IHttpRequest::SetHeader Method

Article
03/09/2018

Sets or appends the value of a specified HTTP request header.

Syntax

virtual HRESULT SetHeader(  
   IN PCSTR pszHeaderName,  
   IN PCSTR pszHeaderValue,  
   IN USHORT cchHeaderValue,  
   IN BOOL fReplace  
) = 0;  
  
virtual HRESULT SetHeader(  
   IN HTTP_HEADER_ID ulHeaderIndex,  
   IN PCSTR pszHeaderValue,  
   IN USHORT cchHeaderValue,  
   IN BOOL fReplace  
) = 0;

Parameters

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

ulHeaderIndex
[IN] The ID of an HTTP header to set.

pszHeaderValue
[IN] A pointer to a string that contains the value of the header to set.

cchHeaderValue
[IN] The length, in characters, of the header value, not including the \0 character.

fReplace
[IN] true to overwrite the existing header; otherwise, false.

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.
ERROR_INVALID_DATA	Indicates that the data is not valid (for example, the data in the header is too long).
ERROR_INVALID_PARAMETER	Indicates that the specified parameter is not valid (for example, the parameter is NULL).
ERROR_NOT_ENOUGH_MEMORY	Indicates that there is insufficient memory to perform the operation.

Remarks

The SetHeader method sets the value of an HTTP header for the current request. There are two overloaded versions of the SetHeader method. One enables you to specify 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.

Note

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

If the fReplace parameter is true, the specified header value will replace the existing header value if the header exists. If fReplace is false, you should append the specified header value to the existing header and separate the value from the header itself with a comma.

Example

The following code example demonstrates how to use both overloads of the SetHeader method to create an HTTP module that replaces the HTTP User-Agent and Accept-Language headers with new values.

#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;

        // Specify the "User-Agent" header name.
        char szHeaderName[] = "User-Agent";
        // Specify the "User-Agent" header value.
        char szUserAgent[] = "Test Browser";
        // Specify the "Accept-Language" header value.
        char szAcceptLanguage[] = "en-ie";

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

        // Test for an error.
        if (pHttpRequest != NULL)
        {
            // Replace the "User-Agent" header.
            hr = pHttpRequest->SetHeader(
                szHeaderName,szUserAgent,
                (USHORT)strlen(szUserAgent),true);

            // Test for an error.
            if (FAILED(hr))
            {
                // Set the error status.
                pProvider->SetErrorStatus( hr );
                // End additional processing.
                return RQ_NOTIFICATION_FINISH_REQUEST;
            }

            // Replace the "Accept-language" header.
            hr = pHttpRequest->SetHeader(
                HttpHeaderAcceptLanguage,szAcceptLanguage,
                (USHORT)strlen(szAcceptLanguage),true);

            // 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;
        }            
    }
/* MERGEFORMAT 16 Aug 07  5:41 PM */
    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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