How to load an Excel Addin using Interop

Question

I have an AddIn which I want to invoke through Excel interop from a C# winforms application.

I can\'t get the addin etc. to load unless I uninstall and resinstall it

Answer 1

After a while I found the answer hidden in strange places in the MS help: and this blog post.

That isn't all the info you need though. Things to note: you must have at least one workbook open or otherwise Excel barfs. Here's some rudementry code to get started:

var excel = new Application();
var workbook = excel.workbooks.Add(Type.Missing);
excel.RegisterXLL(pathToXll);
excel.ShowExcel();

If you want you can close the temporary workbook (if you've run some macros etc.) and remember to tidy everything up with plenty of calls to Marshal.ReleaseComObject!