There was an error while performing this operation. Details: Exception from HRESULT: 0xC00CEF03

Question

I have a server in windows server 2008, it has been working normally, but after I upgraded it to 2016, I ran my website again, and this error appeared:

There was an error while performing this operation. Details: Exception from HRESULT: 0xC00CEF03

Answer 1

@exwsx

0xC00CEF03 error code translates to WR_E_NSPREFIXWITHEMPTYNSURI which refers to "Writer: It is not allowed to declare a namespace prefix with empty URI"(Reference).

This error occurs when there is something wrong with the web.config file. It’s probably corrupted or there are incompatible tags and parameters. As a result of this corruption and incompatibility, IIS is not able to read this file. Therefore, it can’t make a change.

The issue mostly happens after migration because a piece of configuration that works in the older version of IIS (and .NET Framework) probably became unsupported in the newer version.

Solution for the 0xC00CEF03 error is find what part of the web.config is causing the issue is to remove sections one by one and test.

More information you can refer to this link.

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Answer 2

Upgrading from Server 2008 to Server 2016 isn't supported. You would have had to set up a new server or wipe the old server and install clean. Therefore any dependencies your app had would need to be installed on that machine. Unfortunately there isn't enough information here for us to diagnose the issue.

One thing that comes to mind at this point is that your old app would have been x86 most likely. Server 2016 is x64 only so your app is now running on x64 and that would break any native components you rely on that were x86. To eliminate this as an issue you should configure the app pool to be x86 only for now. Then ensure your app can run as x64.

Another common issue is that app pools changed between server versions. In newer versions app pools run in their own user context, limited for security reasons and by default don't load user profiles. All this can break a legacy app. Ensure your app pool has the necessary permissions to do its work and try enabling the load profile option in the app pool. This tends to resolve issues with getting things like certificates.

The error code itself indicates a bad URI path and that tends to point to web.config. Open the site in MMC and see if you get any errors in the UI. If you do then your config is bad and needs to be fixed. It could be a simple matter of missing components. For example if your app is a .NET 4.x app then you need to ensure you have installed the ASP.NET 4.x feature on the server. You may need to install a newer .NET framework version based upon your app needs. Also ensure that your app pool is configured to use managed code. You should compare your old server configuration to the new server configuration.

The Event Viewer may have some additional error information to look at as well.