Opening Outlook 365 window from WPF .Net Core app

Question

This question has been asked many items, but I wasn't able to find appropriate actual solution.

I am developing WPF app using .Net Core 3.1 and need to open Outlook (365, 16.0.12827.20328) window with new email and attachments. The easiest way is using Interop.

My code:

        Microsoft.Office.Interop.Outlook.Application oApp = new Microsoft.Office.Interop.Outlook.Application();
        MailItem oMsg = (MailItem)oApp.CreateItem(OlItemType.olMailItem);

        oMsg.Subject = "subject";
        oMsg.BodyFormat = OlBodyFormat.olFormatHTML;
        oMsg.HTMLBody = "body";
        oMsg.Attachments.Add("filepath", OlAttachmentType.olByValue, Type.Missing, Type.Missing);

For this I need Interop package. I tried installing nuget Microsoft.Office.Interop.Outlook and adding reference COM -> Interop.Microsoft.Office.Interop.Outlook.

In both scenarios I get error: System.IO.FileNotFoundException: 'Could not load file or assembly 'office, Version=15.0.0.0, Culture=neutral, PublicKeyToken=71e9bce111e9429c'. The system cannot find the file specified.'

What do I have to do to solve the issue? And why I need version 15.0.0.0? Internet says that version 15 is for Outlook 2013.

An interop dll will be generated when you reference Outlook from the COM tab instead of using NuGet. Does that work? — Dmitry Streblechenko
@DmitryStreblechenko as I've mentioned, I tried referencing COM -> Interop.Microsoft.Office.Interop.Outlook, but it gives the same error — Roman
I think you are missing my point: you can add a reference to an existing interop dll, or you can add a reference to a COM library and VS will generate an interop dll for you. I meant the latter option. — Dmitry Streblechenko

Eugene Astafiev Eugene Astafiev · Accepted Answer · 2020-07-23T17:47:48

Typically for automating Outlook you must add the following COM references:

Microsoft Office type library - for common MS Office types.
Microsoft Office Outlook type library - for Outlook specific types.

You may try to create a new .net framework application and add these COM references. Or just try creating a new VSTO add-in and observe the added COM references.

Opening Outlook 365 window from WPF .Net Core app

1 Answers