Group into a dictionary of elements

Hi I have a list of element of class type class1 as show below. How do I group them into a

Dictionary<int,List<SampleClass>> based on the groupID

class SampleClass
{
   public int groupID;
   public string someData;
 }                                                                                  

I have done this way:

var t =(from data in datas group data by data.groupID into dataGroups select dataGroups).ToDictionary(gdc => gdc.ToList()[0].groupID, gdc => gdc.ToList());

Is there a better way of doing thiss