linQ

//分组排序 对应SQL partion by
var REList = crList.OrderByDescending(x => x.dtTime).GroupBy(x => new { x.vcRobot })//可多列
                                      .Select(g => new { g, count = g.Count() })
                                      .SelectMany(t => t.g.Select(b => new { b.vcRobot, b.dtTime }).Zip(Enumerable.Range(1, 1),//条数范围 Enumerable.Range(1, t.count)
                                      (j, i) => new { j, rownumber = i })).ToList();

// 针对list分组
var groupList = oList.GroupBy(x => x.Name).Select(x => new { Name = x.Key, list = x.ToList() });