Unable to cast COM object of type 'Microsoft.Office.Interop.Outlook.ApplicationClass' {00063001-0000-0000-C000-000000000046} HRESULT: 0x80040155

Question

I'm having an issue with a very simple piece of C# .NET code which should (for now) simply retrieve the version number of Office installed on the computer running a WinForms application:

var oApp = new Outlook.ApplicationClass();
var outlookVersionString = oApp.Version;

It instantiates the object correct, however when I try and access the Version property, I get the following:

{"Unable to cast COM object of type 'Microsoft.Office.Interop.Outlook.ApplicationClass' to interface type 'Microsoft.Office.Interop.Outlook._Application'. This operation failed because the QueryInterface call on the COM component for the interface with IID '{00063001-0000-0000-C000-000000000046}' failed due to the following error: Interface not registered (Exception from HRESULT: 0x80040155)."}

I've done a lot of searching online, so a run-through of what I've tried:

1. Checking that in [HKEY_CLASSES_ROOT\TypeLib\{00062FFF-0000-0000-C000-000000000046}] only one Key exists ( 9.6 )
2. Checking that this ClassID and version matches in [HKEY_CLASSES_ROOT\Interface\{00063001-0000-0000-C000-000000000046}]
3. Registering MSOUTL.OLB with C:\Windows\Microsoft.NET\Framework64\v4.0.30319\regtlibv12.exe "C:\Program Files (x86)\Microsoft Office\root\Office16\MSOUTL.OLB" (fails because regtlibv12.exe isn't shipped with VS2017)
4. Downloading regtlibv12.exe and trying again (fails because 'This app can't run on your PC').
5. Running C:\Users\uczms>c:\Windows\Microsoft.NET\Framework64\v4.0.30319\regasm.exe /TLB "C:\Program Files (x86)\Microsoft Office\root\Office16\MSOUTL.OLB" (fails because it is not a valid .NET Assembly )
6. Running C:\Users\uczms>c:\Windows\Microsoft.NET\Framework64\v2.0.50727\regasm.exe /TLB "C:\Program Files (x86)\Microsoft Office\root\Office16\MSOUTL.OLB" (fails because it is not a valid .NET Assembly )
7. Using what worked with the old Interop libraries (edit: note, this does not appear to work with our Office 2016 desktops), which is a subtle change:

var oApp = new Outlook.Application(); var outlookVersionString = oApp.Version;

It might be worth noting that I have a clean Windows 10 Enterprise N Creators Update, and Office 2016 / 365 ProPlus, haven't had any previous versions installed, and haven't downgraded.

I'm not normally a desktop app developer so while I grasp some of these library registration tools, I'm by no means an expert..

Answer 1

Try to "repair" your Microsoft Office installation. Go to Programs and Features, select Modify and then Repair Online. I had the same issue and this fixed it.

Answer 2

Some my customers had a similar issues on some PC and the only action that have solved was usign the point 3 "Ensure MSOUTL.LIB is Registered" of this fantastic guide webmakers - Interface not registered (Exception from HRESULT: 0x80040155) – Microsoft Office/Outlook Error , after checked the previous point, obviously. Thanks to Jatin-Auckland for a clear and step by step guide.

Goodluck ;)

Answer 3

I appreciate this is an old topic, my issue was Visual Studio defaulting to 'Prefer 32-bit' in the project's compile properties for .NET Framework 4.5+. Screenshot of Visual Studio Prefer 32-bit checkbox