How to get ITimeTrigger interface for a Task Scheduler task? - c++

Question

I'm trying to get the "random delay" value for an arbitrary task scheduler task. I came up with the following C++ code:
//IRegisteredTask* pRegisteredTask for task:
// Name: "Regular Maintenance"
// Folder: "\Microsoft\Windows\TaskScheduler"
ITaskDefinition* pTaskDef = NULL;
HRESULT hr = pRegisteredTask->get_Definition(&pTaskDef);
if(SUCCEEDED(hr))
{
//Get triggers
ITriggerCollection* pTriggerCol = NULL;
hr = pTaskDef->get_Triggers(&pTriggerCol);
if(SUCCEEDED(hr))
{
//Get number of triggers
LONG nTriggerCnt = 0;
hr = pTriggerCol->get_Count(&nTriggerCnt);
if(SUCCEEDED(hr))
{
//Look through all triggers
for(LONG t = 0; t < nTriggerCnt; t++)
{
ITrigger* pTrigger = NULL;
hr = pTriggerCol->get_Item(t + 1, &pTrigger);
if(SUCCEEDED(hr))
{
//Get time trigger interface
ITimeTrigger *pTimeTrigger = NULL;
hr = pTrigger->QueryInterface(IID_ITimeTrigger, (void**)&pTimeTrigger);
if(SUCCEEDED(hr))
{
BSTR bstrRndDelay = NULL;
hr = pTimeTrigger->get_RandomDelay(&bstrRndDelay);
if(SUCCEEDED(hr))
{
//Check random delay
}
SysFreeString(bstrRndDelay);
}
else
{
//0x80004002 (E_NOINTERFACE) error happens here
}
if(pTimeTrigger)
pTimeTrigger->Release();
}
if(pTrigger)
pTrigger->Release();
}
}
}
if(pTriggerCol)
pTriggerCol->Release();
}
if(pTaskDef)
pTaskDef->Release();
I'm testing the code snippet above on the task that I know has "random delay" set up, i.e., \Microsoft\Windows\TaskScheduler->Regular Maintenance on my Windows 8.1:
but for some reason when I try to get the ITimeTrigger interface I'm getting error 0x80004002 or E_NOINTERFACE (as I marked in the code above.)
Any idea what am I doing wrong?

Answer 1

For accessing Random delay in Task scheduler, we can't do it directly you have to access by all interfaces.
For suppose I am using IDailyTigger or IWeeklyTigger Interface from this you have to access random delay.
IWeeklyTigger* lpWeeklyTrigger;
lpWeeklyTrigger->get_RandomDelay(&lcRandomDelay);
IDailyTigger* lpDailyTrigger;
lpDailyTrigger->get_RandomDelay(&lcRandomDelay);
This way you have to do for each trigger.