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Building an Extendable Application

In the sections that follow, I will take you through a complete example that illustrates the process of

building an extendable Windows Forms application that can be augmented by the functionality of

external assemblies. What I will not do at this point is comment on the process of programming

Windows Forms applications (see Chapter 27 for an overview of the Windows Forms API). So, if you

are not familiar with the process of building Windows Forms applications, feel free to simply open

up the supplied sample code and follow along. To serve as a road map, our extendable application

entails the following assemblies:

C H A P T E R   1 6  

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• CommonSnappableTypes.dll: This assembly contains type definitions that will be used by each

snap-in object and will be directly referenced by the Windows Forms application.

• CSharpSnapIn.dll: A snap-in written in C#, which leverages the types of

CommonSnappableTypes.dll.

• VbNetSnapIn.dll: A snap-in written in Visual Basic, which leverages the types of

CommonSnappableTypes.dll.

• MyExtendableApp.exe: This Windows Forms application will be the entity that may be

extended by the functionality of each snap-in.

Again, this application will make use of dynamic loading, reflection, and late binding to

dynamically gain the functionality of assemblies it has no prior knowledge of.