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RIA Service中对于递归实体类型处理的问题及解决方案

2011-06-10 11:32 423 查看

故事是这样开始的：

我们在开发一个Silverlight应用程序的时候使用到了RIA Service，我们需要通过该服务公开一个对文件夹的查询操作。

为此，我们建立了如下的一个实体类型

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

using System.Runtime.Serialization;
using System.ComponentModel.DataAnnotations;

using System.ServiceModel.DomainServices.Server;

namespace DomainServiceSample.Web
{
[DataContract]//必须声明类别为DataContract
public class Folder
{
[DataMember]//必须声明属性为DataMember
[Key]//一个用于DomainService的Entity必须有一个Key
public Guid ID { get; set; }

[DataMember]
public string Name { get; set; }

[DataMember]

public Folder[] SubFolder { get; set; }

}
}

【注意】上面其实是有一个递归的类型，也就是Folder里面又包含Folder

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

然后，我们创建了一个DomainService

namespace DomainServiceSample.Web
{
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.ServiceModel.DomainServices.Hosting;
using System.ServiceModel.DomainServices.Server;

// TODO: Create methods containing your application logic.
[EnableClientAccess()]
public class SampleDomainService : DomainService
{
[Query]
public IQueryable<Folder> GetFolder()
{
var folder = new Folder() { ID = Guid.NewGuid(), Name = "Level 1 Folder" };
var subFolders = new[]{
new Folder(){ID=Guid.NewGuid(),Name="Level 2 Folder"},
new Folder(){ID=Guid.NewGuid(),Name="Level 2 Folder 2"}
};
folder.SubFolder = subFolders;
return new[] { folder }.AsQueryable();
}
}
}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

这个代码没有什么特别的,我们计划向客户端发送的结果是一个Folder,但同时它包含了两个子Folder。

编写上面两个类型很顺利，然后我们生成项目，因为使用了Domain Service，所以在Silverlight应用程序中会得到一个自动生成的类型

我们打开那个文件，确实里面是有一个Folder的类型

/// <summary>
/// The 'Folder' entity class.
/// </summary>
[DataContract(Namespace="http://schemas.datacontract.org/2004/07/DomainServiceSample.Web")]
public sealed partial class Folder : Entity
{

private Guid _id;

private string _name;

#region Extensibility Method Definitions

/// <summary>
/// This method is invoked from the constructor once initialization is complete and
/// can be used for further object setup.
/// </summary>
partial void OnCreated();
partial void OnIDChanging(Guid value);
partial void OnIDChanged();
partial void OnNameChanging(string value);
partial void OnNameChanged();

#endregion

/// <summary>
/// Initializes a new instance of the <see cref="Folder"/> class.
/// </summary>
public Folder()
{
this.OnCreated();
}

/// <summary>
/// Gets or sets the 'ID' value.
/// </summary>
[DataMember()]
[Editable(false, AllowInitialValue=true)]
[Key()]
[RoundtripOriginal()]
public Guid ID
{
get
{
return this._id;
}
set
{
if ((this._id != value))
{
this.OnIDChanging(value);
this.ValidateProperty("ID", value);
this._id = value;
this.RaisePropertyChanged("ID");
this.OnIDChanged();
}
}
}

/// <summary>
/// Gets or sets the 'Name' value.
/// </summary>
[DataMember()]
public string Name
{
get
{
return this._name;
}
set
{
if ((this._name != value))
{
this.OnNameChanging(value);
this.RaiseDataMemberChanging("Name");
this.ValidateProperty("Name", value);
this._name = value;
this.RaiseDataMemberChanged("Name");
this.OnNameChanged();
}
}
}

/// <summary>
/// Computes a value from the key fields that uniquely identifies this entity instance.
/// </summary>
/// <returns>An object instance that uniquely identifies this entity instance.</returns>
public override object GetIdentity()
{
return this._id;
}
}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

但是，让人疑惑的是，这个类型里面并没有包含SubFolder这个属性

这是什么情况呢？难道RIA Service不允许传递这种包含递归类型引用的实体？确实如此。

我目前的解决方法是：

1. 为Folder类型添加一个ParentID属性

2. 为SubFolder设置关联，即子Folder的ParentID设置到父Folder的ID。并且定义他们的关联

3. 使用Include属性标记SubFolder是要包含进来的

所以，这个类型修改为下面这样

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;

using System.Runtime.Serialization;
using System.ComponentModel.DataAnnotations;

using System.ServiceModel.DomainServices.Server;

namespace DomainServiceSample.Web
{
[DataContract]//必须声明类别为DataContract
public class Folder
{
[DataMember]//必须声明属性为DataMember
[Key]//一个用于DomainService的Entity必须有一个Key
public Guid ID { get; set; }

[DataMember]
public string Name { get; set; }

[DataMember]
[Association("Test","ID","ParentID")]
[Include]
public Folder[] SubFolder { get; set; }

[DataMember]
public Guid ParentID { get; set; }

}
}

然后，我们再来看在Silverlight中生成的那个类型

/// <summary>
/// The 'Folder' entity class.
/// </summary>
[DataContract(Namespace="http://schemas.datacontract.org/2004/07/DomainServiceSample.Web")]
public sealed partial class Folder : Entity
{

private Guid _id;

private string _name;

private Guid _parentID;

private EntityCollection<Folder> _subFolder;

#region Extensibility Method Definitions

/// <summary>
/// This method is invoked from the constructor once initialization is complete and
/// can be used for further object setup.
/// </summary>
partial void OnCreated();
partial void OnIDChanging(Guid value);
partial void OnIDChanged();
partial void OnNameChanging(string value);
partial void OnNameChanged();
partial void OnParentIDChanging(Guid value);
partial void OnParentIDChanged();

#endregion

/// <summary>
/// Initializes a new instance of the <see cref="Folder"/> class.
/// </summary>
public Folder()
{
this.OnCreated();
}

/// <summary>
/// Gets or sets the 'ID' value.
/// </summary>
[DataMember()]
[Editable(false, AllowInitialValue=true)]
[Key()]
[RoundtripOriginal()]
public Guid ID
{
get
{
return this._id;
}
set
{
if ((this._id != value))
{
this.OnIDChanging(value);
this.ValidateProperty("ID", value);
this._id = value;
this.RaisePropertyChanged("ID");
this.OnIDChanged();
}
}
}

/// <summary>
/// Gets or sets the 'Name' value.
/// </summary>
[DataMember()]
public string Name
{
get
{
return this._name;
}
set
{
if ((this._name != value))
{
this.OnNameChanging(value);
this.RaiseDataMemberChanging("Name");
this.ValidateProperty("Name", value);
this._name = value;
this.RaiseDataMemberChanged("Name");
this.OnNameChanged();
}
}
}

/// <summary>
/// Gets or sets the 'ParentID' value.
/// </summary>
[DataMember()]
public Guid ParentID
{
get
{
return this._parentID;
}
set
{
if ((this._parentID != value))
{
this.OnParentIDChanging(value);
this.RaiseDataMemberChanging("ParentID");
this.ValidateProperty("ParentID", value);
this._parentID = value;
this.RaiseDataMemberChanged("ParentID");
this.OnParentIDChanged();
}
}
}

/// <summary>
/// Gets the collection of associated <see cref="Folder"/> entity instances.
/// </summary>
[Association("Test", "ID", "ParentID")]
public EntityCollection<Folder> SubFolder
{
get
{
if ((this._subFolder == null))
{
this._subFolder = new EntityCollection<Folder>(this, "SubFolder", this.FilterSubFolder);
}
return this._subFolder;
}
}

private bool FilterSubFolder(Folder entity)
{
return (entity.ParentID == this.ID);
}

/// <summary>
/// Computes a value from the key fields that uniquely identifies this entity instance.
/// </summary>
/// <returns>An object instance that uniquely identifies this entity instance.</returns>
public override object GetIdentity()
{
return this._id;
}
}

<UserControl x:Class="DomainServiceSample.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
d:DesignHeight="300" d:DesignWidth="400" xmlns:sdk="http://schemas.microsoft.com/winfx/2006/xaml/presentation/sdk">

<Grid x:Name="LayoutRoot" Background="White">
<sdk:DataGrid AutoGenerateColumns="True" Margin="16,13,12,12" Name="dataGrid1" ItemsSource="{Binding}" RowDetailsVisibilityMode="Visible">
<sdk:DataGrid.RowDetailsTemplate>
<DataTemplate>
<sdk:DataGrid AutoGenerateColumns="True" Margin="20,20,20,20" Height="300" ItemsSource="{Binding SubFolder}" />
</DataTemplate>
</sdk:DataGrid.RowDetailsTemplate>
</sdk:DataGrid>
</Grid>
</UserControl>

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using DomainServiceSample.Web;

namespace DomainServiceSample
{
public partial class MainPage : UserControl
{
public MainPage()
{
InitializeComponent();

Loaded += new RoutedEventHandler(MainPage_Loaded);
}

void MainPage_Loaded(object sender, RoutedEventArgs e)
{
var ctx = new SampleDomainContext();
var op = ctx.Load<Folder>(ctx.GetFolderQuery());
dataGrid1.DataContext = op.Entities;
}
}
}

同时，服务端的代码我也稍作了修改

namespace DomainServiceSample.Web
{
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Linq;
using System.ServiceModel.DomainServices.Hosting;
using System.ServiceModel.DomainServices.Server;

// TODO: Create methods containing your application logic.
[EnableClientAccess()]
public class SampleDomainService : DomainService
{
[Query]
public IQueryable<Folder> GetFolder()
{
var folder = new Folder() { ID = Guid.NewGuid(), Name = "Level 1 Folder" };
var subFolders = new[]{
new Folder(){ID=Guid.NewGuid(),Name="Level 2 Folder",ParentID=folder.ID},
new Folder(){ID=Guid.NewGuid(),Name="Level 2 Folder 2",ParentID=folder.ID}
};
folder.SubFolder = subFolders;
return new[] { folder }.AsQueryable();
}
}
}

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

.csharpcode, .csharpcode pre
{
font-size: small;
color: black;
font-family: consolas, "Courier New", courier, monospace;
background-color: #ffffff;
/*white-space: pre;*/
}
.csharpcode pre { margin: 0em; }
.csharpcode .rem { color: #008000; }
.csharpcode .kwrd { color: #0000ff; }
.csharpcode .str { color: #006080; }
.csharpcode .op { color: #0000c0; }
.csharpcode .preproc { color: #cc6633; }
.csharpcode .asp { background-color: #ffff00; }
.csharpcode .html { color: #800000; }
.csharpcode .attr { color: #ff0000; }
.csharpcode .alt
{
background-color: #f4f4f4;
width: 100%;
margin: 0em;
}
.csharpcode .lnum { color: #606060; }

调试起来看到的效果如下

虽然解决了问题，但个人感觉Domain Service这个设计值得商榷。如果各位有更好的见解和解决方案，请不吝赐教

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