In C ++, XMLHttpRequest asynchronously uses onreadystatuschange

First, you need to write a class to implement the idispatch interface, and then upload the class. The Code is as follows:
# Ifndef xmlhttpeventsink_h _
# Define xmlhttpeventsink_h _

# Include "MSXML. H"
# Include <winnt. h>
# Include <wtypes. h>
# Include <windows. h>

Class xmlhttpeventsink: Public idispatch
{
Public:
Xmlhttpeventsink (ixmlhttprequest * request, handle completedevent): _ refcount (1), _ Request (request), _ completedevent (completedevent)
{
// Don't increase the reference count to the request object; doing so wocould create a circular reference
// And thus a memory leak.
}
Virtual ~ Xmlhttpeventsink (){}

// Iunknown
Stdmethodimp QueryInterface (refiid riid, void ** ppvobject );
Stdmethodimp _ (ulong) addref ();
Stdmethodimp _ (ulong) release ();

// Idispatch
Stdmethodimp gettypeinfocount (uint * pctinfo );
Stdmethodimp gettypeinfo (uint itinfo, lcid, itypeinfo ** pptinfo );
Stdmethodimp getidsofnames (refiid riid, lpolestr * rgsznames, uint cnames, lcid, dispid * rgdispid );
Stdmethodimp invoke (dispid dispidmember, refiid riid, lcid, word wflags, dispparams * pdispparams, variant * pvarresult, interval info * p1_info, uint * puargerr );
PRIVATE:
Long _ refcount;
Ixmlhttprequest * _ request;
Handle _ completedevent;
};

# Endif
-============================================== ====================
# Include "xmlhttpeventsink. H"

Stdmethodimp xmlhttpeventsink: QueryInterface (const IID & riid, void ** ppvobject)
{
If (ppvobject = NULL)
Return e_invalidarg;

* Ppvobject = NULL;

If (riid = iid_iunknown)
* Ppvobject = static_cast <iunknown *> (this );
Else if (riid = iid_idispatch)
* Ppvobject = static_cast <idispatch *> (this );

If (* ppvobject = NULL)
Return e_nointerface;

Addref ();

Return s_ OK;
}

Stdmethodimp _ (ulong) xmlhttpeventsink: addref ()
{
Return interlockedincrement (& _ refcount );
}

Stdmethodimp _ (ulong) xmlhttpeventsink: release ()
{
Long refcount = interlockeddecrement (& _ refcount );
If (refcount = 0)
{
Delete this;
Return 0;
}
Else
Return refcount;
}

Stdmethodimp xmlhttpeventsink: gettypeinfocount (uint * pctinfo)
{
Return e_notimpl;
}

Stdmethodimp xmlhttpeventsink: gettypeinfo (uint itinfo, lcid, itypeinfo ** pptinfo)
{
Return e_notimpl;
}

Stdmethodimp xmlhttpeventsink: getidsofnames (const IID & riid, lpolestr * rgsznames, uint cnames, lcid, dispid * rgdispid)
{
Return e_notimpl;
}

Stdmethodimp xmlhttpeventsink: invoke (dispid dispidmember, const IID & riid, lcid, word wflags, dispparams * handle, variant * pvarresult, interval info * p1_info, uint * puargerr)
{
// Since this class isn't used for anything else, invoke will get called only for onreadystatechange, and
// Dispidmember will always be 0.

Long state;
// Retrieve the state
_ Request-> get_readystate (& State );
If (State = 4)
{
// The request has completed.
// Get the Request status.
Long status;
_ Request-> get_status (& status );

If (status = 200)
{
// Get the response body if we were successful.
BSTR body;
_ Request-> get_responsetext (& Body );
}

// Signal the main thread we're done.
Setevent (_ completedevent );
}
Return s_ OK;
}
-============================================== ================
Call code:
Coinitialize (null );
Ixmlhttprequest * prequest = getxmlhttp ();

Prequest-> setRequestHeader (L "Content-Type", l "text/XML ");
Prequest-> setRequestHeader ("soapaction", "http://schemas.microsoft.com/exchange/services/2006/messages/FindItem ");
Widestring url = l "http://mail.pudong.sh/ews/exchange.asmx ";

Tagvariant account;
Account. Vt = vt_bstr;
Account. bstrval = l "MailAdmin@pudong.sh ";

Tagvariant password;
Password. Vt = vt_bstr;

Password. bstrval = l "app1234 ";
Tagvariant basync;
Basync. Vt = vt_bool;
Basync. boolval = false;

Widestring datastr = l "";
Tagvariant data;
Data. Vt = vt_bstr;
Data. bstrval = datastr. c_bstr ();

Handle completedevent = createevent (null, false, false, null );
Prequest-> open (L "Post", URL. c_bstr (), basync, account, password );

Idispatch * sink = new xmlhttpeventsink (prequest, completedevent );
Prequest-> put_onreadystatechange (sink );
Prequest-> send (data );

Sink-> release ();
Prequest-> release ();

Waitforsingleobject (completedevent, infinite );
Closehandle (completedevent );

Couninitialize ();