如何：使用 LINQ to SQL 数据源创建数据服务（WCF 数据服务）

项目
02/28/2011

WCF 数据服务将实体数据作为数据服务公开。使用反射提供程序可以定义基于以下任何类的数据模型：公开返回 IQueryable 实现的成员。为了能够更新数据源中的数据，这些类还必须实现 IUpdatable 接口。有关更多信息，请参见数据服务提供程序（WCF 数据服务）。本主题演示如何创建通过使用反射提供程序来访问 Northwind 示例数据库的 LINQ to SQL 类，以及如何创建基于这些数据类的数据服务。

向项目中添加 LINQ to SQL 类

在 Visual Basic 或 C# 应用程序中，从**“项目”菜单中单击“添加新项”**。
单击**“LINQ to SQL 类”**模板。
将名称更改为 Northwind.dbml。
单击**“添加”**。

此时，Northwind.dbml 文件将随即添加到项目中且对象关系设计器（O/R 设计器）将打开。
在**“服务器”/“数据库资源管理器”中，在“Northwind”下展开“表”**，再将 Customers 表拖到对象关系设计器（O/R 设计器）上。

此时将随即创建一个 Customer 实体类并显示在设计图面上。
对 Orders、Order_Details 和 Products 表重复步骤 6。
右击表示该 LINQ to SQL 类的新 .dbml 文件，再单击**“查看代码”**。

这将创建一个名为 Northwind.cs 的新代码隐藏页，其中包含从 DataContext 类（在此示例中为 NorthwindDataContext）继承的类的分部类定义。

用下列代码替换 Northwind.cs 代码文件的内容。此代码通过扩展 DataContext 以及 LINQ to SQL 生成的数据类来实现反射提供程序：

Imports System.ComponentModel
Imports System.Collections
Imports System.Linq
Imports System.Reflection
Imports System.Data.Linq
Imports System.Data.Linq.Mapping
Imports System.Data.Services
Imports System.Data.Services.Common

' Define the key properties for the LINQ to SQL data classes.
<DataServiceKeyAttribute("CustomerID")> _
Partial Public Class Customer
End Class
<DataServiceKeyAttribute("ProductID")> _
Partial Public Class Product
End Class
<DataServiceKeyAttribute("OrderID")> _
Partial Public Class Order
End Class
<DataServiceKeyAttribute("OrderID", "ProductID")> _
Partial Public Class Order_Detail
End Class
#Region "IUpdatable implementation"
' Define the IUpdatable implementation for LINQ to SQL.
Partial Public Class NorthwindDataContext
    Implements IUpdatable
    ' Creates an object in the container.
    Function CreateResource(ByVal containerName As String, ByVal fullTypeName As String) _
        As Object Implements IUpdatable.CreateResource

        Dim t = Type.GetType(fullTypeName, True)
        Dim table = GetTable(t)
        Dim resource = Activator.CreateInstance(t)
        table.InsertOnSubmit(resource)
        Return resource
    End Function
    ' Gets the object referenced by the resource.
    Function GetResource(ByVal query As IQueryable, ByVal fullTypeName As String) As Object _
     Implements IUpdatable.GetResource
        Dim resource = query.Cast(Of Object)().SingleOrDefault()

        ' fullTypeName can be null for deletes
        If fullTypeName IsNot Nothing AndAlso resource.GetType().FullName <> fullTypeName Then
            Throw New ApplicationException("Unexpected type for this resource.")
        End If
        Return resource
    End Function
    ' Resets the value of the object to its default value.
    Function ResetResource(ByVal resource As Object) As Object _
        Implements IUpdatable.ResetResource
        Dim t = resource.GetType()
        Dim table = Mapping.GetTable(t)
        Dim dummyResource = Activator.CreateInstance(t)
        For Each member In table.RowType.DataMembers

            If Not member.IsPrimaryKey AndAlso Not member.IsDeferred AndAlso _
                Not member.IsAssociation AndAlso Not member.IsDbGenerated Then
                Dim defaultValue = member.MemberAccessor.GetBoxedValue(dummyResource)
                member.MemberAccessor.SetBoxedValue(resource, defaultValue)
            End If
            Next
        Return resource
    End Function
    ' Sets the value of the given property on the object.
    Sub SetValue(ByVal targetResource As Object, ByVal propertyName As String, _
                 ByVal propertyValue As Object) Implements IUpdatable.SetValue
        Dim table = Mapping.GetTable(targetResource.GetType())
        Dim member = table.RowType.DataMembers.Single(Function(x) x.Name = propertyName)
        member.MemberAccessor.SetBoxedValue(targetResource, propertyValue)
    End Sub
    ' Gets the value of a property on an object.
    Function GetValue(ByVal targetResource As Object, ByVal propertyName As String) _
    As Object Implements IUpdatable.GetValue
        Dim table = Mapping.GetTable(targetResource.GetType())
        Dim member = _
        table.RowType.DataMembers.Single(Function(x) x.Name = propertyName)
        Return member.MemberAccessor.GetBoxedValue(targetResource)
    End Function
    ' Sets the related object for a reference.
    Sub SetReference(ByVal targetResource As Object, ByVal propertyName As String, _
                     ByVal propertyValue As Object) Implements IUpdatable.SetReference
        CType(Me, IUpdatable).SetValue(targetResource, propertyName, propertyValue)
    End Sub
' Adds the object to the related objects collection.
    Sub AddReferenceToCollection(ByVal targetResource As Object, ByVal propertyName As String, _
                                 ByVal resourceToBeAdded As Object) _
                                 Implements IUpdatable.AddReferenceToCollection
        Dim pi = targetResource.GetType().GetProperty(propertyName)
        If pi Is Nothing Then
            Throw New Exception("Can't find property")
        End If
        Dim collection = CType(pi.GetValue(targetResource, Nothing), IList)
        collection.Add(resourceToBeAdded)
    End Sub
    ' Removes the object from the related objects collection.
    Sub RemoveReferenceFromCollection(ByVal targetResource As Object, ByVal propertyName As String, _
                                      ByVal resourceToBeRemoved As Object) _
                                      Implements IUpdatable.RemoveReferenceFromCollection
        Dim pi = targetResource.GetType().GetProperty(propertyName)
        If pi Is Nothing Then
            Throw New Exception("Can't find property")
        End If
        Dim collection = CType(pi.GetValue(targetResource, Nothing), IList)
        collection.Remove(resourceToBeRemoved)
    End Sub
        ' Deletes the resource.
    Sub DeleteResource(ByVal targetResource As Object) _
    Implements IUpdatable.DeleteResource
        Dim table = GetTable(targetResource.GetType())
        table.DeleteOnSubmit(targetResource)
    End Sub
    ' Saves all the pending changes.
    Sub SaveChanges() Implements IUpdatable.SaveChanges
        SubmitChanges()
    End Sub
    ' Returns the actual instance of the resource represented 
    ' by the resource object.
    Function ResolveResource(ByVal resource As Object) As Object Implements IUpdatable.ResolveResource
        Return resource
    End Function
        ' Reverts all the pending changes.
    Sub ClearChanges() Implements IUpdatable.ClearChanges
        ' Raise an exception as there is no real way to do this with LINQ to SQL.
        ' Comment out the following line if you'd prefer a silent failure
        Throw New NotSupportedException()
    End Sub
End Class
#End Region

using System;
using System.ComponentModel;
using System.Collections;
using System.Linq;
using System.Reflection;
using System.Data.Linq;
using System.Data.Linq.Mapping;
using System.Data.Services;
using System.Data.Services.Common;

namespace NorthwindService
{
    // Define the key properties for the LINQ to SQL data classes.
    [DataServiceKeyAttribute("CustomerID")]
    public partial class Customer { }

    [DataServiceKeyAttribute("ProductID")]
    public partial class Product { }

    [DataServiceKeyAttribute("OrderID")]
    public partial class Order { }

    [DataServiceKeyAttribute("OrderID", "ProductID")]
    public partial class Order_Detail { }

    #region IUpdatable implementation
    // Define the IUpdatable implementation for LINQ to SQL.
    public partial class NorthwindDataContext : IUpdatable
    {
        // Creates an object in the container.
        object IUpdatable.CreateResource(string containerName, string fullTypeName)
        {
            Type t = Type.GetType(fullTypeName, true);
            ITable table = GetTable(t);
            object resource = Activator.CreateInstance(t);
            table.InsertOnSubmit(resource);
            return resource;
        }

        // Gets the object referenced by the resource.
        object IUpdatable.GetResource(IQueryable query, string fullTypeName)
        {
            object resource = query.Cast<object>().SingleOrDefault();

            // fullTypeName can be null for deletes
            if (fullTypeName != null && resource.GetType().FullName != fullTypeName)
                throw new ApplicationException("Unexpected type for this resource.");
            return resource;
        }


        // Resets the value of the object to its default value.
        object IUpdatable.ResetResource(object resource)
        {
            Type t = resource.GetType();
            MetaTable table = Mapping.GetTable(t);
            object dummyResource = Activator.CreateInstance(t);
            foreach (var member in table.RowType.DataMembers)
            {
                if (!member.IsPrimaryKey && !member.IsDeferred &&
                    !member.IsAssociation && !member.IsDbGenerated)
                {
                    object defaultValue = member.MemberAccessor.GetBoxedValue(dummyResource);
                    member.MemberAccessor.SetBoxedValue(ref resource, defaultValue);
                }
            }
            return resource;
        }

        // Sets the value of the given property on the object.
        void IUpdatable.SetValue(object targetResource, string propertyName, object propertyValue)
        {
            MetaTable table = Mapping.GetTable(targetResource.GetType());
            MetaDataMember member = table.RowType.DataMembers.Single(x => x.Name == propertyName);
            member.MemberAccessor.SetBoxedValue(ref targetResource, propertyValue);
        }

        // Gets the value of a property on an object.
        object IUpdatable.GetValue(object targetResource, string propertyName)
        {
            MetaTable table = Mapping.GetTable(targetResource.GetType());
            MetaDataMember member =
                table.RowType.DataMembers.Single(x => x.Name == propertyName);
            return member.MemberAccessor.GetBoxedValue(targetResource);
        }

        // Sets the related object for a reference.
        void IUpdatable.SetReference(
            object targetResource, string propertyName, object propertyValue)
        {
            ((IUpdatable)this).SetValue(targetResource, propertyName, propertyValue);
        }

        // Adds the object to the related objects collection.
        void IUpdatable.AddReferenceToCollection(
            object targetResource, string propertyName, object resourceToBeAdded)
        {
            PropertyInfo pi = targetResource.GetType().GetProperty(propertyName);
            if (pi == null)
                throw new Exception("Can't find property");
            IList collection = (IList)pi.GetValue(targetResource, null);
            collection.Add(resourceToBeAdded);
        }

        // Removes the object from the related objects collection.
        void IUpdatable.RemoveReferenceFromCollection(
            object targetResource, string propertyName, object resourceToBeRemoved)
        {
            PropertyInfo pi = targetResource.GetType().GetProperty(propertyName);
            if (pi == null)
                throw new Exception("Can't find property");
            IList collection = (IList)pi.GetValue(targetResource, null);
            collection.Remove(resourceToBeRemoved);
        }

        // Deletes the resource.
        void IUpdatable.DeleteResource(object targetResource)
        {
            ITable table = GetTable(targetResource.GetType());
            table.DeleteOnSubmit(targetResource);
        }

        // Saves all the pending changes.
        void IUpdatable.SaveChanges()
        {
            SubmitChanges();
        }

        // Returns the actual instance of the resource represented 
        // by the resource object.
        object IUpdatable.ResolveResource(object resource)
        {
            return resource;
        }

        // Reverts all the pending changes.
        void IUpdatable.ClearChanges()
        {
            // Raise an exception as there is no real way to do this with LINQ to SQL.
            // Comment out the following line if you'd prefer a silent failure
            throw new NotSupportedException();
        }
    #endregion
    }
}

使用基于 LINQ to SQL 的数据模型创建数据服务

在**“解决方案资源管理器”中，右击 ASP.NET 项目的名称，然后单击“添加新项”**。
在**“添加新项”对话框中，选择“WCF 数据服务”**。
为该服务提供一个名称，然后单击**“确定”**。

Visual Studio 将为该新服务创建 XML 标记和代码文件。默认情况下，代码编辑器窗口将打开。
在数据服务的代码中，用数据模型的实体容器的类型（在此示例中为 NorthwindDataContext）替换定义数据服务的类定义中的注释 /* TODO: put your data source class name here */。

在数据服务的代码中，用下列代码替换 InitializeService 函数中的占位符代码：

config.SetEntitySetAccessRule("Customers", EntitySetRights.ReadMultiple)
config.SetEntitySetAccessRule("Orders", EntitySetRights.AllRead _
                            Or EntitySetRights.WriteMerge)
config.SetEntitySetAccessRule("Order_Details", EntitySetRights.AllRead _
                            Or EntitySetRights.AllWrite)
config.SetEntitySetAccessRule("Products", EntitySetRights.ReadMultiple)

config.SetEntitySetAccessRule("Customers", EntitySetRights.ReadMultiple);
config.SetEntitySetAccessRule("Orders", EntitySetRights.AllRead  
                            | EntitySetRights.WriteMerge);
config.SetEntitySetAccessRule("Order_Details", EntitySetRights.AllRead                             
                            | EntitySetRights.AllWrite);
config.SetEntitySetAccessRule("Products", EntitySetRights.ReadMultiple);

这使得授权客户端能够访问指定的三个实体集的资源。

若要使用 Web 浏览器测试 Northwind.svc 数据服务，请按照从 Web 浏览器访问服务（WCF 数据服务快速入门）主题中的说明操作。

另请参见

任务

如何：使用 ADO.NET 实体框架数据源创建数据服务（WCF 数据服务）
如何：使用反射提供程序创建数据服务（WCF 数据服务）

概念

数据服务提供程序（WCF 数据服务）

通过

如何：使用 LINQ to SQL 数据源创建数据服务（WCF 数据服务）

向项目中添加 LINQ to SQL 类

使用基于 LINQ to SQL 的数据模型创建数据服务

另请参见

任务

概念

其他资源