IHttpContext::GetRootContext Method

Retrieves a pointer to the root context for the current context.


virtual IHttpContext* GetRootContext(  
) const = 0;  


This method takes no parameters.

Return Value

A pointer to an IHttpContext interface.


The GetRootContext method retrieves a pointer to the IHttpContext interface for the root context of the current request. For example, if an HTTP module creates a child context by using the CloneContext method, the GetRootContext method can help determine whether the module is processing on the root context or on the child context.


When the current context is the root context, the GetRootContext method will return NULL.


The following code example demonstrates how to use the GetRootContext method to create an HTTP module that retrieves the root context for the request. The module compares the root context with NULL and the current request context to determine whether the root context is different than the current context. The module then returns a message to the Web client and exits.

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

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

        // Clear the existing response.
        // Set the MIME type to plain text.

        // Retrieve a pointer to the root context.
        IHttpContext * pRootContext = pHttpContext->GetRootContext();

        // Compare the root context and return a message to the client.
        if (pRootContext == NULL) WriteResponseMessage(
            pHttpContext, "The root context is null.");
        else if (pRootContext == pHttpContext) WriteResponseMessage(
            pHttpContext, "The current context equals the root context.");
        else WriteResponseMessage(
            pHttpContext, "The root context differs from the current context.");

        // End additional processing.

    // Create a utility method that inserts a string value into the response.
    HRESULT WriteResponseMessage(
        IHttpContext * pHttpContext,
        PCSTR pszBuffer
        // Create an HRESULT to receive return values from methods.
        HRESULT hr;
        // Create a data chunk. (Defined in the Http.h file.)
        HTTP_DATA_CHUNK dataChunk;
        // Set the chunk to a chunk in memory.
        dataChunk.DataChunkType = HttpDataChunkFromMemory;
        // Buffer for bytes written of data chunk.
        DWORD cbSent;

        // Set the chunk to the buffer.
        dataChunk.FromMemory.pBuffer =
            (PVOID) pszBuffer;
        // Set the chunk size to the buffer size.
        dataChunk.FromMemory.BufferLength =
            (USHORT) strlen(pszBuffer);
        // Insert the data chunk into the response.
        hr = pHttpContext->GetResponse()->WriteEntityChunks(
        // Test for an error.
        if (FAILED(hr))
            // Return the error status.
            return hr;

        // Return a success status.
        return S_OK;

// Create the module's class factory.
class MyHttpModuleFactory : public IHttpModuleFactory
        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 we cannot create the instance.
            // 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.
    DWORD dwServerVersion,
    IHttpModuleRegistrationInfo * pModuleInfo,
    IHttpServer * pGlobalInfo
    UNREFERENCED_PARAMETER( dwServerVersion );

    return pModuleInfo->SetRequestNotifications(
        new MyHttpModuleFactory,

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.


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
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
Product IIS 7.0, IIS 7.5, IIS Express 7.5, IIS 8.0
Header Httpserv.h

See Also

IHttpContext Interface
IHttpContext::CloneContext Method
IHttpContext::GetParentContext Method