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HOW TO:使用 EntityConnection 搭配物件內容 (Entity Framework)

本主題提供的範例將示範如何提供現有的 EntityConnection 給即將使用的物件內容。 如需詳細資訊,請參閱Managing the Object Context (Entity Framework)

本主題的範例是根據 AdventureWorks 銷售模型。 若要執行此範例中的程式碼,您必須已經將 AdventureWorks Sales Model 加入到專案中,並設定您的專案使用 Entity Framework。 若要這樣做,請完成 HOW TO:使用實體資料模型精靈 (Entity Framework) 中的程序。

範例

這個範例會建立 EntityConnection,然後將它傳遞至長時間執行之 ObjectContext 的建構函式 (Constructor) 中。 連接已手動開啟。 EntityConnectionObjectContext 則已手動處置 (Dispose)。

' Define the order ID for the order we want. 
Dim orderId As Integer = 43680

' Create an EntityConnection. 
Dim conn As New EntityConnection("name=AdventureWorksEntities")

' Create a long-running context with the connection. 
Dim context As New AdventureWorksEntities(conn)

Try
    ' Explicitly open the connection. 
    If conn.State <> ConnectionState.Open Then
        conn.Open()
    End If

    ' Execute a query to return an order. 
    Dim order As SalesOrderHeader = context.SalesOrderHeaders.Where("it.SalesOrderID = @orderId", _
                                        New ObjectParameter("orderId", orderId)).Execute(MergeOption.AppendOnly).First()

    ' Change the status of the order. 
    order.Status = 1

    ' You do not have to call the Load method to load the details for the order, 
    ' because lazy loading is set to true 
    ' by the constructor of the AdventureWorksEntities object. 
    ' With lazy loading set to true the related objects are loaded when 
    ' you access the navigation property. In this case SalesOrderDetails. 

    ' Delete the first item in the order. 
    context.DeleteObject(order.SalesOrderDetails.First())

    ' Save changes. 
    If 0 < context.SaveChanges() Then
        Console.WriteLine("Changes saved.")
    End If

    ' Create a new SalesOrderDetail object. 
    ' You can use the static CreateObjectName method (the Entity Framework 
    ' adds this method to the generated entity types) instead of the new operator: 
    ' SalesOrderDetail.CreateSalesOrderDetail(1, 0, 2, 750, 1, (decimal)2171.2942, 0, 0, 
    ' Guid.NewGuid(), DateTime.Today)); 
    Dim detail = New SalesOrderDetail With
    {
        .SalesOrderID = 0,
        .SalesOrderDetailID = 0,
        .OrderQty = 2,
        .ProductID = 750,
        .SpecialOfferID = 1,
        .UnitPrice = CDec(2171.2942),
        .UnitPriceDiscount = 0,
        .LineTotal = 0,
        .rowguid = Guid.NewGuid(),
        .ModifiedDate = DateTime.Now
    }

    order.SalesOrderDetails.Add(detail)

    ' Save changes again. 
    If 0 < context.SaveChanges() Then
        Console.WriteLine("Changes saved.")
    End If
Catch ex As InvalidOperationException
    Console.WriteLine(ex.ToString())
Finally
    ' Explicitly dispose of the context and the connection. 
    context.Dispose()
    conn.Dispose()
// Define the order ID for the order we want.
int orderId = 43680;

// Create an EntityConnection.
EntityConnection conn =
    new EntityConnection("name=AdventureWorksEntities");

// Create a long-running context with the connection.
AdventureWorksEntities context =
    new AdventureWorksEntities(conn);

try
{
    // Explicitly open the connection.
    if (conn.State != ConnectionState.Open)
    {
        conn.Open();
    }

    // Execute a query to return an order.
    SalesOrderHeader order =
        context.SalesOrderHeaders.Where(
        "it.SalesOrderID = @orderId", new ObjectParameter("orderId", orderId))
        .Execute(MergeOption.AppendOnly).First();

    // Change the status of the order.
    order.Status = 1;

    // You do not have to call the Load method to load the details for the order,
    // because  lazy loading is set to true 
    // by the constructor of the AdventureWorksEntities object. 
    // With  lazy loading set to true the related objects are loaded when
    // you access the navigation property. In this case SalesOrderDetails.

    // Delete the first item in the order.
    context.DeleteObject(order.SalesOrderDetails.First());

    // Save changes.
    if (0 < context.SaveChanges())
    {
        Console.WriteLine("Changes saved.");
    }

    // Create a new SalesOrderDetail object.
    // You can use the static CreateObjectName method (the Entity Framework
    // adds this method to the generated entity types) instead of the new operator:
    // SalesOrderDetail.CreateSalesOrderDetail(1, 0, 2, 750, 1, (decimal)2171.2942, 0, 0,
    //                                         Guid.NewGuid(), DateTime.Today));
    SalesOrderDetail detail = new SalesOrderDetail
    {
        SalesOrderID = 1,
        SalesOrderDetailID = 0,
        OrderQty = 2,
        ProductID = 750,
        SpecialOfferID = 1,
        UnitPrice = (decimal)2171.2942,
        UnitPriceDiscount = 0,
        LineTotal = 0,
        rowguid = Guid.NewGuid(),
        ModifiedDate = DateTime.Now
    };

    order.SalesOrderDetails.Add(detail);

    // Save changes again.
    if (0 < context.SaveChanges())
    {
        Console.WriteLine("Changes saved.");
    }
}
catch (InvalidOperationException ex)
{
    Console.WriteLine(ex.ToString());
}
finally
{
    // Explicitly dispose of the context and the connection. 
    context.Dispose();
    conn.Dispose();
}

另請參閱

工作

HOW TO:在長時間執行的物件內容中管理連接 (Entity Framework)
HOW TO:從物件內容手動開啟連接 (Entity Framework)