About Pipeline Components

Article
11/12/2009

A pipeline component is a Component Object Model (COM) server object that implements the IPipelineComponent interface. The following is the definition of this interface as it appears in the Pipecomp.idl file:

    interface IPipelineComponent : IUnknown
    {
        import "oaidl.idl";

        HRESULT Execute(
                    [in]            IDispatch*  pdispOrder,
                    [in]            IDispatch*  pdispContext,
                    [in]            LONG        lFlags,
                    [out,retval]    LONG*       plErrorLevel
                );

        //
        // By default, a pipeline is in "execution mode", this call is
        // used to prepare the pipeline for "design mode" (fEnable ==
        //  TRUE) or to go to design mode (fEnable = FALSE).
        //

        HRESULT EnableDesign( [in]    BOOL fEnable );

    };

When the pipeline creates an instance of a component, it requests an interface pointer to the IPipelineComponent implementation of the component, then uses this pointer to invoke the IPipelineComponent::Execute method.

IPipelineComponent is the only interface that a component must implement to function within the pipeline. However, to enhance the usability of a component, or to take advantage of the transaction capabilities of COM+, you may also design your component to implement one or more of the following interfaces:

IDispatch. Implementing this interface is optional. However, it makes it possible for clients to access the capabilities of your component from macro languages, such as Visual Basic Scripting Edition (VBScript) or Visual Basic.
IPipelineComponentAdmin. This interface is a component configuration interface. If your component requires configuration at design time, then you should implement this interface. The IPipelineComponentAdmin interface defines the GetConfigData and SetConfigData methods, to which the caller passes a Dictionary object. The GetConfigData and SetConfigData methods write or read this Dictionary object to retrieve or set configuration data on the component.
IPipelineComponentDescription. When you implement this interface, you identify to the Pipeline Editor the keys and values in the OrderForm object that your component reads and writes, as well as the pipeline context values that your component uses. The Pipeline Editor displays these keys when the user selects the Values Read and Written tab for the component.
IPersistStreamInit. This interface allows components written in C++ to save data to the configuration file. Visual Basic components cannot implement this interface. For Visual Basic components, the IPipelineComponentAdmin interface is used to get and save data to and from the configuration file.
ISpecifyPropertyPages. This interface allows your component to specify property pages for use in the Pipeline Editor.

About Pipeline Components

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