Using A Single Transaction With Multiple Typed DataSets
Provides a detailed explanation of how to implement a single transaction across multiple Typed Datasets
Introduction
If you have ever used Typed DataSets, you know how fast and easy they can make database access programming. The only drawback I ever ran into while using them is when I needed to put actions associated with several different Typed DataSets into a single Transaction
.
Background
Transactions and Typed DataSets are nothing new. However, when you want to place Updates to more than one database table through different Typed DataSets into a single transaction, things get a little more complicated. Hopefully, this article will help to explain that complexity and provide you with some generic class objects you can incorporate into your project with a few trivial modifications.
After searching the Web for hours and only finding a couple examples (which I couldn't get to work), I was forced to figure out my own way to accomplish this seemingly simple task. Let me tell you, the code you see here in this article took many hours to figure out and get working reliably. I am posting this article because there was so little information available on this topic on the Web that it seemed like an article on the topic would benefit the development community.
Using the Code
The Typed DataSet Extender Class
code shown in this article is added to each Typed DataSet's TableAdapter
class you want to be able to enlist in the Transaction
. The TableAdapter
's Partial Class
file is automatically created in Visual Studio 2005 by simply double-clicking on the Typed DataSet design surface. I believe you can also right click on Typed DataSet in the Solution Explorer and choose the "View Code" option.
Unfortunately, the Auto-Generated code does not create the NameSpace
or TableAdapter
's Partial Class
so you'll have to do that manually for each Typed DataSet you want to enlist in the Transaction
. The code shown below will be copied into each Typed DataSet's Partial Class
file created when you double-click on the Typed DataSet Design surface (the filename will be <TypedDataSetName>.vb).
Modifying the code below to extend your Typed DataSet classes is done by simply replacing the <TypedDataSetName>
tags (including the brackets < >
) in the class example shown below with the name of your Typed DataSet (the DataSet name without the XSD extension). You will need to copy the extender code below into every Typed DataSet class you want to use with a single Transaction
. You'll only need to change the <TypedDataSetName>
tags to match the name of the Typed DataSet, the rest of the code does not require any changes to work with your Typed DataSets.
Since this extender code is placed in a Partial Class
, it will not be lost when the Typed DataSet is modified or rebuilt so this effort only needs to be done once (and for any additional Typed DataSets you add to your project in the future). This is the power of the Partial Class
and is what makes it possible for you to have a Transaction
that spans across multiple Typed DataSets without invoking a Distributed Transaction
like using TransactionScope
does.
Here is the Typed DataSet NameSpace
code block you'll need to paste into each Typed DataSet's Partial Class
file:
Imports System.Data.SqlClient
Namespace <TypedDataSetName>TableAdapters
Partial Public Class <TypedDataSetName>Adapter
'Retrieves the return value from a Stored Procedure
Call Public Function GetReturnValue() As Integer
Return CInt(Me.Adapter.UpdateCommand.Parameters(0).Value)
End Function
'Exposes the Typed DataSet DataAdapter
Public Function GetAdapter() As SqlDataAdapter
Return (Me.Adapter)
End Function
'Exposes the Command Object associated with Database Select Operations
'This is important if Select commands are going to be issued during an
'active Update/Insert/Delete Transaction. The Transaction and its
'associated Connection Object will be set on the SelectCommand object
'to prevent the Update Transaction from Blocking the Select statement.
Public ReadOnly Property SelectCommand() As SqlCommand
Get
Return Me.CommandCollection(0)
End Get
End Property
'Provides Access to the TableAdapters Transaction Object.
Public Property Transaction() As SqlTransaction
Get
If (Not IsNothing((Me.Adapter.UpdateCommand.Transaction))) Then
Return (Me.Adapter.UpdateCommand.Transaction)
ElseIf (Not IsNothing((Me.Adapter.InsertCommand.Transaction))) Then
Return (Me.Adapter.InsertCommand.Transaction)
ElseIf (Not IsNothing((Me.Adapter.DeleteCommand.Transaction))) Then
Return (Me.Adapter.DeleteCommand.Transaction)
ElseIf (Not IsNothing((Me.Adapter.SelectCommand.Transaction))) Then
Return (Me.Adapter.SelectCommand.Transaction)
Else
Return (Nothing)
End If
End Get
Set(ByVal value As SqlTransaction)
If (Not IsNothing(Me.Adapter.UpdateCommand)) Then
Me.Adapter.UpdateCommand.Transaction = value
Me.Adapter.UpdateCommand.Connection = value.Connection
End If
If (Not IsNothing(Me.Adapter.DeleteCommand)) Then
Me.Adapter.DeleteCommand.Transaction = value
Me.Adapter.DeleteCommand.Connection = value.Connection
End If
If (Not IsNothing(Me.Adapter.InsertCommand)) Then
Me.Adapter.InsertCommand.Transaction = value
Me.Adapter.InsertCommand.Connection = value.Connection
End If
End Set
End Property
End Class
End Namespace
The code shown below is the DAL Interface Class required to facilitate the Transaction
sharing across multiple Typed DataSets. Just create an SqlInterface.vb file, paste all the code below into it and add it to your project - you will also need to add the required Imports
to support any TableAdapter
methods you may use in this class to retrieve data from the database.
Placing all the Typed DataSet Fill
methods in the SqlInterface Class
provides a single access point for Data Access and eliminates a lot of unnecessary complexity in your application code that would be required to handle Multi-Typed DataSet Transaction
participation.
Imports System.Data.SqlClient
Public Class SqlInterface
#Region " Singleton Constructor Methods "
'Private Shared reference to this Class required to provide a Singleton instance
Private Shared SqlInterfaceInstance As SqlInterface
'Provides a Singleton reference to this Class Instance
Public Shared Function GetInstance() As SqlInterface
If (IsNothing(SqlInterfaceInstance)) Then
SqlInterfaceInstance = New SqlInterface()
End If
Return SqlInterfaceInstance
End Function
'Private Class Constructor called by the Shared Singleton GetInstance Method
Private Sub New()
'Do not remove this sub. This prevents someone from instantiating another
'SqlInterface Class Instance. Call the 'GetInstance()' method to get an
'instance reference to this Class. This enforces a Singleton Pattern.
End Sub
#End Region
#Region " Private Class Variables "
Private _UsingTransaction As Boolean = False
Private _Transaction As SqlTransaction = Nothing
Private _TransConnection As SqlConnection = Nothing
Private _TableAdapter As SqlDataAdapter = Nothing
Private _TransCommand As SqlCommand = Nothing
#End Region
#Region "Transaction Methods"
'Initiates a Transaction on a Typed DataSet TableAdapter Connection. This
'transaction is automatically assigned to any other Typed DataSet TableAdapter
'initialized through this Interface Class during an active Transaction until
'the transaction is explicitly Committed or Rolled back through the SqlInterface
'Class Instance. (Note: The Private Scope of this method is intentional)
Private Function BeginTransaction(ByVal TableAdapter As SqlDataAdapter) As Boolean
'Be sure we don't already have a transaction initiated
If (Not IsNothing(_Transaction)) Then Return False
'Set Class TableAdapter Object
_TableAdapter = TableAdapter
'Set Class Connection Object
If (Not IsNothing(_TableAdapter.UpdateCommand)) Then
_TransConnection = _TableAdapter.UpdateCommand.Connection
ElseIf (Not IsNothing(_TableAdapter.InsertCommand)) Then
_TransConnection = _TableAdapter.InsertCommand.Connection
ElseIf (Not IsNothing(_TableAdapter.DeleteCommand)) Then
_TransConnection = _TableAdapter.DeleteCommand.Connection
ElseIf (Not IsNothing(_TableAdapter.SelectCommand)) Then
_TransConnection = _TableAdapter.SelectCommand.Connection
Else
Throw New Exception("A Connection could not be established _
because no Command Object has been initialized")
End If
'Open the DB Connection
_TransConnection.Open()
'Set the Class Transaction Object
_Transaction = _TransConnection.BeginTransaction()
'Set the Transaction property for any instantiated Command Objects
If (Not IsNothing(_TableAdapter.UpdateCommand)) _
Then _TableAdapter.UpdateCommand.Transaction = _Transaction
If (Not IsNothing(_TableAdapter.InsertCommand)) _
Then _TableAdapter.InsertCommand.Transaction = _Transaction
If (Not IsNothing(_TableAdapter.DeleteCommand)) _
Then _TableAdapter.DeleteCommand.Transaction = _Transaction
If (Not IsNothing(_TableAdapter.SelectCommand)) _
Then _TableAdapter.SelectCommand.Transaction = _Transaction
Return True
End Function
'This method enlists Adapters used for Database Select
'Operations during an active Transaction into the current
'Transaction and Connection so the Select operation is not blocked
'by the active Update Transaction.
'This is required because the Auto-Generated TableAdpater Class
'is coded in such a way that the DataAdapter's
'SelectCommand is not initialized like the
'Update, Insert and Delete Command Objects. The SelectCommand is instead
'added to the TableAdapater internal CommandCollection
'(it's the ONLY Command object in the collection). So this is
'somewhat of a hack to work around this but at least
'it keeps all the necessary code confined to the TableAdapter
'Extension Class and this DAL Interface Class eliminating the need
'for any complicated code in the general application.
Private Sub EnlistAdapterInTransaction(ByVal Adapter As Object)
Adapter.SelectCommand.Transaction = Me._Transaction
Adapter.SelectCommand.Connection = Me._TransConnection
End Sub
'Commits all DB changes performed during the Transaction and releases
'all resources and SQL DB connections.
Public Function CommitTransaction() As Boolean
If (Not IsNothing(_Transaction)) Then
_Transaction.Commit()
EndTransaction()
Return True
Else
EndTransaction()
Return False
End If
End Function
'Rolls back all DB changes performed during the Transaction and
'releases all resources and SQL DB connections.
Public Function RollBackTransaction() As Boolean
If (Not IsNothing(_Transaction)) Then
_Transaction.Rollback()
EndTransaction()
Return True
Else
Return False
End If
End Function
'Handles cleanup for a DAL initiated transaction
Private Sub EndTransaction()
If (Not IsNothing(_TransConnection)) Then _TransConnection.Close()
If (Not IsNothing(_Transaction)) Then _Transaction.Dispose()
If (Not IsNothing(_TableAdapter)) Then _TableAdapter.Dispose()
End Sub
#End Region
#Region " Public Class Methods "
'Example method that executes a Select Operation on the DataBase
'with a check for an active
'transaction. If a transaction is active on the Connection,
'the SelectCommand object from
'the TableAdapter is enlisted into that Transaction
'so it is not blocked by the active Transaction.
'Note: The Typed DataSet name shown in the example is 'TdSomeData'
Public Function GetSomeDataByKey(ByVal Key As Integer) As TdSomeDataDataTable
Dim TdAdapter As New TdSomeDataAdapter
'See if an active transaction exists on the DAL and enlist
'the TableAdapter in the Transaction if there is.
If (Not IsNothing(Me._Transaction)) Then EnlistAdapterInTransaction(TdAdapter)
Return (TdAdapter.GetSomeData(Key))
End Function
#End Region
#Region " Public Class Properties "
'This Property provides access to an active Transaction object
'regardless of what Typed DataSet initiated the transaction.
Public ReadOnly Property Transaction(ByVal TableAdapter As SqlDataAdapter) _
As SqlTransaction
Get
If ((Me.UsingTransAction) AndAlso (IsNothing(_Transaction))) Then
Me.BeginTransaction(TableAdapter)
End If
Return (_Transaction)
End Get
End Property
'Class flag indicating a Transaction is to be used for
'subsequent DB changes until committed or rolled back.
'This flag is required to initiate a transaction on
'subsequent TableAdapter reads/writes on the underlying Database.
'The SqlInterface Class Instance (DAL Interface) will
'automatically initiate and maintain the Command, Connection and
'Transaction objects across multiple Typed DataSet TableAdapter
'interactions with the Database until the Transaction
'is explicitly Committed or Rolled back. Setting this property to True
'automatically begins a transaction when required.
Public Property UsingTransAction() As Boolean
Get
Return (_UsingTransaction)
End Get
Set(ByVal value As Boolean)
_UsingTransaction = value
End Set
End Property
#End Region
End Class
Here's an example of how to use the SQLInterface Class
in your general application code:
'Declare a local Class variable of the SQLInterface Class
'(you don't have to do this - you can use SqlInterface.GetInstance
'if you like, I just like shorter method call strings.
'So in the example method below, you could use:
'SqlInterface.GetInstance.UsingTransAction = True
'if you prefer not to use a Class variable like I did in my example.
Private SQL As SqlInterface = SqlInterface.GetInstance
Public Sub Save()
Try
'Set the DAL Interface Transaction Flag.
'This instructs the SqlInterface Class to begin a transaction
'or enlist in an existing active transaction when the
'SqlInterface Transaction Property is accessed.
'As long as this flag was True the first time the
'SqlInterface Transaction property was assigned to a
'Typed DataSet's TableAdapter Transaction property,
'any other Typed DataSets that assign the SqlInterface
'transaction property to their transaction property will
'automatically be enlisted in the existing Transaction
'even if the 'UsingTransAction' flag has been reset to False.
'To terminate an existing SqlInterface Transaction,
'you MUST call either the SqlInterface CommitTransaction or
'RollBackTransaction method.
'Note that either of these methods will reset the 'UsingTransAction' flag.
SQL.UsingTransAction = True
'Do some code processing here that will cause the Typed DataSet
'to Modify a Table the DB. To use the
'MyTypedDataSetAdapter in the method below, we would need to have an
'Imports Statement at the top of
'this Class file something like this:
'Imports <Solution Name> .MyTypedDataSetTableAdapter
If (Me.HasChanges) Then
Dim TdAdapter As New MyTypedDataSetAdapter
'Assign the SqlInterface Transaction to the TableAdapter
'Transaction Property if the 'UsingTransaction'
'Flag has been previously set, this line of code will either
'begin a transaction or enlist this Typed
'DataSet's TableAdapter in the current Transaction that was
'initiated by another Typed DataSet
'participating in this Transaction.
If (SQL.UsingTransAction) Then TdAdapter.Transaction =
SQL.Transaction(TdAdapter.GetAdapter())
'Call the Update Method to save Data to the DB
TdAdapter.Update(Param1, Param2, Param3)
End If
'Commit the Transaction
SQL.CommitTransaction()
Catch ex As Exception
'Something went wrong, Rollback the Transaction
SQL.RollBackTransaction()
'Throw the Exception so it can be caught and displayed if required
Throw ex
End Try
End Sub
That's it! If you've been avoiding the use of Typed DataSets because you didn't think you could use a single transaction for multiple Typed DataSet updates without using the costly Transaction
scope, I hope this article changes your mind. I have found Typed DataSets to be a powerful feature of the .NET Framework handling most of the underlying complexities of database interaction. Typed DataSets make updating your code easy as the underlying database schema changes with the evolution of your application. I hope you find these classes to be useful!
Points of Interest
Something I learned while developing this idea that surprised me was that the SelectCommand
object is not used by the Typed DataSet Adapter
Class. I found it even more strange that the auto-generated code only placed the SelectCommand
object in the CommandObject
collection and did not place any of the other Command
objects in the collection. The reference to each of them was assigned to their respective command objects (Update
, Insert
, Delete
).
History
- 4th May, 2008: Initial post