According to my knowledge you have to create a class first and in that class override these events and to trigger these events you have to create that class object and return to your repo layer For example:

     public class AppNameDatabase : Database
        {

            public AppNameDatabase (DbConnection connection) : base(connection)
            {
            }
protected override bool OnInserting(InsertContext insertContext)
    {
        if (insertContext.Poco is CommonEntity entity)
        {
            entity.DateInserted = DateTime.UtcNow;
        }

        return base.OnInserting(insertContext);
    }

    protected override bool OnUpdating(UpdateContext updateContext)
    {
        var entity = updateContext.Poco as CommonEntity;
        if(entity != null)
        {
            entity.DateModified = DateTime.UtcNow;
        }

        return base.OnUpdating(updateContext);
    }

    }

At last create a factory class to encapsulate it further

    public class DatabaseFactory : IDatabaseFactory
        {
      readonly DbConnection _connection;

            public DatabaseFactory(DbConnection connectionl)
            {
                 _connection=connection;
            }
 public IDatabase GetDbConnection()
        {
            using (var dbContext = new AppNameDatabase (_connection)
            {
                return dbContext;
            }
        }
    }

You can ask if you have any further questions

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