Clickonce: Publish on IIS fails with System.Deployment.Application.DeploymentDownloadException (Unknown subtype)

<Error Log>

Below is a summary of the errors, details of these errors are listed later in the log.
    * Activation of C:\Documents and Settings\<Username>\Local Settings\Temporary Internet Files\Content.IE5\PEB6XSQC\*.application resulted in exception. Following failure messages were detected:
        + Downloading file:///C:/Documents and Settings/<username>/Local Settings/Temporary InternetFiles/Content.IE5/PEB6XSQC/<Appname>.application did not succeed.

    Following errors were detected during this operation.
    * [10/28/2008 3:00:20 PM] System.Deployment.Application.DeploymentDownloadException (Unknown subtype)
        – Downloading file:///C:/Documents and Settings/ykasan/Local Settings/Temporary Internet Files/Content.IE5/PEB6XSQC/HIC Report Launcher.application did not succeed.
        – Source: System.Deployment
        – Stack trace:
            at System.Deployment.Application.SystemNetDownloader.DownloadSingleFile(DownloadQueueItem next)
            at System.Deployment.Application.SystemNetDownloader.DownloadAllFiles()



In My case the Publish Location was \\<Servername>\c$\wwwRoot\VirtualDirectory\
This UNC path was Publishing the application on the web server under same Domain
However, when we changed the publish Location to http:\Webserver\Visrtual Directory in Place of UNC Visual studio gave Error

Failed to connect to ‘http://<Server>/<Virtual Dir>/’ with the following error: Unable to create the Web site ‘http://<Server>/<Virtual Dir>/’.  The Web server does not appear to have FrontPage Server Extensions installed.           


-Check if Web server has FrontPage Extension installed and Install it if its not installed already
-check that FrontPage extension is accessible as well

-Check that Clickonce MIME types are also set on web server

To set MIME types in the IIS root directory’s -> Properties -> HTTP Headers -> MIME Types.RightClick the Default Web Site of your IIS, then Select Properties, then go the HTTP Header tab. Near the bottom of the tab there is a command button called MIME Types
Click the MIME Types button. A New dialog pops.

Extension to .application and MIME Type to application/x-ms-application
Extension to .manifest and add MIME Type to application/x-ms-manifest 
Then add the Extension to .deploy and  add MIME Type to application/octet-stream

Please check MSDN For More information on MIME types and Clickonce Configuration.

Comments (5)

  1. Axel Arnold Bangert says:


    exactly that has been my problem too. These extensions had been missing:

    Extension to .application and MIME Type to application/x-ms-application

    Extension to .manifest and add MIME Type to application/x-ms-manifest

    Then add the Extension to .deploy and  add MIME Type to application/octet-stream

    After having made the entries it worked perfectly. I worry that I did not find the solution by myself, though

    it is obvious – how could the IIS Server process an extension, that is unknown.

    Good post!

    Axel Arnold Bangert – Herzogenrath 2011

  2. Ramon says:


    I just needed to add the MIME Types for the website in IIS.

    Worked perfectly.

  3. OMGmicrosoft says:

    Why is it called "Click once" if you have to click a zillion things different machines ?

    It should be called, "YouNeedToKnow5TechnologiesToUseThisPubhlisher" surely

    Click Once ? ( if you don't know the definition of once )

  4. Frank says:

    I use megaui.exe to change the url of clickonce, but get this error. So I use publish url directoryly, then it worked.