Outlook VSTO Add in referencing .vsto file on a network share RRS feed

  • Question

  • Hi all,

    I've created a VSTO Outlook addin wich runs fine.

    However, since we are working on a Citrix system, if I have some small modifications to deploy, I always have to ask (and wait for) the network admin to install this on the Citrix image.

    So I thought it would be handier if I could have my addin referencing a vsto file on a network share instead of the local drive.

    Since I have a registry key named "Manifest" with the path of my vsto file, maybe I could just change this.
    (On the internet I found that UNC paths should work for the Manifest registry key, but couldn't find any more about it.)

    So I changed the value "file:///C:/folder/MyAddIn.vsto|vstolocal" into "file://///server/share/MyAddIn.vsto|vstolocal"

    However, if I change this I get a CannotCreateCustomizationDomainException saying that the vsto file is marked as not trusted.

    Anyone who knows how I can make it trusted or how I could solve this ?

    Thanks in advance.

    Friendly regards,

    Friday, June 26, 2020 2:18 PM

All replies

  • Frederick,

    Office (nor VSTO) doesn't support placing add-ins on network shares. You must install your add-in to the local folder, for example, the Program Files folder.

    profile for Eugene Astafiev at Stack Overflow, Q&A for professional and enthusiast programmers

    Friday, June 26, 2020 7:34 PM
  • Hi Eugene,

    The addin is currently placed within the program files directory but for now that’s a bad location because we are working on a Citrix environment.

    Every night, all Citrix servers reboot and are restored to the latest Citrix image. So the program files directory is also restored. If I would have updated my addin files, then they are returned back to the previous version.

    So for every minor change I have, I need the administrator to create an install a new Citrix Image. This can take a few days, so a “quick fix” isn’t possible.

    If putting it outside the local system isn’t possible, then perhaps I need some kind of self-update system.

    Do you have experience with some kind of system ?

    Another (and final) option would be to use a script which copies the files at logon/startup …

    Friendly regards,


    Tuesday, June 30, 2020 7:47 AM
  • Frederick,

    You must ask an administrator to include the add-in to the OS image.

    profile for Eugene Astafiev at Stack Overflow, Q&A for professional and enthusiast programmers

    Tuesday, June 30, 2020 1:19 PM
  • Hi Eugene,

    Yes, I know, that is how it works today.

    The problem is that the administrator isn't creating an OS image every day.

    So if I have some modifications, I have to wait untill he creates one.

    That way, I'm not able to install bug fixes or updates whenever I want.

    That's the reason I would like to put the addin OUTSIDE the OS, so it wouldn't need to be included in the image, and I could update my assemblies whenever I wanted.

    Friendly regards,



    Wednesday, July 1, 2020 9:10 AM