为什么 Outlook 在使用 Office 互操作时会崩溃？

Question

I am attempting to utilize Office interop with C#, but I'm having some difficulties. Executing a test like the one I included below seems to work insofar as it launches Outlook and seems to connect with it. The issue is that if I then try to open the Outlook window (it starts hidden in the tray) I get an error message from Outlook saying The application was unable to start correctly (0xc0000142). I do not get this error if Outlook was already running before I started my application. Am I doing something incorrectly or is something broken?

using System;
using Outlook = Microsoft.Office.Interop.Outlook;

namespace OutlookInteropTest1
{
    class Program
    {
        static void Main(string[] args)
        {
            var app = new Outlook.Application();
            Console.ReadKey();
        }
    }
}

Visual Studio Community 2017 Version 15.2

Office 360 - Outlook Version 1804 Build 9226.2156

Windows 10 Build 17115.1

EDIT: Tested this on Windows 7 and could not reproduce crash. I know that I had this working in Windows 10 at some point. I reinstalled my OS and it still crashes. I'm chocking this up to the typical Microsoft user experience unless anyone has any ideas on how to fix it.

Answer 1

Outlook is a singleton, so creating a new object will return the existing object if Outlook is already running.

In your case you also need to provide namespace to it

olApp = new Outlook.Application();
Outlook.Namespace ns = olApp.GetNamespace("MAPI");
ns.Logon();

Answer 2

I know this is old, but I was having the same issue and perhaps it will help someone in the future: As IAmRajshah mentioned, only one istance of outlook can run, so, if Outlook is open your code olApp = new Outlook.Application(); will crash, you need to "connect" to the active instance of outlook with somenthing like this Oulook.Application olApp = Marshal.GetActiveObject("Outlook.Application") as Outlook.Application; The link below has a good example of this:

Get and sign in to an instance of Outlook