以下のコードを参照してください。
Private Sub TransactionExample3()
Dim objDR As SqlDataReader
Dim objCommand As SqlCommand, objCommand2 As SqlCommand
Dim objCon As SqlConnection
Dim objCon2 As SqlConnection
Dim id As Integer
Dim list As List(Of Integer) = New List(Of Integer)
Try
_ConString = "Data Source=databaseserver;Initial Catalog=Person;User ID=username;Password=password;MultipleActiveResultSets=True"
list.Add(1)
list.Add(2)
list.Add(3)
For Each i As Integer In list
Using trans = New TransactionScope()
objCon2 = New SqlConnection(_ConString)
objCon2.Open()
objCommand2 = New SqlCommand()
objCommand2.Connection = objCon2
Using objCon2
objCommand2.CommandText = "UPDATE Person SET forenames = @forenames WHERE " & _
" Reference = @Reference "
objCommand2.Parameters.AddWithValue("@forenames", i + 1)
objCommand2.Parameters.AddWithValue("@Reference", i)
objCommand2.ExecuteNonQuery()
objCommand2.Parameters.Clear()
End Using
trans.Complete()
End Using
Next
Catch ex As Exception
Throw
Finally
End Try
End Sub
このコードは機能します。つまり、各ループで変更がデータベースにコミットされます。
以下のコードをご覧ください。
Private Sub TransactionExample3()
Dim objDR As SqlDataReader
Dim objCommand As SqlCommand, objCommand2 As SqlCommand
Dim objCon As SqlConnection
Dim objCon2 As SqlConnection
Dim id As Integer
Try
_ConString = "Data Source=server;Initial Catalog=Person;User ID=Username;Password=Password;MultipleActiveResultSets=True"
objCon = New SqlConnection(_ConString)
objCommand = New SqlCommand("SELECT top 10 * from Person")
objCommand.Connection = objCon
objCon.Open()
objDR = objCommand.ExecuteReader()
Do While objDR.Read
objCon2 = New SqlConnection(_ConString)
objCon2.Open()
Using trans = New TransactionScope()
objCommand2 = New SqlCommand()
objCommand2.Connection = objCon
Using objCon2
objCommand2.CommandText = "UPDATE Person SET forenames = @forenames WHERE " & _
" Reference = @Reference "
objCommand2.Parameters.AddWithValue("@forenames", objDR("Reference") + 10)
objCommand2.Parameters.AddWithValue("@Reference", objDR("Reference"))
objCommand2.ExecuteNonQuery()
objCommand2.Parameters.Clear()
End Using
End Using
Loop
objDR.Close() 'line 16
Catch ex As Exception
Throw
Finally
End Try
End Sub
2 番目のコードの抜粋では、スコープは完全ではありません (scope.complete) が、while ループの反復ごとに結果がデータベースにコミットされます。どうしてこれなの?