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How to: Create a Data Service Using a LINQ to SQL Data Source (WCF Data Services)

WCF Data Services exposes entity data as a data service. The reflection provider enables you to define a data model that is based on any class that exposes members that return an IQueryable implementation. To be able to make updates to data in the data source, these classes must also implement the IUpdatable interface. For more information, see Data Services Providers (WCF Data Services). This topic shows you how to create LINQ to SQL classes that access the Northwind sample database by using the reflection provider, as well as how to create the data service that is based on these data classes.

To add LINQ to SQL classes to a project

  1. From within a Visual Basic or C# application, on the Project menu, click Add New Item.

  2. Click the LINQ to SQL Classes template.

  3. Change the name to Northwind.dbml.

  4. Click Add.

    The Northwind.dbml file is added to the project and the Object Relational Designer (O/R Designer) opens.

  5. In Server/Database Explorer, under Northwind, expand Tables and drag the Customers table onto the Object Relational Designer (O/R Designer).

    A Customer entity class is created and appears on the design surface.

  6. Repeat step 6 for the Orders, Order_Details, and Products tables.

  7. Right-click the new .dbml file that represents the LINQ to SQL classes and click View Code.

    This creates a new code-behind page named Northwind.cs that contains a partial class definition for the class that inherits from the DataContext class, which in this case is NorthwindDataContext.

  8. Replace the contents of the Northwind.cs code file with the following code. This code implements the reflection provider by extending the DataContext and data classes generated by LINQ to SQL:

    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
    
    

To create a data service by using a LINQ to SQL-based data model

  1. In Solution Explorer, right-click the name of your ASP.NET project, and then click Add New Item.

  2. In the Add New Item dialog box, select WCF Data Service.

  3. Supply a name for the service, and then click OK.

    Visual Studio creates the XML markup and code files for the new service. By default, the code-editor window opens.

  4. In the code for the data service, replace the comment /* TODO: put your data source class name here */ in the definition of the class that defines the data service with the type that is the entity container of the data model, which in this case is NorthwindDataContext.

  5. In the code for the data service, replace the placeholder code in the InitializeService function with the following:

    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)
    
    

    This enables authorized clients to access resources for the three specified entity sets.

  6. To test the Northwind.svc data service by using a Web browser, follow the instructions in the topic Accessing the Service from a Web Browser (WCF Data Services Quickstart).

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