props[propertyName];

            if (property != null)
            {
                string propertyValue = property.ToString();
                Debug.WriteLine(propertyValue);
                return propertyValue;
            }
            else
            {
                Debug.WriteLine(propertyName + " is null");
                return "";
            }
        }
    }