Business Logic in MTS Components

[This product will work only on Windows NT 4.0 versions and earlier. For Windows 2000 and later, see COM+ (Component Services).]

This topic describes how to enact business logic in MTS components.

Granularity is determined by the number of tasks performed by a component. The granularity of a component affects the performance, debugging, and reusability of your MTS components. A fine-grained component performs a single task, such as calculating tax on a sales order. Fine-grained components consume and release resources quickly after completing a task. A component that enacts a single business rule can facilitate testing packages, because isolating individual tasks in components makes testing your applications easier. In addition, fine-grained components are easily reused in other packages. In the following example, a component performs a single task: adding a customer record to the database.

Function Update(ByVal strEmail As String, _
ByVal bNewCust As Boolean, ByVal strContact As String,_
ByVal strPhoneNumber As String, _
ByVal strNightPhoneNumber As String)

    Dim ctxObject As ObjectContext
    Set ctxObject = GetObjectContext

    On Error GoTo ErrorHandler

' Code accesses the customer row from the database.
' Customer information is updated with information
' that was passed in.
'
    ctxObject.SetComplete

    Exit Function

This simple component uses system resources efficiently (passing parameters by value), is easy to debug (single function), and also reusable in any other application that maintains customer data.

A coarse-grained component performs multiple tasks. Coarse-grained components are generally harder to debug and reuse in applications. For example, a PlaceOrder component might add a new order, update inventory, and update customer information. PlaceOrder is a more coarsely grained component because it performs more "work" by adding, updating, and deleting customer, inventory and order information.

For more information about components' shared resources, see Holding State in Objects.