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)