how to solve Error cannot add duplicate collection entry of type add with unique key attribute value in iis 7

Question

I created a asp net website and published it in iis 7  I deleted the default website option in the iis 7 and created the new website in the iis 7  When i click the default document I got the error like  Error cannot add duplicate collection entry of type add with unique key attribute  value  set to index aspx   I used the following code in my web config file     lt  xml version  1 0   gt  lt configuration gt   lt configSections gt       lt sectionGroup name  system web extensions  type  System Web Configuration SystemWebExtensionsSectionGroup  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  gt           lt sectionGroup name  scripting  type  System Web Configuration ScriptingSectionGroup  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  gt               lt section name  scriptResourceHandler  type  System Web Configuration ScriptingScriptResourceHandlerSection  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  requirePermission  false  allowDefinition  MachineToApplication   gt               lt sectionGroup name  webServices  type  System Web Configuration ScriptingWebServicesSectionGroup  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  gt                   lt section name  jsonSerialization  type  System Web Configuration ScriptingJsonSerializationSection  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  requirePermission  false  allowDefinition  Everywhere   gt                   lt section name  profileService  type  System Web Configuration ScriptingProfileServiceSection  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  requirePermission  false  allowDefinition  MachineToApplication   gt                   lt section name  authenticationService  type  System Web Configuration ScriptingAuthenticationServiceSection  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  requirePermission  false  allowDefinition  MachineToApplication   gt                   lt section name  roleService  type  System Web Configuration ScriptingRoleServiceSection  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  requirePermission  false  allowDefinition  MachineToApplication   gt               lt  sectionGroup gt           lt  sectionGroup gt       lt  sectionGroup gt   lt  configSections gt   lt appSettings  gt   lt connectionStrings  gt   lt system web gt       lt  --          Set compilation debug  true  to insert debugging          symbols into the compiled page  Because this          affects performance  set this value to true only          during development      -- gt       lt compilation debug  true  gt           lt assemblies gt               lt add assembly  System Core  Version 3 5 0 0  Culture neutral  PublicKeyToken B77A5C561934E089   gt               lt add assembly  System Data DataSetExtensions  Version 3 5 0 0  Culture neutral  PublicKeyToken B77A5C561934E089   gt               lt add assembly  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt               lt add assembly  System Xml Linq  Version 3 5 0 0  Culture neutral  PublicKeyToken B77A5C561934E089   gt                lt add assembly  System Web Extensions Design  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt               lt add assembly  System Design  Version 2 0 0 0  Culture neutral  PublicKeyToken B03F5F7F11D50A3A   gt               lt add assembly  System Windows Forms  Version 2 0 0 0  Culture neutral  PublicKeyToken B77A5C561934E089   gt  lt  assemblies gt       lt  compilation gt       lt  --         The  lt authentication gt  section enables configuration          of the security authentication mode used by          ASP NET to identify an incoming user       -- gt       lt authentication mode  Windows   gt       lt  --         The  lt customErrors gt  section enables configuration          of what to do if when an unhandled error occurs          during the execution of a request  Specifically           it enables developers to configure html error pages          to be displayed in place of a error stack trace        lt customErrors mode  RemoteOnly  defaultRedirect  GenericErrorPage htm  gt           lt error statusCode  403  redirect  NoAccess htm    gt           lt error statusCode  404  redirect  FileNotFound htm    gt       lt  customErrors gt      -- gt       lt pages gt           lt controls gt               lt add tagPrefix  asp  namespace  System Web UI  assembly  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt               lt add tagPrefix  asp  namespace  System Web UI WebControls  assembly  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt           lt  controls gt       lt  pages gt       lt httpHandlers gt           lt remove verb     path    asmx   gt           lt add verb     path    asmx  validate  false  type  System Web Script Services ScriptHandlerFactory  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt           lt add verb     path    AppService axd  validate  false  type  System Web Script Services ScriptHandlerFactory  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt           lt add verb  GET HEAD  path  ScriptResource axd  type  System Web Handlers ScriptResourceHandler  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35  validate  false   gt       lt  httpHandlers gt       lt httpModules gt           lt add name  ScriptModule  type  System Web Handlers ScriptModule  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt       lt  httpModules gt   lt  system web gt   lt system codedom gt       lt compilers gt           lt compiler language  c  cs csharp  extension   cs  warningLevel  4  type  Microsoft CSharp CSharpCodeProvider  System  Version 2 0 0 0  Culture neutral  PublicKeyToken b77a5c561934e089  gt               lt providerOption name  CompilerVersion  value  v3 5   gt               lt providerOption name  WarnAsError  value  false   gt           lt  compiler gt       lt  compilers gt   lt  system codedom gt   lt  --      The system webServer section is required for running ASP NET AJAX under Internet     Information Services 7 0   It is not necessary for previous version of IIS  -- gt   lt system webServer gt       lt validation validateIntegratedModeConfiguration  false   gt       lt modules gt           lt remove name  ScriptModule   gt           lt add name  ScriptModule  preCondition  managedHandler  type  System Web Handlers ScriptModule  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt       lt  modules gt       lt handlers gt           lt remove name  WebServiceHandlerFactory-Integrated   gt           lt remove name  ScriptHandlerFactory   gt           lt remove name  ScriptHandlerFactoryAppServices   gt           lt remove name  ScriptResource   gt           lt add name  ScriptHandlerFactory  verb     path    asmx  preCondition  integratedMode  type  System Web Script Services ScriptHandlerFactory  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt           lt add name  ScriptHandlerFactoryAppServices  verb     path    AppService axd  preCondition  integratedMode  type  System Web Script Services ScriptHandlerFactory  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt           lt add name  ScriptResource  preCondition  integratedMode  verb  GET HEAD  path  ScriptResource axd  type  System Web Handlers ScriptResourceHandler  System Web Extensions  Version 3 5 0 0  Culture neutral  PublicKeyToken 31BF3856AD364E35   gt       lt  handlers gt   lt defaultDocument gt     lt files gt       lt remove value  default aspx    gt       lt remove value  index html    gt       lt remove value  iisstart htm    gt       lt remove value  index htm    gt       lt remove value  Default asp    gt       lt remove value  Default htm    gt       lt add value  index aspx    gt     lt  files gt   lt  defaultDocument gt   lt security gt     lt requestFiltering gt       lt requestLimits maxQueryString  5120   gt     lt  requestFiltering gt   lt  security gt   lt  system webServer gt   lt runtime gt       lt assemblyBinding xmlns  urn schemas-microsoft-com asm v1  gt           lt dependentAssembly gt               lt assemblyIdentity name  System Web Extensions  publicKeyToken  31bf3856ad364e35   gt               lt bindingRedirect oldVersion  1 0 0 0-1 1 0 0  newVersion  3 5 0 0   gt           lt  dependentAssembly gt           lt dependentAssembly gt               lt assemblyIdentity name  System Web Extensions Design  publicKeyToken  31bf3856ad364e35   gt               lt bindingRedirect oldVersion  1 0 0 0-1 1 0 0  newVersion  3 5 0 0   gt           lt  dependentAssembly gt       lt  assemblyBinding gt   lt  runtime gt      Can anyone able help for that means its will really useful for my project   Thank you

User · Answer

Remove element should clear out such errors. The reason behind this is the inherited settings. Your application will inherit some settings from its parent's config file and machine's (server) config files.
You can either remove such duplicates with the remove tag before adding them or make these tags non-inheritable in the upper level config files.

User · Answer

IIS7 defines a defaultDocument section in its configuration files which can be found in the   WinDir  System32 InetSrv Config folder  Most likely  the file index aspx is already defined as a default document in one of IIS7 s configuration files and you are adding it again in your web config   I suspect that removing the line  lt add value  index aspx    gt    from the defaultDocument files section will fix your issue    The defaultDocument section of your config will look like    lt defaultDocument gt     lt files gt       lt remove value  default aspx    gt       lt remove value  index html    gt       lt remove value  iisstart htm    gt       lt remove value  index htm    gt       lt remove value  Default asp    gt       lt remove value  Default htm    gt     lt  files gt   lt  defaultDocument gt    Note that index aspx will still appear in the list of default documents for your site in the IIS manager   For more information about IIS7 configuration  click here

User · Answer

All you need is a  lt clear   gt  tag  Here s an example    lt configuration gt     lt system webServer gt       lt defaultDocument gt         lt files gt           lt clear   gt           lt add value  default aspx    gt         lt  files gt       lt  defaultDocument gt     lt  system webServer gt   lt  configuration gt

User · Answer

I got the same error and when I unknowingly removed all the default pages of the DefaultAppPool itself   Resolution  I have clicked the DefaultAppPool and opened the Default Document  Then clicked on the Revert to Parent link on the Actions pane  The default documents have came again  and thus it solves the issue  I m not sure this is the best way  but this one was the error which I have just met and hope to share with you  I hope this may help some one

User · Answer

Just keep the following in mind    In IIS if you have a folder for example called Pages with multiple websites in it  Website will inherit settings from the web config file from the parent directory  So even if the folder page  in this example Pages  isn t a website but contains a web config file  all websites listed inside of it will inherit the setting

User · Answer

For me in windows server 2012 R2 I solved it by removing the duplicates from web config file i found this line duplicated twice i removed one line and kept the other line    lt add name  CrystalImageHandler aspx GET  verb  GET  path  CrystalImageHandler aspx  type  CrystalDecisions Web CrystalImageHandler  CrystalDecisions Web  Version 13 0 4000 0  Culture neutral  PublicKeyToken 692fbea5521e1304  preCondition  integratedMode   gt  lt  handlers gt  lt validation validateIntegratedModeConfiguration  false   gt

User · Answer

The ideal scenario is to have  lt add value  default aspx    gt  in config so the application can be deployed to any server without having to reconfigure  IMHO I think the implementation within IIS is poor    We ve used the following to make our default document setup more robust and as a result more SEO friendly by using canonical URL s    lt configuration gt     lt system webServer gt       lt defaultDocument gt         lt files gt           lt remove value  default aspx    gt           lt add value  default aspx    gt         lt  files gt       lt  defaultDocument gt     lt  system webServer gt   lt  configuration gt    Works OK for us

[c#] how to solve Error cannot add duplicate collection entry of type add with unique key attribute 'value' in iis 7

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