Cannot add duplicate collection entry of type 'add' with unique key attribute 'test4' set to 'tagsmodule'

Question

I am deploying my asp.net application in windows server and got this error.

Config Error: Cannot add duplicate collection entry of type 'add' with unique key attribute 'test4' set to 'tagsmodule'.

Any idea how to solve this error?

Answer 1

@xibiliyaha

Since the error message mentions a duplicate record, check the web.config for identical definitions:

1. Enable Failed Request Tracing
2. Add a rule
3. If the issue occurs, check web.config file. Are there identical Failed Request Tracing rules?

If there are no duplicates, check the rules in tracing module at all application, site, and server levels in IIS Manager. Make sure there are no conflicting rules.

If the issue still persists, add the line below into web.config. It will remove all existing rules to prevent duplication.

<remove path="*" />

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Answer 2

If you configure a collection in web.config, the best way is to add a remove tag in front,

<configuration>
  <...>
    <...>
      <remove test4="tagsmodule" />
      <add test4="tagsmodule" ... />
    </...>
  </...>
</configuration>