HOW TO：明確載入 POCO 實體 (Entity Framework)

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02/28/2011

本主題中的範例為您示範如何使用 ObjectContext 上的 LoadProperty 方法來明確載入相關物件。如需使用消極式載入來存取相關物件的範例，請參閱 HOW TO：使用消極式載入來載入相關物件 (Entity Framework)。 LoadProperty 方法可以搭配 POCO 實體和衍生自 EntityObject 的實體使用。

本主題中的範例使用 HOW TO：定義 POCO 實體 (Entity Framework) 中所定義之 POCO 資料類別、在 HOW TO：定義自訂物件內容 (Entity Framework) 中建立的 AdventureWorksEntities 類別 (衍生自 ObjectContext)，以及 HOW TO：自訂模型與對應檔以搭配自訂物件運作 (Entity Framework) 中所定義之 AdventureWorks 架構資料模型。

範例

本範例會傳回前五個 Order 物件，並呼叫 LoadProperty 方法，來為每個 Order 明確載入相關的 LineItem 物件。

Using context As New POCOAdventureWorksEntities()
    Try
        ' Disable lazy loading. 
        context.ContextOptions.LazyLoadingEnabled = False

        ' Get the first five orders. 
        For Each order As Order In context.Orders.Take(5)
            ' Because LazyLoadingEnabled is set to false, 
            ' we need to explicitly load the related line items for the order. 
            context.LoadProperty(order, "LineItems")

            Console.WriteLine(String.Format("PO Number: {0}", order.ExtendedInfo.PurchaseOrderNumber))
            Console.WriteLine(String.Format("Order Date: {0}", order.OrderDate.ToString()))
            Console.WriteLine("Order items:")
            For Each item As LineItem In order.LineItems
                Console.WriteLine(String.Format("Product: {0} " & "Quantity: {1}", item.ProductID, item.OrderQty))
            Next
        Next
    Catch ex As InvalidOperationException
        Console.WriteLine(ex.Message)
    Catch ex As Exception
        Console.WriteLine(ex.Message)
    End Try
End Using

using (POCOAdventureWorksEntities context =
        new POCOAdventureWorksEntities())
{
    try
    {
        // Disable lazy loading.
        context.ContextOptions.LazyLoadingEnabled = false;

        // Get the first five orders.
        foreach (Order order in context.Orders.Take(5))
        {
            // Because LazyLoadingEnabled is set to false,
            // we need to explicitly load the related line items for the order.
            context.LoadProperty(order, "LineItems");

            Console.WriteLine(String.Format("PO Number: {0}",
                order.ExtendedInfo.PurchaseOrderNumber));
            Console.WriteLine(String.Format("Order Date: {0}",
                order.OrderDate.ToString()));
            Console.WriteLine("Order items:");
            foreach (LineItem item in order.LineItems)
            {
                Console.WriteLine(String.Format("Product: {0} "
                    + "Quantity: {1}", item.ProductID,
                    item.OrderQty));
            }
        }
    }
    catch (InvalidOperationException ex)
    {
        Console.WriteLine(ex.Message);
    }
    catch (Exception ex)
    {
        Console.WriteLine(ex.Message);
    }
}

共用方式為

HOW TO：明確載入 POCO 實體 (Entity Framework)

範例

另請參閱

概念

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