Q248098: PRB: ErrMsg: Method Call on MTS Object from VB App Fails
Article: Q248098
Product(s): Microsoft Visual Basic for Windows
Version(s): 2.0,4.0,6.0
Operating System(s):
Keyword(s): kbMTS kbMTS200 kbVBp600 kbOSWinNT400sp3 kbGrpDSVBDBkbfaq
Last Modified: 06-JUN-2001
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The information in this article applies to:
- the operating system: Microsoft Windows NT 4.0
- Microsoft Transaction Server 2.0
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0
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SYMPTOMS
========
When you attempt to invoke a method on a Transactional Microsoft Transaction
Server (MTS) object from a Visual Basic client application, the following error
message is displayed:
Runtime error -2147164145(800e400f): Method [methodname] of object
[objectname] failed.
CAUSE
=====
MTS components use the services of the Microsoft Distributed Transaction
Coordinator (MS DTC) to incorporate transactional functionality. Invoking
methods of an MTS component that call transactional methods of the Objectcontext
object, such as SetComplete() and SetAbort(), may cause the error message. This
error message occurs if methods of the MTS component are called, and the MS DTC
service has not been started on the Windows NT-based computer that is hosting
the component and running Transaction Server.
RESOLUTION
==========
Start the MS DTC service on the Windows NT-based computer that is running
Transaction Server in one of two ways:
Method 1:
1. On the Start menu, point to Settings, and then click Control Panel.
2. Double-click Services to open the Services dialog box.
3. Select MSDTC in the list of Services.
4. Click Start to initiate the service.
Method 2:
If the Windows NT-based computer also runs Microsoft SQL Server, use the SQL
Server Service manager to start MS DTC.
STATUS
======
This behavior is by design.
MORE INFORMATION
================
MTS uses the services of MS DTC to support and incorporate the transactional
functionalities of components that are registered in it. Therefore, the MS DTC
service must be active for transactional methods of MTS components to be
executed successfully. The error message in the "Symptoms" section is not a bug
in any of the Microsoft products listed in the Applies to section of this
article.
Steps to Reproduce Behavior
---------------------------
NOTE: The following example is included for illustration purposes only. It uses
the SQL 7.0 Pubs database, and assumes that the Windows NT Option Pack is
installed on the computer that is running Visual Basic. The error message
documented in this article can be reproduced by invoking the method of any
transactional MTS component with the MS DTC service stopped on the MTS Server
computer.
Creating the Sample Visual Basic COM Component:
1. Create a new ActiveX DLL project in Visual Basic.
2. Rename the Class module from Class1 to clsAuthor, and set its
MTSTransactionMode property to 2-RequiresTransactions.
3. Save the project as MTSPubs.vbp, and save the class module as clsAuthor.cls.
4. On the Project menu, click References, and then set a reference to Microsoft
ActiveX Data Objects 2.X Library.
5. Make the following declarations in the General Declarations section of the
'clsAuthor' Class module:
Dim cn As ADODB.Connection
Dim rs As ADODB.Recordset
6. Initialize and open the ADO Connection object in the Class_Initialize() event
as shown in the following code. Replace the connection string with one that
points to your SQL Server.
Private Sub Class_Initialize()
Set cn = New ADODB.Connection
cn.ConnectionString = "Provider=SQLOLEDB;Data Source=RAVINDK1;Initial Catalog=pubs;Trusted_Connection=yes"
cn.Open
End Sub
7. Add a method called GetAuthors that constructs and returns a disconnected
recordset from the Pubs database that contains records from the Authors table
as follows:
Public Function GetAuthors() As Object
Set rs = New ADODB.Recordset
Set rs.ActiveConnection = cn
rs.LockType = adLockBatchOptimistic
rs.CursorLocation = adUseClient
rs.CursorType = adOpenStatic
rs.Open "Select au_fname, au_lname from Authors"
Set rs.ActiveConnection = Nothing
Set GetAuthors = rs
GetObjectContext.SetComplete
End Function
8. Save the project, on the File menu, choose Make MTSPubs.dll to compile the
DLL, and then close Visual Basic.
Installing the Component in MTS:
1. Start MTS Explorer, and create a package.
2. Add the component you just created in Visual Basic by right-clicking on the
Components folder of the package. Under New, click Component, click Install
New Components, and then select the DLL.
3. After the component has been registered in MTS Explorer, check its properties
to ensure that its Transaction attribute has been set to Requires
Transactions.
Setting Up the Visual Basic Client to Reproduce the Problem:
1. Create a standard EXE project in Visual Basic to implement the client
application that will invoke the MTS component and call its GetAuthors method
to retrieve the disconnected recordset. On the Project menu, click
References, and then set a reference to the Microsoft ActiveX Data Object 2.X
Library.
2. Place a Listbox control on the default Form1, place a Command button beneath
the list box, and set its Caption property to Get Authors.
3. Make the following declarations in the General declarations section of the
form module:
Dim mauthor As Object
Dim aurset As ADODB.Recordset
4. Place the following code in the Form_Load() event to create an instance of
the MTSPubs.clsAuthor MTS object:
Private Sub Form_Load()
Set mauthor = CreateObject("MTSPubs.clsAuthor")
End Sub
5. Place the following code in the Click event of the Command button. This code
calls the GetAuthors method of the MTS object and returns the disconnected
recordset that contains the records from the Authors table in the SQL 7.0
Pubs database.
Private Sub Command1_Click()
Set aurset = mauthor.GetAuthors
List1.Clear
Do While Not aurset.EOF
List1.AddItem aurset.Fields("au_fname")
aurset.MoveNext
Loop
aurset.Close
End Sub
6. Save the project as MTSClnt, and save the form as frmTest. Make sure that the
MS DTC Service is not running on the Windows NT-based computer. You can shut
it down by using the SQL Server Service Manager if the SQL server to which
you are connecting is installed on the MTS computer. You can also stop the
Msdtc.exe process from the Windows NT task manager.
7. Run your client project, MTSClnt, and note that an instance of your MTS
object is created in the Form_Load() event. Then the form, frmTest, is
displayed.
8. Click on the Command button labeled Get Authors, and note that you receive
the following error message:
Runtime error -2147164145(8004e00f): Method 'GetAuthors' of object
'_clsAuthor' failed.
9. Click End to stop the execution of the project, and then return to the design
environment.
10. Start the MS DTC service on the MTS computer, rerun the project, and note
that when you click on the Get Authors Command button, the list of authors
(first name, and last name) is displayed in the list box on the form.
Additional query words: VB 6.0 VB6
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Keywords : kbMTS kbMTS200 kbVBp600 kbOSWinNT400sp3 kbGrpDSVBDB kbfaq
Technology : kbVBSearch kbMTSsearch kbAudDeveloper kbOSWinSearch kbOSWinNT400 kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVB600 kbMTS200 kbOSWinNTSearch
Version : :2.0,4.0,6.0
Issue type : kbprb
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