"clickonce cannot download the application. the application is missing required files. contact application vendor for assistance"

N. Mark Graves 6 Reputation points
2021-06-04T00:32:59.47+00:00

This is Visual Studio 2017.

Are there any plans to fix this issue, or document a workaround? Is ClickOnce no longer supported?

dotnet-csharp is the wrong tag, but I'm required to enter a tag, and there's no tag for ClickOnce.

C#
C#
An object-oriented and type-safe programming language that has its roots in the C family of languages and includes support for component-oriented programming.
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  1. Daniel Zhang-MSFT 9,611 Reputation points
    2021-06-04T01:38:39.493+00:00

    Hi NMarkGraves,
    This error occurs when one or more files listed in the application manifest cannot be found on the server. You can open the application manifest in a text editor and verify that you have uploaded all relevant files for deployment.
    You can also try to clear the clickonce cache and reinstall.
    And here some related documents you can refer to.
    How to: Set a Custom Log File Location for ClickOnce Deployment Errors
    Troubleshooting Specific Errors in ClickOnce Deployments
    Best Regards,
    Daniel Zhang


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  2. Tim R 1 Reputation point
    2021-08-05T14:03:38.723+00:00

    I have been deploying WinForms applications using ClickOnce for 15 years. I am getting the same error when using Edge v92. Our networking team has enabled ClickOnce for Edge in Group Policy (see RSOP screencapture) but Edge is nonetheless trapping the setup.exe when the user clicks the "Run" button on the web page that is deployed by Visual Studio to the UNC path. The user must click on the [...] button and choose "keep" (see screen capture). Then, when the user clicks on the downloaded setup.exe file, the installation is terminated with the error reported by the original poster above, and when the Details button is clicked, the details show that the ClickOnce installer was looking for the app.application file in the Downloads folder and not finding it there. So this would appear to be the SmartScreen security interfering with ClickOnce. Edge is still downloading the file as a "normal download" rather than as an application to be installed. How to stop that interference so that ClickOnce can proceed?

    System.IO.FileNotFoundException
    Could not find file 'C:\Users\foo\Downloads\TestApp.application'.

    120805-capture.png

    120881-rsop75.png

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