SilverLight商业应用程序开发---学习笔记(3)

创建Presentation Model 类

Presentation Model类用于如下情况：

1）在应用程序中不使用EF model；

2）不想让显示层与数据访问层进行共享，保持两层之间的独立性；

3）模块中的实体与显示层并不是一对一的匹配关系，显示的数据可能是多个实体聚合的结果；

4）需要统计数据（求和，平均等）；

5）需要格式化数据从而适合显示界面；

创建Presentation Model类步骤如下：

构建类，包含所有需要在客户端显示的属性；
构建域服务类，继承自DomainService；
手工配置get/query域操作，暴露给Presentation model；
需要进行数据编辑，手工实现insert/update/delete操作
实例：

1、注意事项：

至少有一个属性以Key特性修饰，指定其为主键；
可以使用所有修饰特性标记；如果不想在类上修饰，也可以建立相应的元数据类，添加相应的修饰；
Presentation model类可以根据需要放置在解决方案中的适当项目中，不限于Web项目中；
2、具体实现

1）在Web项目的Models文件夹下创建一个新类，命名为ProductSummary。

2）向类中添加适当引用，添加相应属性，代码如下：

using System;
using System.ComponentModel.DataAnnotations;

namespace AdventureWorks.Web.Models
{
public class ProductSummary
{
[Key]
[Editable(false)]
public int       ID                   { get; set; }
public string    Name                 { get; set; }
public string    Number               { get; set; }
public decimal   ListPrice            { get; set; }
public byte[]    ThumbnailPhoto       { get; set; }
public int?      QuantityAvailable    { get; set; }
public string    Category             { get; set; }
public string    Subcategory          { get; set; }
public string    Model                { get; set; }
public bool      MakeFlag             { get; set; }
public DateTime  ModifiedDate         { get; set; }
}
}

3、填充或暴露Presentation Model类型：

1）在Web项目的Service文件夹，使用Domain Service Class项目模板，添加一个名为ProductSummaryService的域服务类。因为数据仍然是取自于实体模型，因此需要选择AdventureWorksEntities实体模型作为对象上下文。不要选择实体列表中的任何实体，只需要点击OK按钮。这就创建了空白的域服务：

namespace AdventureWorks.Web.Services
{
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Data;
using System.Linq;
using System.ServiceModel.DomainServices.EntityFramework;
using System.ServiceModel.DomainServices.Hosting;
using System.ServiceModel.DomainServices.Server;
using AdventureWorks.Web;

// Implements application logic using the AdventureWorksEntities context.
// TODO: Add your app logic to these methods or in additional methods.
// TODO: Wire up authentication (Windows/ASP.NET Forms) and uncomment the
// following to disable anonymous access.
// Also consider adding roles to restrict access as appropriate.
// [RequiresAuthentication]
[EnableClientAccess()]
public class ProductSummaryService :
LinqToEntitiesDomainService<AdventureWorksEntities>
{

}
}

2）添加对AdventureWorks.Web.Models名称空间的引用；

3）向域服务中添加查询操作，要求返回IQueryable集合类型：

public IQueryable<ProductSummary> GetProductSummaryList()
{
return from p in this.ObjectContext.Products
select new ProductSummary()
{
ID = p.ProductID,
Name = p.Name,
Number = p.ProductNumber,
ListPrice = p.ListPrice,
ThumbnailPhoto = p.ProductProductPhotoes.FirstOrDefault().
ProductPhoto.ThumbNailPhoto,
QuantityAvailable = p.ProductInventories
.Sum(pi => pi.Quantity),
Category = p.ProductSubcategory.ProductCategory.Name,
Subcategory = p.ProductSubcategory.Name,
Model = p.ProductModel.Name,
MakeFlag = p.MakeFlag,
ModifiedDate = p.ModifiedDate
};
}

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4、编辑Presentation Model

1）Insert，Update，Delete域操作方法的命名与签名与前述要求一致：

public void InsertProductSummary(ProductSummary productSummary)
{

}

public void UpdateProductSummary(ProductSummary productSummary)
{

}

public void DeleteProductSummary(ProductSummary productSummary)
{

}

2）Insert方法实现：

public void InsertProductSummary(ProductSummary productSummary)
{
Product product = new Product();
product.Name = productSummary.Name;
product.ProductNumber = productSummary.Number;
product.ListPrice = productSummary.ListPrice;
product.ModifiedDate = DateTime.Now;

// Need to set default values for these properties,
// otherwise the save will fail
product.SellStartDate = DateTime.Now;
product.SafetyStockLevel = 1;
product.ReorderPoint = 1;

this.ObjectContext.Products.AddObject(product);
}

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3）Update方法实现

public void UpdateProductSummary(ProductSummary productSummary)
{
Product product = this.ObjectContext.Products
.Where(p => p.ProductID == productSummary.ID)
.First();
product.Name = productSummary.Name;
product.ProductNumber = productSummary.Number;
product.ListPrice = productSummary.ListPrice;
product.ModifiedDate = DateTime.Now;
}

4）删除方法实现：

public void DeleteProductSummary(ProductSummary productSummary)
{
Product product = new Product();
product.ProductID = productSummary.ID;
product.ModifiedDate = productSummary.ModifiedDate;
this.ObjectContext.AttachTo("Products", product);
this.ObjectContext.DeleteObject(product);
}

4、将自动生成属性值返回客户端

当插入（或更新）数据到服务器后，通常需要将保存的数据再返回到客户端，可以通过域服务的ChangeSet对象的Associate方法实现。下面的实例介绍的场景是：向数据库插入一条新记录以后，刚刚更新的Product实体的ProductId与ModifiedDate属性值返回客户端，更新ProductSummary对象：

1）在ProductSummaryService类中添加如下的回调方法。该方法将更新ProductSummary对象的ProductId与ModifiedDate属性，返回值到客户端：

private void UpdateProductSummaryValues(ProductSummary productSummary,
Product product)
{
productSummary.ID = product.ProductID;
productSummary.ModifiedDate = product.ModifiedDate;
}

2）调用ChangeSet对象的Associate方法，通知回调方法的调用时机为Product实体持久化数据库之后：

public void InsertProduct(ProductSummary productSummary)
{
Product product = new Product();
product.Name = productSummary.Name;
product.ProductNumber = productSummary.Number;
product.ListPrice = productSummary.ListPrice;
product.ModifiedDate = DateTime.Now;

// Need to set default values for these properties,
// otherwise the save will fail.
product.SellStartDate = DateTime.Now;
product.SafetyStockLevel = 1;
product.ReorderPoint = 1;

this.ObjectContext.Products.AddObject(product);
this.ObjectContext.SaveChanges();

ChangeSet.Associate(productSummary, product, UpdateProductSummaryValues);
}

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