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ihttpcachekey-gethash-method.md

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title IHttpCacheKey::GetHash Method
description Describes the IHttpCacheKey::GetHash method and details its syntax, parameters, return value, remarks, code example, and requirements.
ms.date 10/07/2016
ms.assetid 4dbfc063-f7f7-d86d-f19e-2451bf72f70f

IHttpCacheKey::GetHash Method

Returns the unique hash code of an item in the global cache.

Syntax

virtual DWORD GetHash(  
   VOID  
) const = 0;

Parameters

This method takes no parameters.

Return Value

A DWORD that represents the unique hash code of an item in the global cache.

Remarks

CGlobalModule derived classes that register for GL_CACHE_OPERATION events receive an ICacheProvider pointer as a parameter on the CGlobalModule::OnGlobalCacheOperationvirtual method. You can retrieve an IHttpCacheKey pointer by calling the ICacheProvider::GetCacheKey method on the ICacheProvider pointer. You can then retrieve the hash code of the item involved in the cache operation by calling the GetHash method on the IHttpCacheKey pointer.

The GetHash return value depends on both interface and implementation. For example, implementers of the IFileKey, IHttpTokenKey, and IUriKey interfaces all use different hashing algorithms based upon the data that they hold.

Example

The following code example demonstrates how to create a global module that listens for GL_CACHE_OPERATION and GL_CACHE_CLEANUP events and then writes the IHttpCacheKey and the hash information to the Event Viewer.

Caution

[!INCLUDEiisver] generates a large number of events in the Event Viewer. To avoid a log overflow error in a production environment, you should generally avoid writing cache information to the event log. For demonstration purposes, this code example writes an entry to the Event Viewer in debug mode only.

[!code-cppIHttpCacheKey#3]

The above code writes a new event to the Event Viewer, where the Data box contains a string similar to the following.

IHttpCacheKey::GetHash: 46

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

IHttpCacheKey Interface