How To Use RDS to Access MTS Components Over the Internet

This article explains how to use Remote Data Services (RDS) from a Visual Basic client to access your MTS components through HTTP. This service is useful when you want to extend the reach of your MTS applications beyond your local Intranet or a Web browser that uses ASP.

RDS is a programming model that uses an intermediate service, such as IIS, to obtain and manipulate data and objects. This intermediate service actually creates the object and allows the client code to access that object as if the client created the object itself. The complete object model and documentation for RDS can be found here:

http://msdn.microsoft.com/library/en-us/dnoledb/html/usingthecustomizationhandlerfeatureinrds21.asp (http://msdn.microsoft.com/library/en-us/dnoledb/html/usingthecustomizationhandlerfeatureinrds21.asp)

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Following is an explanation illustrating how to create an MTS component, installing the component into MTS, and creating a Visual Basic client application that access the MTS component through HTTP.

Create a Simple MTS Component

1. Create a new ActiveX DLL project.
2. Rename the project to "Calculate" and Class1 to CCalculate.
3. Insert the following code into the CCalculate class module:

   Public Function GetSum(ByVal Num1 As Integer, ByVal Num2 As Integer) As Integer
     GetSum = Num1 + Num2
   End Function
   						

4. Compile the project and make the DLL.

Setting up MTS

1. Install the compiled DLL into MTS.
2. Create a new Package in the MTS Explorer and set it's Identity to run as a user other than Interactive.
3. Add the Calculate.dll file to the components folder.
4. In order to get RDS to invoke the MTS component, a registry key must be added that tells IIS that it is ok to create your object.
5. Add the following key:
   
   

   \HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\W3SVC\Parameters\ADCLaunch\Calculate.CCalculate
   						

Create the Visual Basic Client

1. Begin by creating a new Standard EXE project.
2. On Form1 add two Text Boxes (Text1 and Text2) and a Command Button (Command1).
3. Add the following code to the Form:
   
   

   Private Sub Command1_Click()
     Dim rds As Object
     Dim objCCalculate As Object
   
     Set rds = CreateObject("RDS.DataSpace")
     Set objCCalculate = rds.CreateObject("Calculate.CCalculate", "http://YourHTTPServerName")
   
     MsgBox objCCalculate.GetSum(CInt(Text1), CInt(Text2))
   
     Set rds = Nothing
     Set objCCalculate = Nothing
   End Sub
   						

When the client executes and you click Command, RDS asks the Web Server to create the MTS object. The Web Server then returns a reference to the MTS object and the client can use the reference as it would any other MTS object.

For additional information, click the article number below to view the article in the Microsoft Knowledge Base: