How to get Outlook's Web AddIn ItemId in Outlook's VSTO AddIn?

Question

As you know, you can create both Web and VSTO AddIns for Outlook on Visual Studio, but I'm having trouble retrieving the item id on VSTO AddIns, as there is no such property in the MailItem object.

In Web AddIns you can retrieve said property like this, this behaviour is actually included in the AddIn's template:

(function () {
Office.onReady(function () {
    $(document).ready(function () {
        loadItemProps(Office.context.mailbox.item);
    });
});

function loadItemProps(item) {
    $('#item-id').text(item.itemId);
}
})();

But in VSTO AddIns, using the MailItem object, you can only retrieve other values such as ConversationID or EntryID, and these don't work for me.

The reason why I need the ItemId is because the value gets sent to PowerApps to load an app which loads content related to the email, such as attachment files, and the GetEmail function in PowerApps does not understand other values such as EntryID, it requires a messageId.

I have read this question but it only returns what appears to be an email address, and not the same value you can get with the Web AddIn.

Answer 1

Our team does not have a lot of expertise in VSTO/COM add-ins, so there may be another solution than this...but it is possible to convert EntryID's to an EWSId via the EWS Method ConvertId's

https://learn.microsoft.com/en-us/exchange/client-developer/web-service-reference/convertid-operation