二、打造实体基类
关系型数据表中一般有共性的部分是所有的实体都有ID(但ID的类型不一样),很多业务表都有主从的关系。
2.1表定义
比如下面的表
- CREATE TABLE [lt_dictionary].[City](
- [CityID] [int] IDENTITY(1,1) NOT NULL,
- [Name] [nvarchar](50) NOT NULL,
- [PostalCode] [dbo].[PostalCodeType] NOT NULL,
- [DistanceCode] [nvarchar](5) NOT NULL,
- [Province] [nvarchar](3) NOT NULL,
- [Longitude] [decimal](5, 2) NOT NULL,
- [Latitude] [decimal](5, 2) NOT NULL,
- [Enable] [dbo].[EnableType] NOT NULL CONSTRAINT [DF_City_Enable] DEFAULT ((1)),
- [LastEditDate] [dbo].[BusinessDateType] NOT NULL CONSTRAINT [DF_City_LastEditDate] DEFAULT (getdate()),
- [UpdateDay] AS (datediff(day,[LastEditDate],getdate())),
- [Version] [timestamp] NOT NULL,
- CONSTRAINT [PK_City] PRIMARY KEY CLUSTERED
- (
- [CityID] ASC
- )
这个城市表的ID是int的。
BusinessOrders定义
- CREATE TABLE [lt_business].[BusinessOrders](
- [BusinessOrderID] [uniqueidentifier] NOT NULL CONSTRAINT [DF_BusinessOrders_BusinessOrderID] DEFAULT (newid()),
- [Number] [dbo].[BusinessOrderType] NOT NULL CONSTRAINT [DF_BusinessOrders_Number] DEFAULT ([dbo].[CreateBusinessOrderNumber]('Bz')),
- [Deadline] [dbo].[BusinessDateType] NOT NULL,
- [PaymentMethod] [nchar](2) NOT NULL,
- [PaymentEnterprise] [dbo].[DescriptionType] NOT NULL,
- [Origin] [dbo].[DescriptionType] NOT NULL,
- [Destination] [dbo].[DescriptionType] NOT NULL,
- [DeliveryType] [nchar](2) NOT NULL,
- [Level] [dbo].[LevelType] NOT NULL,
- [Remark] [dbo].[DescriptionType] NOT NULL,
- [Indicator] [nvarchar](3) NOT NULL,
- [FreightPayable] [dbo].[DescriptionType] NOT NULL,
- [WarehouseID] [int] NOT NULL,
- [OrderID] [uniqueidentifier] NOT NULL,
- [BusinessDate] [dbo].[BusinessDateType] NOT NULL CONSTRAINT [DF_BusinessOrders_BusinessDate] DEFAULT (getdate()),
- [StaffID] [int] NOT NULL,
- [Version] [timestamp] NOT NULL,
- [State] AS ([dbo].[GetBusinessOrderState]([BusinessOrderID])),
- CONSTRAINT [PK_BusinessOrders] PRIMARY KEY CLUSTERED
BusinessOrders的ID是uniqueidentifier类型。
BusinessOrderDetaileds定义
- CREATE TABLE [lt_business].[BusinessOrderDetaileds](
- [BusinessOrderDetailedID] [uniqueidentifier] NOT NULL CONSTRAINT [DF_BusinessOrderDetaileds_BusinessOrderDetailedID] DEFAULT (newid()),
- [BusinessOrderID] [uniqueidentifier] NOT NULL,
- [Serial] [int] NOT NULL,
- [GoodsDescription] [dbo].[DescriptionType] NOT NULL,
- [Packing] [nvarchar](2) NOT NULL,
- [Quantity] [decimal](18, 2) NOT NULL,
- [TotalPackages] [decimal](18, 2) NOT NULL,
- [Weight] [decimal](18, 2) NOT NULL,
- [Measurement] [decimal](18, 2) NOT NULL,
- [Version] [timestamp] NOT NULL,
- [State] AS ([dbo].[GetBusinessOrderItmeState]([BusinessOrderDetailedID])),
- [CompleteQuantity] AS ([dbo].[GetBusinessOrderItmeCompleteQuantity]([BusinessOrderDetailedID])),
- CONSTRAINT [PK_BusinessOrderDetaileds] PRIMARY KEY CLUSTERED
BusinessOrderDetaileds的ID是uniqueidentifier类型,其外键对应的是BusinessOrders实体的ID。
2.2关于实体基类定义的要求
我希望有这个的实体基类,该实体定义了所有的继承者(实体的具体实现类)都必须有ID属性,但ID属性的数据类型由各实体自己定义。我还希望,能在类的定义上看出有主从表的关系,并且能约束主从表的一些行为。而且我还希望基类能自动的实现对属性的赋值。
2.3定义EntityBase
EntityBase定义(继承部分)
- [Serializable]
- public abstract class EntityBase<T,ID> where T : EntityBase<T,ID>
- {
- /// <summary>
- /// 所有的实体都必须有一个唯一标识,具体类型有实体各自实现
- /// </summary>
- [System.ComponentModel.DataObjectField(true, true, false)]
- public virtual ID Identity
- {
- set;
- get;
- }
- }
EntityBase定义了一个ID的泛型,该泛型描述了继承者必须实现具体的ID类型。
2.4定义EntityBase的Undo功能
在没有泛型的年代时,基类无了解子类的类型,因此基类只能实现一些返回或参数是基本数据类型的方法,如果要为子类提供个性化的方法,基类只能以object对象返回,且要求子类实现数据类型的强制转换。但现在,EntityBase还提供了一个T类型,因此我们可以实现Undo的功能。
EntityBase(Undo部分)
- /// <summary>
- /// 实体是否支持撤销
- /// </summary>
- public abstract bool HasUndo
- {
- get;
- }
- /// <summary>
- /// 还可以撤销的次数
- /// </summary>
- public int UndoCount
- {
- get
- {
- return undoStack.Count;
- }
- }
- /// <summary>
- /// 得到实体的副本
- /// </summary>
- /// <returns></returns>
- protected virtual T Clone()
- {
- return (T)this.MemberwiseClone();
- }
- /// <summary>
- /// 将复本入栈
- /// </summary>
- protected void Push()
- {
- if (this.HasUndo)
- {
- this.Push((T)this.Clone());
- }
- }
- /// <summary>
- /// 将复本入栈
- /// </summary>
- /// <param name="obj"></param>
- private void Push(T obj)
- {
- if (this.HasUndo)
- {
- undoStack.Push(obj.Clone());
- }
- }
- private System.Collections.Generic.Stack<T> undoStack = new Stack<T>();
- /// <summary>
- /// 将复本出栈
- /// </summary>
- /// <returns></returns>
- private T Pop()
- {
- if (undoStack.Count > 0)
- {
- return undoStack.Pop();
- }
- else
- {
- return null;
- }
- }
- /// <summary>
- /// 撤销
- /// </summary>
- /// <returns></returns>
- public T Undo()
- {
- return Pop();
- }
使用了泛型,我们在类的内部提供了泛型队列,然后返回值和参数值都是泛型T,该T将由各个子类来具体实现。
2.5定义EntityBase的数据访问能力
- /// <summary>
- /// 根据给定的连接字符串构造数据提供者
- /// </summary>
- /// <param name="connStr"></param>
- /// <returns></returns>
- protected static DataProviders.IDataProvider CreateDataProvider(string connStr)
- {
- return new DataProviders.SqlDataProvider.SqlDataProvider(connStr);
- }
2.6定义EntityBase的构造函数
EntityBase有一个接受System.Data.DataTable的构造函数,该构造函数将table中指定行的数据和本类的属性作对比,如果名称和数据类型匹配,则自动赋值。
EntityBase构造函数
- /// <summary>
- /// 按table的指定行数据进行属性的初始化
- /// </summary>
- /// <param name="table"></param>
- /// <param name="indexRow"></param>
- public EntityBase(System.Data.DataTable table, int indexRow)
- {
- //遍历table中的每一列
- for (int i = 0; i <= table.Columns.Count - 1; i++)
- {
- //按列的名称,试图从当前对象中获取同名属性
- System.Reflection.PropertyInfo pinfo = this.GetType().GetProperty(table.Columns[i].ColumnName);
- if (pinfo != null)
- {//如果存在该属性
- object value = table.Rows[indexRow][table.Columns[i].ColumnName];//提取列的当前行值
- if (pinfo.PropertyType == table.Columns[i].DataType)//如果对象属性定义的类型和table的列的类型一致
- {
- pinfo.SetValue(this, value, null);//赋值
- }
- else
- {
- if (pinfo.PropertyType.IsEnum)//如果对象属性的值是枚举类型
- {
- if (value.GetType() == typeof(int))//数据库中保存的是int类型,则直接为枚举赋值
- {
- pinfo.SetValue(this, value, null);//赋值
- }
- if (value.GetType() == typeof(string))//如果数据库中保存的是string类型
- {
- pinfo.SetValue(this, Enum.Parse(pinfo.PropertyType, value.ToString(), false), null);//赋值
- }
- }
- //如果对象的属性是Bitmap类型,对应的数据值是byte[]
- if (pinfo.PropertyType==typeof(System.Drawing.Bitmap) && value.GetType()==typeof(byte[]))
- {
- pinfo.SetValue(this, new System.Drawing.Bitmap(new System.IO.MemoryStream((byte[])value)), null);//赋值
- }
- }
- }
- }
- }
2.7定义EntityBase的CreateInstance
虽然EntityBase的构造函数有能力实现对属性的自动赋值,但我们可能要实例对象的集合或决定table中是否有值,应此我们需要实现CreateInstance方法。
定义EntityBase的CreateInstances方法
- /// <summary>
- /// 通过table实例化一组对象
- /// </summary>
- /// <param name="table"></param>
- /// <returns></returns>
- public static List<T> CreateInstances(System.Data.DataTable table, int startRecord, int maxRecords)
- {
- List<T> instances = new List<T>();
- for (int i = startRecord; i <= maxRecords; i++)
- {
- instances.Add(CreateInstance(table, i));
- }
- return instances;
- }
- /// <summary>
- /// 通过table实例化一个对象
- /// </summary>
- /// <param name="table"></param>
- /// <param name="startRecord"></param>
- /// <param name="maxRecords"></param>
- /// <returns></returns>
- public static T CreateInstance(System.Data.DataTable table, int rowIndex)
- {
- if (table.Rows.Count > rowIndex)
- {
- return (T)System.Activator.CreateInstance(typeof(T), table, rowIndex);
- }
- else
- {
- return null;
- }
- }
- /// <summary>
- /// 默认按table的第一行实例化一个对象
- /// </summary>
- /// <param name="table"></param>
- /// <returns></returns>
- public static T CreateInstance(System.Data.DataTable table)
- {
- return CreateInstance(table, 0);
- }
- /// <summary>
- /// 通过table实例化一组对象
- /// </summary>
- /// <param name="table"></param>
- /// <param name="startRecord"></param>
- /// <returns></returns>
- public static List<T> CreateInstances(System.Data.DataTable table, int startRecord)
- {
- return CreateInstances(table, startRecord, table.Rows.Count - 1);
- }
- /// <summary>
- /// 通过table实例化一组对象
- /// </summary>
- /// <param name="table"></param>
- /// <returns></returns>
- public static List<T> CreateInstances(System.Data.DataTable table)
- {
- return CreateInstances(table, 0, table.Rows.Count - 1);
- }
http://blog.51cto.com/shyleoking/805800