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ihttpfileinfo-checkiffilehaschanged-method.md

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title IHttpFileInfo::CheckIfFileHasChanged Method
ms.date 10/07/2016
description IHttpFileInfo CheckIfFileHasChanged Method returns a value that indicates whether the corresponding file has been changed since it was loaded into a file cache.
ms.assetid ea91d352-6fa5-7e85-8616-f0294cbd7bd3

IHttpFileInfo::CheckIfFileHasChanged Method

Returns a value that indicates whether the corresponding file has been changed since it was loaded into a file cache.

Syntax

virtual BOOL CheckIfFileHasChanged(  
   IN HANDLE hUserToken  
) = 0;

Parameters

hUserToken
[IN] A HANDLE that contains the token for the user.

Return Value

true if the corresponding file has changed; otherwise, false.

Remarks

The behavior of the CheckIfFileHasChanged method is implementation specific. You should use the following information as a guideline, but it may not be correct in all scenarios:

  • Implementers that reference an Internet file return false.

  • Implementers that reference a non-Internet file return true if the actual file has changed or if the attributes on the file cannot be accessed.

Caution

While most implementers allow the hUserToken parameter to be NULL, you should provide a non-NULL value whenever possible because the implementation may change.

Example

The following code example demonstrates how to use the IHttpContext::GetFileInfo method to create an HTTP module that retrieves a pointer to an IHttpFileInfo interface for the current request. The example then calls the CheckIfFileHasChanged method to retrieve file change information for the requested file and displays this information to a Web client.

[!code-cppIHttpFileInfo#3]

The following text is a sample of the data output from the preceding code example.

HTTP/1.1 200 OK  
content-Type:text/plain  
Server: Microsoft-IIS/7.0  
Date: Thu, 15 Dec 2005 22:22:09 GMT  
Content-Length: 348  
  
File Changed: false

Your module must export the RegisterModule function. You can export this function by creating a module definition (.def) file for your project, or you can compile the module by using the /EXPORT:RegisterModule switch. For more information, see Walkthrough: Creating a Request-Level HTTP Module By Using Native Code.

You can optionally compile the code by using the __stdcall (/Gz) calling convention instead of explicitly declaring the calling convention for each function.

Requirements

Type Description
Client - IIS 7.0 on [!INCLUDEwinvista]
- IIS 7.5 on Windows 7
- IIS 8.0 on Windows 8
- IIS 10.0 on Windows 10
Server - IIS 7.0 on [!INCLUDEwinsrv2008]
- IIS 7.5 on Windows Server 2008 R2
- IIS 8.0 on Windows Server 2012
- IIS 8.5 on Windows Server 2012 R2
- IIS 10.0 on Windows Server 2016
Product - IIS 7.0, IIS 7.5, IIS 8.0, IIS 8.5, IIS 10.0
- [!INCLUDEiisexp75], [!INCLUDEiisexp80], [!INCLUDEiisexp100]
Header Httpserv.h

See Also

IHttpFileInfo Interface