Domain Object Layer Design and Sample Code for LiteMDA

Source Codes in C# 2.0 Format Download

In these sample codes, BaseObject.cs, ICondition.cs, IPersistable.cs and ObjectCollection.cs are shared classes are for all Domain Objects. And IUserData.cs, UserData.cs and User.cs represent a Domain Object “User”, mapping to Table “User” in a RDB when using a RDB.

Sample Domain Object “User” and “ObjectCollection<User>” (C# 2.0 Generic Style Class) represent a single user and user’s collection. They are all inheriting IPersistable, so need to implementing “Save” and “Load” methods of IPersistable. Class “User” inherits BaseObject<UserData> which provides “User” the special custom batch Update support.

With the help of the following four methods, we can do all kinds of “Read” and “Write” to “User”: User.Save, User.Load, ObjectCollection<User>.Save, ObjectCollection<User>.Load and BaseObject<UserData>.BatchUpdate.

And with the benefit of C# 2.0’s Generic, codes become more clearly than un-generic style implementing.

IUserData.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestDomainObject0808
{
    public interface IUserData
    {
        int? ID { get; set; }
        string Name { get; set; }
    }
}

UserData.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestDomainObject0808
{
    public class UserData : IUserData
    {
        Private Members#region Private Members

        private int? _ID;
        private string _Name = null;

        #endregion

        Attributes#region Attributes

        public int? ID
        {
            get
            {
                return _ID;
            }
            set
            {
                _ID = value;
            }
        }

        public string Name
        {
            get
            {
                return _Name;
            }
            set
            {
                _Name = value;
            }
        }

        #endregion

        Constructors#region Constructors

        public UserData()
        {
        }

        #endregion
    }
}

IPersistable.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestDomainObject0808
{
    public interface IPersistable
    {
        void Save();
        void Load(ICondition condition);
    }
}

BaseObject.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestDomainObject0808
{
    public abstract class BaseObject<ObjectType>
    {
        public static void BatchUpdate(ICondition condition, ObjectType obj)
        {
            //Only un-null/HasValue attributes will be treated as need-to-update attributes
            //
        }
    }
}

ICondition.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestDomainObject0808
{
    public interface ICondition
    {
        //ICondition will be OO style, and should be either designtime static definition 
        //in configuration file or runtime dynamically constructed ones in codes or 
        //free combinations of them.
    }
}

User.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestDomainObject0808
{
    public class User : BaseObject<IUserData>, IUserData, IPersistable
    {
        Private Members#region Private Members

        private IUserData _OldData = null;
        private IUserData _CurrentData = null;
        private void RestoreOldData()
        {
            _CurrentData = new UserData();
            _CurrentData.ID = _OldData.ID;
            _CurrentData.Name = _OldData.Name;
        }

        #endregion

        Attributes#region Attributes

        public int? ID
        {
            get
            {
                return _CurrentData.ID;
            }
            set
            {
                _CurrentData.ID = value;
            }
        }

        public string Name
        {
            get
            {
                return _CurrentData.Name;
            }
            set
            {
                _CurrentData.Name = value;
            }
        }

        #endregion

        Constructors#region Constructors

        public User()
        {
            _OldData = new UserData();
            RestoreOldData();
        }

        public User(IUserData ud)
        {
            _OldData = (ud == null? new UserData() : ud);
            RestoreOldData();
        }

        public User(ICondition condition) : this()
        {
            Load(condition);
        }

        #endregion

        IPersistable#region IPersistable

        public void Save()
        {
            //Save()'s implementing denpending on the configuration setting for current DO's primary key and user defined type attributes;
            //If _CurrentData.PK == null then do Creating New Object in persisting;
            //else _CurrentData.PK != null then do Updating Object in persisting.
            //When do Updating Object, compare the _OldData and _CurrentData's Attributes' values, and 
            //dynamically construct minimal update operation.
            //For user defined type attributes, need do recursively Saving on attributes of this kind.
            //
        }

        public void Load(ICondition condition)
        {
            //Load object data according to specified condition
            //
        }

        #endregion
    }
}

ObjectCollection.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace TestDomainObject0808
{
    public class ObjectCollection<ObjectType> : List<ObjectType>, IPersistable
        where ObjectType : IPersistable
    {
        Constructors#region Constructors

        public ObjectCollection() : base()
        {
        }

        public ObjectCollection(ICondition condition)
            : this()
        {
            Load(condition);
        }

        #endregion

        IPersistable#region IPersistable

        public void Save()
        {
            foreach (ObjectType obj in this)
            {
                obj.Save();
            }
        }

        public void Load(ICondition condition)
        {
            this.Clear();

            if (condition != null)
            {
                //Load objects according to specified condition
                //
            }
        }

        #endregion
    }
}

//The End