集合分组、求和、合并字段
var newList = list.GroupBy(s => s.userId).Select(s => new person { userId = s.Key, weight = s.Sum(s => s.weight),desc=String.Join("、", s.Select(a => a.desc).ToList()) }).ToList();
var newList = list.GroupBy(s => s.userId).Select(s => new person { userId = s.Key, weight = s.Sum(s => s.weight),desc=String.Join("、", s.Select(a => a.desc).ToList()) }).ToList();
