Custom dependency injection

/// <summary>

    /// Factory for creating a concrete instance of the tracker base

    /// </summary>

    public static class TrackerFactory

    {

        /// <summary>

        /// Returns a concrete tracker that is specific to the current version of Siteccore.

        /// NOTE: This is an attempt to defend against future changes in the Sitecore analytics API.

        /// </summary>

        /// <returns>A concrete tracker instance</returns>

        public static AbstractTrackerBase GetTracker()

        {

            return new SitecoreDmsTracker();

            // NOTE: implement a new tracker for xDB and return it here

        }

    }

SitecoreDmsTracker is a concrete class (with method implementations) that gets returned here. You can substitute some other class down the road. 

namespace HA.Web.Analytics.Tracking.Base

{

    /// <summary>

    /// Tracker base class defines methods that aren't specific to OMS/DMS/xDB APIs

    /// </summary>

    public abstract class AbstractTrackerBase

    {

        #region Virtual Members

        /// <summary>

        /// Attempts to cancel the current sitecore page, thereby excluding it from Sitecore analytics

        /// </summary>

        /// <returns>true if the page could be canceled</returns>

        public virtual bool TryCancelCurrentPage()

        {

            // Don't bother if analytics isn't running

            if (!IsAnalyticsEnabled())

            {

                return false;

            }

            try

            {

                CancelCurrentPage();

                return true;

            }

            catch

            {

                return false;

            }

        }

=========================

"sealed" must be used for overrides.When applied to a class, the sealed modifier prevents other classes from inheriting from it.

namespace HA.Web.Analytics.Tracking.Trackers

{

    /// <summary>

    /// A DMS specific implementation of the tracker base

    /// </summary>

    public sealed class SitecoreDmsTracker : AbstractTrackerBase

    {

        public const string _VisitorTestTagName = "MULTIVARIATE_TEST_NAME";

        public const string _VisitorTestCookieName = "VisitorMultivariateTestCookie";

        /// <summary>

        /// Determines if the current visitor has a specific pattern card

        /// </summary>

        /// <param name="profileName">The name of the profile grouping</param>

        /// <param name="patternLabel">The name of the pattern label to match</param>

        /// <param name="utcCutoffDateTime">An optional cuttoff date to exclude old data</param>

        /// <returns>true if the visitor has a pattern card</returns>

        public override bool VisitorHasPatternCard(string profileName, string patternLabel, DateTime? utcCutoffDateTime)

        {