Here is an old post from our good friend, Steve Pilon:
You can get access to data for a collection of PI Points through the PointList object - more specifically it's Data property, which returns a ListData object. You can get a PointList by manually building it (PointList.Add) or from a Server.GetPoints or Server.GetPointsSQL call.
However you should note that some of the ListData methods are not implemented in the current version of the PI SDK, e.g. RecordedValues. The Snapshot property and the ArcValue method (which returns values for the list of points, at one particular timestamp) are implemented. More information can be found in the PI SDK Programming Reference.
Hope that helps you get started in the right direction...
There are a number of discussions on similar questions before, you can easily find these threads by searching for the keyword "PointList" or "ListData" in this website as well.