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var result = from
a in
model join
b in
orderDetailModel on
a.FoodMenuID equals
b.FoodMenuID into
g from
b in
g.DefaultIfEmpty() select
new Model.WebApiModel.WMFoodMenu { BarginPrice = a.BarginPrice, Credits = a.Credits, FoodMenuCategoryID = a.FoodMenuCategoryID, FoodMenuID = a.FoodMenuID, RestaurantID = a.RestaurantID, FoodMenuName = a.FoodMenuName, SaleCount = b != null
? b.FoodMenuSaleCount : 0, ImgUrl100 = a.ImgUrl100, ImgUrl150 = a.ImgUrl150, IsRecommend = a.IsRecommend, Price = a.Price }; |
这里，必须要注意一点是：SaleCount = b != null ? b.FoodMenuSaleCount : 0，这里如果SaleCount字段不允许为空，必须先判定。
如果写成 SaleCount = b.FoodMenuSaleCount，当右边数据为空时，将出现未将对象引用设置对实例的错误
linq to sql 左联接出错，未将对象引用设置到实例,布布扣,bubuko.com
原文：http://www.cnblogs.com/jys509/p/3576406.html