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

xibiliyaha 40 Reputation points

I am deploying my 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?

Internet Information Services
A set of technologies in the .NET Framework for building web applications and XML web services.
3,410 questions
Windows Server
Windows Server
A family of Microsoft server operating systems that support enterprise-level management, data storage, applications, and communications.
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Accepted answer
  1. Sam Wu-MSFT 7,286 Reputation points Microsoft Vendor


    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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  1. Lex Li (Microsoft) 5,312 Reputation points Microsoft Employee

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

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