Layers Pattern in Practice

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using BillsEntityLib;

namespace BillsBusinessLogicLib
{
    /// <summary>
    /// Interface for Bill manager business logic
    /// </summary>
    public interface IBillsManager
    {
        /// <summary>
        /// Read from data source
        /// </summary>
        /// <param name="fromDate">From date</param>
        /// <param name="toDate">To date</param>
        /// <returns>List of bills</returns>
        Bills Read(DateTime fromDate, DateTime toDate);

        /// <summary>
        /// Reads a bill by its ID
        /// </summary>
        /// <param name="id">Bills Id</param>
        /// <returns>Bill object</returns>
        Bill ReadById(Guid id);

        /// <summary>
        /// Insert a bill into the database
        /// </summary>
        /// <param name="bill">Bill to insert</param>
        void Insert(Bills bill);

        /// <summary>
        /// Delete a bill from database
        /// </summary>
        /// <param name="bill">Bill to delete</param>
        /// <returns>Number of deleted items</returns>
        int Delete(Guid bill);

        /// <summary>
        /// Delete a list of bills with the specified guids
        /// </summary>
        /// <param name="guids">Guids to delete</param>
        /// <returns>Number of deleted items</returns>
        int Delete(IEnumerable<Guid> guids);

        /// <summary>
        /// Update a bill in the database
        /// </summary>
        /// <param name="billId">BillId to update</param>
        /// <param name="newBill">New bill</param>
        /// <returns>Number of updated items</returns>
        int Update(Guid billId, Bill newBill);

        /// <summary>
        /// Settings
        /// </summary>
        object[] Settings
        {
            get;
            set;
        }
    }
}