string strValue = ptrFolder->GetDetailsOf( _variant_t((IDispatch *)ptrItem), i);

這句是關鍵  IDispatch用法

#include <iostream>
#include <string>
#import <Shell32.dll>

using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
                CoInitialize(NULL);

	Shell32::IShellDispatchPtr ptrShell; 
	ptrShell.CreateInstance(__uuidof(Shell32::Shell)); 
	_variant_t var((short
 
)Shell32::ssfRECENT); 

	Shell32::FolderPtr ptrFolder = ptrShell->NameSpace("C://");

	Shell32::FolderItemPtr ptrItem = ptrFolder->ParseName("output.mp4");

	for( int i = 0; i < 10; i++ ) 
	{ 
		string strName = ptrFolder->GetDetailsOf(0, i); 
		cout << i <<strName << ":"; 
		//string strValue = ptrFolder->GetDetailsOf(ptrItem, i); 
 

		string strValue = ptrFolder->GetDetailsOf( _variant_t((IDispatch *)ptrItem), i);

		cout << strValue << endl; 
	} 

	ptrItem.Release();
	ptrFolder.Release();
	ptrShell.Release(); 

	CoUninitialize(); 
	return 0;
}