LINQ 删除重复项和结果项以获得数量总和

我只是想检查是否有更快的方法使用 LINQ 通过 id 从重复项中删除列表，但在结果列表项中将具有一些其他属性的总和（在本例中为价格）。例如：

起始列表：

List<Item> a = new List<Item>
{
   new Item {Id = 1, Name = "Item1", Code = "IT00001", Price = 100},
   new Item {Id = 2, Name = "Item2", Code = "IT00002", Price = 200},
   new Item {Id = 3, Name = "Item3", Code = "IT00003", Price = 150},
   new Item {Id = 1, Name = "Item1", Code = "IT00001", Price = 100},
   new Item {Id = 3, Name = "Item3", Code = "IT00003", Price = 150},
   new Item {Id = 3, Name = "Item3", Code = "IT00004", Price = 250}
};

结果列表将是：

List<Item> a = new List<Item>
{
  new Item {Id = 1, Name = "Item1", Code = "IT00001", Price = 200},
  new Item {Id = 2, Name = "Item2", Code = "IT00002", Price = 200},
  new Item {Id = 3, Name = "Item3", Code = "IT00003", Price = 550}
};

在（功能性）LINQ 中，它类似于：

List<Item> b = a
    .GroupBy(x => x.Id)
    .Select(x => new Item { Id = x.Key, Name = x.First().Name, Code = x.First().Code, Price = x.Sum(y => y.Price) })
    .ToList();

在基于关键字的 LINQ 中，它类似于：

List<Item> c = (from x in a
                group x by x.Id into y
                select new Item { Id = y.Key, Name = y.First().Name, Code = y.First().Code, Price = y.Sum(z => z.Price) }
               ).ToList();