Represents a single add-in, either installed or not installed.
Assembly: Microsoft.Office.Interop.Excel (in Microsoft.Office.Interop.Excel.dll)
The AddIn object is a member of the AddIns collection. The AddIns collection contains a list of all the add-ins available to Microsoft Excel, regardless of whether they’re installed. This list corresponds to the list of add-ins displayed in the Add-Ins dialog box (Tools menu).
Use AddIns(index), where index is the add-in title or index number, to return a single AddIn object.
Don’t confuse the add-in title, which appears in the Add-Ins dialog box, with the add-in name, which is the file name of the add-in. You must spell the add-in title exactly as it’s spelled in the Add-Ins dialog box, but the capitalization doesn’t have to match.
The index number represents the position of the add-in in the Add-ins available box in the Add-Ins dialog box.
The Add method adds an add-in to the list of available add-ins but doesn’t install the add-in. Set the Installed property of the add-in to True to install the add-in. To install an add-in that doesn’t appear in the list of available add-ins, you must first use the Add method and then set the Installed property. This can be done in a single step
Use Workbooks(index) where index is the add-in filename (not title) to return a reference to the workbook corresponding to a loaded add-in. You must use the file name because loaded add-ins don’t normally appear in the Workbooks collection.
If the Installed property returns True, but calls to functions in the add-in still fail, the add-in may not actually be loaded. This is because the Addin object represents the existence and installed state of the add-in but doesn't represent the actual contents of the add-in workbook. To guarantee that an installed add-in is loaded, you should open the add-in workbook.