HOWTO: Create a 3-Tier App Using VB, MTS, and SQL Server

• ActiveX Data Objects (ADO), versions 2.0, 2.1, 2.1 SP2

SUMMARY

This article describes how to create a Visual Basic database application, which uses components that are installed under Microsoft Transaction Server (MTS). The steps in the MORE INFORMATION section outline what is necessary to set up the database application using Visual Basic (VB) and MTS.

This article assumes that you are running MTS 2.0 and SQL Server 6.5 on the same computer on which you develop the application.

MORE INFORMATION

To set up an application that uses remote components running under the control of MTS there are four basic steps:

1. Create the server component. This is an ActiveX DLL written in Visual Basic.



2. Create the client application. This is a standard EXE written in Visual Basic.



3. Install the server components into a MTS package.



4. Setup the client computers (if necessary).

Step 1: Creating the Remote Component

1. Create a new Visual Basic ActiveX DLL project.



2. From the Project menu, choose References and add a reference to the Microsoft ActiveX Data Objects 1.5 Library and to the Microsoft Transaction Server Type Library.



3. From the Project menu, choose Project Properties. Click the General tab and change the Project Name to MTSTest. Make sure that the Threading Model is Apartment Threaded.



4. Add the following code to the GENERAL DECLARATIONS section of the default class module:




   Option Explicit

   Public Function Database_Test_Method( _
   ByVal szConnect As String) As String

      On Error GoTo errhandler

      Dim ctxObject As ObjectContext
      Set ctxObject = GetObjectContext()

      Dim cn As ADODB.Connection
      Dim rs As ADODB.Recordset

      Set cn = New ADODB.Connection
      With cn
         .ConnectionTimeout = 10
         .ConnectionString = szConnect
         .Open
      End With

      Set rs = New ADODB.Recordset
      rs.Open "SELECT * FROM Authors", cn, adOpenForwardOnly, _
              adLockReadOnly

      Database_Test_Method = "First value from database:  " _
                           & rs(0).Value

      rs.Close
      cn.Close

      Set rs = Nothing
      Set cn = Nothing

      ctxObject.SetComplete
      Exit Function

      errhandler:

         ctxObject.SetAbort
         Err.Raise vbObjectError, "MTSTest.Class1.Database_Test_Method", _
                                   Err.Description
         Exit Function

   End Function

   Public Function General_Test_Method() As String

      On Error GoTo errhandler

     Dim ctxObject As ObjectContext
      Set ctxObject = GetObjectContext()

      General_Test_Method = "String from General_Test_Method"

      ctxObject.SetComplete
      Exit Function

      errhandler:
         ctxObject.SetAbort
         Err.Raise vbObjectError, "MTSTest.Class1.General_Test_Method", _
                                   Err.Description
         Exit Function

   End Function 

5. Compile the project into a DLL.

Step 2: Creating the Client Application

1. Create a new Visual Basic standard EXE project.



2. Add two Command buttons to the standard form.



3. Add the following code to the GENERAL DECLARATIONS section of the form:




   Private Sub Command1_Click()
      Dim obj As Object
      Set obj = CreateObject("MTSTest.Class1")

      MsgBox obj.General_Test_Method
      Set obj = Nothing
   End Sub

   Private Sub Command2_Click()
      Dim szConnect As String
      szConnect = "Driver={SQL Server};" & _
            "Server=YourServerName;Uid=sa;Pwd=;Database=pubs"

      '(NOTE: You may need to change the connection
      ' information to connect to your database.)

      Dim obj As Object
      Set obj = CreateObject("MTSTest.Class1")

      MsgBox obj.Database_Test_Method(szConnect)
      Set obj = Nothing

   End Sub

  Private Sub Form_Load()

      Command1.Caption = "Call General_Test_Method"
      Command2.Caption = "Call Database_Test_Method"

   End Sub 

Step 3: Installing the Component Into MTS

1. Start the Microsoft Management Console (MMC), Transaction Server Explorer.



2. Using the Treeview in the left-hand pane, expand each folder by clicking the plus sign beside the folder. First, select and expand Microsoft Transaction Server, then expand Computers, then My Computer and finally expand Packages Installed.



3. Right-click Packages Installed, select New and then choose Package.



4. When the Package Wizard screen displays, select Create and Empty Package. Name the package MTSTest and have it run as the interactive user.



5. Select the Components folder under the newly created package, right-click, choose New and then select Component.



6. Select Import component(s) that are already registered and choose MTSTest.Class1 from the list that displays.

(Optional) Step 4: Setting up Remote Clients

Steps to Create the MTS Setup Program

1. Start Microsoft Management Console.



2. Using the Treeview in the left-hand pane, expand each folder by clicking the plus sign beside the folder. First, expand Microsoft Transaction Server, then Computers, My Computer and then expand the MTSTest Package folder.



3. Right-click the MTSTest package, select Export, and then select the directory to which you want to export the package.



4. Navigate to the directory to which you exported the package and open the clients directory. In this directory, you will find an executable built by exporting. Move this EXE to the CLIENT computer and run the EXE. (Do NOT run this program on the server). This program correctly registers the remote components on the client computer.



5. Run the client setup EXE for the client application, created in step 2, on the client computer.

REFERENCES

MTS 2.0 Online Help

For additional information about distributing Visual Basic Clients using the Visual Basic setup wizard, please see the following articles in the Microsoft Knowledge Base:

Q161837 HOWTO: Create a DCOM Client/Server Application

Q177394 HOWTO: Troubleshoot Run-Time Error '429' in DCOM Applications

Q172869 HOWTO: Debug a Component Written with Visual Basic 5.0

Additional query words:

Keywords : kbADO200 kbDatabase kbDCOM kbMTS kbVBp600 kbGrpVBDB kbGrpMDAC kbDSupport kbADO210sp2 kbMDAC210SP2
Version : WINDOWS:2.0,2.1,2.1 SP2
Platform : WINDOWS
Issue type : kbhowto