[FAQ's: OD] How do I automate an Office App using C#?

[RobDog888]

You can automate just about any of the Office suite application. Office OneNote 2003 is one app that has limited programmatical support. Only two functions are exposed.

Excel, Word and Outlook are the Office Apps that get all the attention because of their vast ability to be customized and automated, not to mention that they themselves are widely used and popular.


Office Automation involves using COM (Microsoft® OLE Component Object Model).

There are several aspects to be concerned with when performing automation of Office applications:

• Early vs Late Binding
• The Office Application Version(s)
• Security
• Distribution

If your planning on only supporting one version of the Office application your automating then you dont have to worry about other versions so Early Binding would be good. Also, you get the Intelisense popups with Early Binding and not with Late. So Late Binding is best if your going to be supporting multiple versions of Office as the referene needs to be dynamic and attach when created in your program. Late Binding also requires you to either use the actual value of all constants or define them yourself with the appropriate values. With C# Late Binding requires you to use Reflection so you can specify the type of object and what function, methods and properties you are needing to access in your code.

If your not going to be distributing the Program or Add-In then your only needing to support a single Office version. This makes like allot easier but if you ever upgrade your Office version then you will need to recompile your program or Add-In after you have updated the references to your new version.

Security is another aspect to consider when choosing the type of program architecture your going to use. If its just a small .NET program automating and Office app or an all out Add-In. Each type has its pros and cons. They do preset security issues between the Office Application and the .NET program as the Office Applications have some built in security and you are also performing cross process marshalling so depending on the operations being performed you may need to code taking that into consideration. For the most power and security you would want to write a COM Add-In using .NET vs. just automating it with the basic .NET program. You can have even more power in your automation if you have Visual Studio Tools for Office (VSTO) available to you. With a COM Add-In you get an easier way to distribute the program, more security for your code, and security between Applications and for the ultimate in Office Automation you will want to use VSTO.


For more information on Office Add-Ins check out my other FAQ thread - "How do I use .NET to make an Add-In for an Office application?"

Also, for more information on VSTO, see this thread - "How do I make my first VSTO 2003 application?"
and this thread - "How do I make my first VSTO 2005 application?"

C# Code Examples below in post #2 and #3.