Dirtied plug still has the old value during setDependentsDirty()

[superhuman1]

When I dirty an input plug for example mFileAttr, the setDependentsDirty() gets properly invoked, but the value of fileName plug is still the old value! I only see it getting updated once it goes through compute(). How can I access the new value in setDependentsDirty() function since it's indeed triggered by the plug value update?

MStatus FNode::setDependentsDirty(const MPlug& plug, MPlugArray& plugArray) {
if (plug == mFileAttr)
{
MString fileName = plug.asString();
}
return MPxNode::setDependentsDirty(plug, plugArray); }

Any help would be appreciated.