HOW TO：從物件內容手動開啟連接 (Entity Framework)

本主題提供的範例將示範如何從物件內容手動開啟連接。 如需詳細資訊，請參閱管理物件內容 (Entity Framework)。

本主題的範例是根據 AdventureWorks Sales Model (EDM)。 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 Entity Data Model 精靈 (Entity Framework) 中的程序。

範例

此範例會手動開啟連接，然後執行查詢及儲存變更。 當內容超出範圍且遭到處置時，就會關閉連接。

' Define the order ID for the order we want.
Dim orderId As Integer = 43661

Using advWorksContext As New AdventureWorksEntities()
    Try
        ' Explicitly open the connection.
        advWorksContext.Connection.Open()

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

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

        ' Save changes.
        If 0 < advWorksContext.SaveChanges() Then
        Console.WriteLine("Changes saved.")
        End If
    Catch ex As InvalidOperationException
        Console.WriteLine(ex.ToString())
    End Try
    ' The connection is closed when the object context
    ' is disposed because it is no longer in scope.
End Using

// Define the order ID for the order we want.
int orderId = 43661;

using (AdventureWorksEntities advWorksContext =
    new AdventureWorksEntities())
{
    try
    {
        // Explicitly open the connection.    
        advWorksContext.Connection.Open();

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


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

        // Save changes.
        if (0 < advWorksContext.SaveChanges())
        {
            Console.WriteLine("Changes saved.");
        }
    }
    catch (InvalidOperationException ex)
    {
        Console.WriteLine(ex.ToString());
    }

    // The connection is closed when the object context
    // is disposed because it is no longer in scope.
}

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