IHttpRequest::DeleteHeader Method

Article
03/09/2018

Deletes an HTTP header from the request.

Syntax

virtual HRESULT DeleteHeader(  
   IN PCSTR pszHeaderName  
) = 0;  
  
virtual HRESULT DeleteHeader(  
   IN HTTP_HEADER_ID ulHeaderIndex  
) = 0;

Parameters

pszHeaderName
[IN] A pointer to a string that contains the name of the header to delete.

ulHeaderIndex
[IN] An HTTP_HEADER_ID value that specifies the ID of an HTTP header to delete.

Return Value

An HRESULT. Possible values include, but are not limited to, those in the following table.

Value	Description
S_OK	Indicates that the operation was successful.

Remarks

The DeleteHeader method deletes a specified HTTP header from the current request. There are two overloaded versions of the DeleteHeader method. One specifies the header by using a string that is contained in the pszHeaderName parameter. The other overload uses an unsigned long integer that is contained in the ulHeaderIndex parameter.

The header name specified by the pszHeaderName parameter can be a custom header or a header defined in Request for Comments (RFC) 1945, "Hypertext Transfer Protocol -- HTTP/1.0," or RFC 2616, "Hypertext Transfer Protocol -- HTTP/1.1."

Note

The pszHeaderName parameter cannot be set to null.

The ulHeaderIndex parameter specifies the ID of an HTTP header that is listed in the HTTP_HEADER_ID enumeration, which contains several common HTTP headers.

Note

The HTTP_HEADER_ID enumeration is defined in the Http.h header file.

Example

The following code example illustrates how to use both versions of the DeleteHeader method to create an HTTP module that removes the User-Agent and Accept-Language HTTP headers from the request.

#define _WINSOCKAPI_
#include <windows.h>
#include <sal.h>
#include <httpserv.h>

// Create the module class.
class MyHttpModule : public CHttpModule
{
public:
    REQUEST_NOTIFICATION_STATUS
    OnBeginRequest(
        IN IHttpContext * pHttpContext,
        IN IHttpEventProvider * pProvider
    )
    {
        UNREFERENCED_PARAMETER( pProvider );

        // Create an HRESULT to receive return values from methods.
        HRESULT hr;

        // Retrieve a pointer to the request.
        IHttpRequest * pHttpRequest = pHttpContext->GetRequest();

        // Test for an error.
        if (pHttpRequest != NULL)
        {
            // Delete the "User-Agent" header.
            hr = pHttpRequest->DeleteHeader("User-Agent");
            // test for an error
            if (FAILED(hr))
            {
                // Set the error status.
                pProvider->SetErrorStatus( hr );
                // End additional processing.
                return RQ_NOTIFICATION_FINISH_REQUEST;
            }
            // Delete the "Accept-language" header.
            // (Use values from HTTP_HEADER_ID in the Http.h file.)
            hr = pHttpRequest->DeleteHeader(HttpHeaderAcceptLanguage);
            // Test for an error.
            if (FAILED(hr))
            {
                // Set the error status.
                pProvider->SetErrorStatus( hr );
                // End additional processing.
                return RQ_NOTIFICATION_FINISH_REQUEST;
            }
        }

        // Return processing to the pipeline.
        return RQ_NOTIFICATION_CONTINUE;
    }
};

// Create the module's class factory.
class MyHttpModuleFactory : public IHttpModuleFactory
{
public:
    HRESULT
    GetHttpModule(
        OUT CHttpModule ** ppModule, 
        IN IModuleAllocator * pAllocator
    )
    {
        UNREFERENCED_PARAMETER( pAllocator );

        // Create a new instance.
        MyHttpModule * pModule = new MyHttpModule;

        // Test for an error.
        if (!pModule)
        {
            // Return an error if the factory cannot create the instance.
            return HRESULT_FROM_WIN32( ERROR_NOT_ENOUGH_MEMORY );
        }
        else
        {
            // Return a pointer to the module.
            *ppModule = pModule;
            pModule = NULL;
            // Return a success status.
            return S_OK;
        }            
    }

    void Terminate()
    {
        // Remove the class from memory.
        delete this;
    }
};

// Create the module's exported registration function.
HRESULT
__stdcall
RegisterModule(
    DWORD dwServerVersion,
    IHttpModuleRegistrationInfo * pModuleInfo,
    IHttpServer * pGlobalInfo
)
{
    UNREFERENCED_PARAMETER( dwServerVersion );
    UNREFERENCED_PARAMETER( pGlobalInfo );

    // Set the request notifications and exit.
    return pModuleInfo->SetRequestNotifications(
        new MyHttpModuleFactory,
        RQ_BEGIN_REQUEST,
        0
    );
}

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 Windows Vista - IIS 7.5 on Windows 7 - IIS 8.0 on Windows 8 - IIS 10.0 on Windows 10
Server	- IIS 7.0 on Windows Server 2008 - 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 Technical Preview
Product	- IIS 7.0, IIS 7.5, IIS 8.0, IIS 8.5, IIS 10.0 - IIS Express 7.5, IIS Express 8.0, IIS Express 10.0
Header	Httpserv.h

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