提供的总和的委托不是predicate;这是一个选择。

The delegate provided to Sum isn't a predicate; it's a selector.

您想求和的数量属性？如果是这样，我怀疑你想要的：

Are you trying to sum the Qty property? If so, I suspect you want:

A = g.Where(c => c.Type == "A").Sum(c => c.Qty),
B = g.Where(c => c.Type == "B").Sum(c => c.Qty),
C = g.Where(c => c.Type == "C").Sum(c => c.Qty)

（或者你可以按类型组以及，当然。）

(Or you could group by type as well, of course.)