VSTO with .NET Core 3.0

Question

I was wondering if the VSTO works on the new .NET Core 3 which supports COM Objects. A Project can be created with .Net Framework and then migrate it to .NET Core by modifying the .csproj file, but will be the VSTO compatible ? If not, is there an alternative to the VSTO in .NET Core 3 ?

Answer 1

It seems like there is currently no alternative. There is a request to add this support in the future to .Net 5 https://developercommunity.visualstudio.com/idea/757925/please-port-visual-studio-tools-for-office-vsto-to.html

The recommendation currently seems to be using the Office JS platform to create add-ins. These will be compatible across platforms also (https://blogs.msdn.microsoft.com/deva/2018/04/02/office-developer-difference-between-office-web-addin-vs-comvsto-addin)

Answer 2

VSTO does not currently support .Net core.
But nothing prevents you from creating a pure COM based addin by implementing a COM object that exposes the IDTEXtensibility2 interface.
The question is why do you need to develop an addin using .Net Core alone? Your addin will run on a machine with the Office suite installed, which mean .Net run-time will also be installed.