方法: Entity Framework のトランザクションを管理する
このトピックでは、オブジェクト コンテキスト内のオブジェクトに対する変更を、他の外部の処理との間で調整するトランザクションの定義方法について説明します。 詳細については、「接続とトランザクションの管理 (Entity Framework)」を参照してください。
このトピックの例には、AdventureWorks Sales Model が使用されています。 To run the code in this example, you must have already added the AdventureWorks Sales Model to your project and configured your project to use the Entity Framework. 具体的な方法については、「Entity Data Model ウィザードを使用する方法 (Entity Framework)」の手順を参照してください。 Microsoft Windows メッセージ キューもインストールしておく必要があります。
例
この例には、TransactionScope が定義されています。 TransactionScope を定義することにより、オブジェクト コンテキスト内のオブジェクトに対する変更がメッセージ キューを使って調整されます。 Entity Framework では、変更をデータベースに保存する際にこのトランザクションを使用します。 UpdateException が発生した場合は、操作が 2 回まで再試行されます。 処理が成功した場合は、オブジェクト コンテキストでの変更が受け入れられます。 詳細については、「接続とトランザクションの管理 (Entity Framework)」を参照してください。
この例では、実行時間の長いオブジェクト コンテキストを使用しています。オブジェクト コンテキストは、トランザクションが成功するか、すべての再試行を終えた後に破棄されます。
Imports System
Imports System.Linq
Imports System.Data
Imports System.Data.Objects
Imports System.Messaging
Imports System.Transactions
Class TransactionSample
Public Shared Sub EnlistTransaction()
Dim retries As Integer = 3
Dim queueName As String = ".\Fulfilling"
' Define variables that we need to add an item.
Dim quantity As Short = 2
Dim productId As Integer = 750
Dim orderId As Integer = 43680
' Define a long-running object context.
Dim context As New AdventureWorksEntities()
Dim success As Boolean = False
' Wrap the operation in a retry loop.
For i As Integer = 0 To retries - 1
' Define a transaction scope for the operations.
Using transaction As New TransactionScope()
Try
' Define a query that returns a order by order ID.
Dim order = (From o In context.SalesOrderHeaders _
Where o.SalesOrderID = orderId _
Select o).First()
' Load items for the order, if not already loaded.
' Do this if the lazy loading is turned off.
If Not order.SalesOrderDetails.IsLoaded Then
order.SalesOrderDetails.Load()
End If
' Load the customer, if not already loaded.
' Do this if the lazy loading is turned off.
If Not order.ContactReference.IsLoaded Then
order.ContactReference.Load()
End If
' Create a new item for an existing order.
Dim newItem As SalesOrderDetail = SalesOrderDetail.CreateSalesOrderDetail(0, 0, quantity, productId, 1, 0, _
0, 0, Guid.NewGuid(), DateTime.Today)
' Add new item to the order.
order.SalesOrderDetails.Add(newItem)
' Save changes pessimistically. This means that changes
' must be accepted manually once the transaction succeeds.
context.SaveChanges(SaveOptions.DetectChangesBeforeSave)
' Create the message queue if it does not already exist.
If Not MessageQueue.Exists(queueName) Then
MessageQueue.Create(queueName)
End If
' Initiate fulfilling order by sending a message.
Using q As New MessageQueue(queueName)
Dim msg As New System.Messaging.Message([String].Format("<order customerId='{0}'>" & "<orderLine product='{1}' quantity='{2}' />" & "</order>", order.Contact.ContactID, newItem.ProductID, newItem.OrderQty))
' Send the message to the queue.
q.Send(msg)
End Using
' Mark the transaction as complete.
transaction.Complete()
success = True
Exit Try
Catch ex As Exception
' Handle errors and deadlocks here and retry if needed.
' Allow an UpdateException to pass through and
' retry, otherwise stop the execution.
If ex.[GetType]() <> GetType(UpdateException) Then
Console.WriteLine(("An error occured. " & "The operation cannot be retried.") + ex.Message)
Exit Try
' If we get to this point, the operation will be retried.
End If
End Try
End Using
Next
If success Then
' Reset the context since the operation succeeded.
context.AcceptAllChanges()
Else
Console.WriteLine("The operation could not be completed in " & retries & " tries.")
End If
' Dispose the object context.
context.Dispose()
End Sub
End Class
using System;
using System.Linq;
using System.Data;
using System.Data.Objects;
using System.Messaging;
using System.Transactions;
namespace ObjectServicesConceptsCS
{
class TransactionSample
{
public static void EnlistTransaction()
{
int retries = 3;
string queueName = @".\Fulfilling";
// Define variables that we need to add an item.
short quantity = 2;
int productId = 750;
int orderId = 43680;
// Define a long-running object context.
AdventureWorksEntities context
= new AdventureWorksEntities();
bool success = false;
// Wrap the operation in a retry loop.
for (int i = 0; i < retries; i++)
{
// Define a transaction scope for the operations.
using (TransactionScope transaction = new TransactionScope())
{
try
{
// Define a query that returns a order by order ID.
SalesOrderHeader order =
context.SalesOrderHeaders.Where
("it.SalesOrderID = @id", new ObjectParameter(
"id", orderId)).First();
// Load items for the order, if not already loaded.
if (!order.SalesOrderDetails.IsLoaded)
{
order.SalesOrderDetails.Load();
}
// Load the customer, if not already loaded.
if (!order.ContactReference.IsLoaded)
{
order.ContactReference.Load();
}
// Create a new item for an existing order.
SalesOrderDetail newItem = SalesOrderDetail.CreateSalesOrderDetail(
0, 0, quantity, productId, 1, 0, 0, 0, Guid.NewGuid(), DateTime.Today);
// Add new item to the order.
order.SalesOrderDetails.Add(newItem);
// Save changes pessimistically. This means that changes
// must be accepted manually once the transaction succeeds.
context.SaveChanges(SaveOptions.DetectChangesBeforeSave);
// Create the message queue if it does not already exist.
if (!MessageQueue.Exists(queueName))
{
MessageQueue.Create(queueName);
}
// Initiate fulfilling order by sending a message.
using (MessageQueue q = new MessageQueue(queueName))
{
System.Messaging.Message msg =
new System.Messaging.Message(String.Format(
"<order customerId='{0}'>" +
"<orderLine product='{1}' quantity='{2}' />" +
"</order>", order.Contact.ContactID,
newItem.ProductID, newItem.OrderQty));
// Send the message to the queue.
q.Send(msg);
}
// Mark the transaction as complete.
transaction.Complete();
success = true;
break;
}
catch (Exception ex)
{
// Handle errors and deadlocks here and retry if needed.
// Allow an UpdateException to pass through and
// retry, otherwise stop the execution.
if (ex.GetType() != typeof(UpdateException))
{
Console.WriteLine("An error occured. "
+ "The operation cannot be retried."
+ ex.Message);
break;
}
// If we get to this point, the operation will be retried.
}
}
}
if (success)
{
// Reset the context since the operation succeeded.
context.AcceptAllChanges();
}
else
{
Console.WriteLine("The operation could not be completed in "
+ retries + " tries.");
}
// Dispose the object context.
context.Dispose();
}
}
}