First off, I would like to draw your attention to the key abbreviation in the title of this article. VSTO stands for Visual Studio Tools for Office, which is a set of classes and wizards delivered with Visual Studio 2008. VSTO is what the major part of Microsoft Office developments is based on these days. So, if you are determined to go on reading, you are welcome to the Visual Studio Ecosystem. Forget about the Visual Studio Shell which is installed by Delphi Prism if it does not find Visual Studio already installed. Yes, you need to have the full-fledged Visual Studio 2008, at least the Professional edition.

Another word combination which I used in the title of the article is "application-level extensions". Now it is the generally accepted term for what was earlier called COM Add-ins for Microsoft Office. One more variant is application-level add-ins.

Why may you want to use Delphi Prism for developing VSTO-based projects?

At first sight there can be only one answer here. You surely still prefer typing begin-end rather than braces or sub-end sub. And, like me, you haven’t given up programming in Delphi yet :) Though, we need to discuss right away the question of economics which is very crucial these days, or more precisely, that of economy. And there isn’t a trace of economy here. As I mentioned above, you need to have Visual Studio 2008 Professional (or Team System) and Delphi Prism.

However, for me this disadvantage is more than compensated for by just three features that Delphi Prism has on board, which I am going to use to the utmost in my Office extensions: dbExpress IV (aka Heterogeneous Database Access), DataSnap (Multi-tier Client Development) and parallel programming language features (support of the Microsoft PFX Framework).

Now VSTO directly supports only two programming languages – VB.NET and C#. It is these languages that are now in focus of Microsoft’s attention in the framework of Microsoft Office System development. But what shall we, begin-end aficionados, do? The other day I uploaded version 1 of the new extension for Visual Studio 2008 that supports VSTO-based solutions in Delphi Prism. You can download it from Code Central and use for free.

So, here is what you need for developing VSTO-based application-level extensions for Microsoft Office in Delphi Prism:

• Visual Studio 2008 (Pro or TS) with VSTO installed
• Delphi Prism
• The VSTO Support for Delphi Prism Wizard
• Finally, Microsoft Office 2003 or 2007 installed on you PC.

Using Delphi Prism you can develop extensions for all Office applications and Office versions supported by VSTO, namely:

You have the following features of MS Office and VSTO available to you:

If you still remember what Office Sample Automation Server Wrapper Components are, and have little or no experience in VSTO development, you will find the resources below pretty helpful. Quite naturally, all of them will bring you to MSDN.

• Office Developer Center – CDN for all MS Office developers; news, downloads, documentation, community, featured resources; in general, all about Office development.
• VSTO Developer Center – this resource targets VSTO-based Office development; here you will find VSTO-related news, downloads, links to documentation, community and examples.
• Office Development in MSDN Library – part of the MSDN Library which covers programming in, over, on and upon Microsoft Office :)
• VSTO Development in MSDN Library – part of the MSDN Library that is completely focused on programming in VSTO.
• Getting Started Programming Application-Level Add-Ins – a must-read article for those who want to start developing COM add-ins in Delphi Prism using VSTO.

Subject to the above mentioned requirements, Delphi Prism provides full support for developing VSTO-based application-level add-ins for Microsoft Office, including code generation and msi-based deployment, and, of course, such in-demand features as the Ribbon designer, Outlook 2007 regions and Office Task panes. And there are no principle limitations in using the VSTO programming model when you employ Delphi Prism in your Office development.