RIA Service中对于递归实体类型处理的问题及解决方案

来源：互联网发布：brew install node 6 编辑：程序博客网时间：2024/06/07 02:00

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

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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 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();        }    }}

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

    ///     /// The 'Folder' entity class.    ///     [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        ///         /// This method is invoked from the constructor once initialization is complete and        /// can be used for further object setup.        ///         partial void OnCreated();        partial void OnIDChanging(Guid value);        partial void OnIDChanged();        partial void OnNameChanging(string value);        partial void OnNameChanged();        #endregion                        ///         /// Initializes a new instance of the  class.        ///         public Folder()        {            this.OnCreated();        }                ///         /// Gets or sets the 'ID' value.        ///         [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();                }            }        }                ///         /// Gets or sets the 'Name' value.        ///         [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();                }            }        }                ///         /// Computes a value from the key fields that uniquely identifies this entity instance.        ///         /// An object instance that uniquely identifies this entity instance.        public override object GetIdentity()        {            return this._id;        }    }

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

   ///     /// The 'Folder' entity class.    ///     [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 _subFolder;                #region Extensibility Method Definitions        ///         /// This method is invoked from the constructor once initialization is complete and        /// can be used for further object setup.        ///         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                        ///         /// Initializes a new instance of the  class.        ///         public Folder()        {            this.OnCreated();        }                ///         /// Gets or sets the 'ID' value.        ///         [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();                }            }        }                ///         /// Gets or sets the 'Name' value.        ///         [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();                }            }        }                ///         /// Gets or sets the 'ParentID' value.        ///         [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();                }            }        }                ///         /// Gets the collection of associated  entity instances.        ///         [Association("Test", "ID", "ParentID")]        public EntityCollection SubFolder        {            get            {                if ((this._subFolder == null))                {                    this._subFolder = new EntityCollection(this, "SubFolder", this.FilterSubFolder);                }                return this._subFolder;            }        }                private bool FilterSubFolder(Folder entity)        {            return (entity.ParentID == this.ID);        }                ///         /// Computes a value from the key fields that uniquely identifies this entity instance.        ///         /// An object instance that uniquely identifies this entity instance.        public override object GetIdentity()        {            return this._id;        }    }

这时就看到SubFolder了，而且还包含了很多其他的属性。

最后，我做了一个界面来显示给大家看看效果

MainPage.xaml的内容如下

<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>

MainPage.xaml.cs的内容如下

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(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 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();        }    }}

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