How to attach to a already running process noninvasively

Question

I have a process suspended at breakpoint under visual studio debugger. I can attach as many as cdb (Microsoft's console debugger) in non-invasive mode as

cdb -p pid -pvr

How to achieve the same using my own program which uses Debug Engine API.

 IDebugClient* debugClient = 0;
(DebugCreate( __uuidof(IDebugClient), (void **)&debugClient );
 debugClient->AttachProcess(0,id,DEBUG_ATTACH_NONINVASIVE
                |DEBUG_ATTACH_NONINVASIVE_NO_SUSPEND);

This code causes E_INVALIDARG. Is this combination is not allowed ? The one below works, but when it calls GetStackTrace, it returns E_UNEXPECTED.

debugClient->AttachProcess(0,id,DEBUG_ATTACH_NONINVASIVE);
debugControl->GetStackTrace(0, 0, 0, pStackFrames, maxFrames, &framesFilled);

I am interested to attach to a process already at debug break noninvasive way , and get a few local variable from its current stack & some global variable value.

Secondly, can someone point me the function used to dump the content of memory for a symbol iteratively like !stl does. I need to write a plugin to dump one of my vector like structure.

Thanks