C# Linq to Entity Lamda方式分组并求和求平均值

1、单字段分组并求和：

var list = data.GroupBy(g => g.GoodsId).Select(e => new { GoodsId = e.Key, Qty = e.Sum(q => q.Qty) });

2、多字段分组求和：

var list = data.GroupBy(g => new { g.StorageId,g.GoodsId }).Select(e => new { GoodsId = e.Key, Qty = e.Sum(q => q.Qty) });

求平均值直接把Sum更换成：Average即可。

3、具有导航属性的类求和及分组：

var list = data.GroupBy(g => new { g.StorageId,g.GoodsId }).Select(e => new {
                    StorageName = e.Select(i => i.Storage.Name).FirstOrDefault(),
                    GoodsName = e.Select(i => i.Goods.Name).FirstOrDefault(),                   
                    CategoryName = e.Select(i => i.Goods.CategoryName).FirstOrDefault(),
                    Qty = e.Average(q => q.Qty) });