Linq多对多查询

2013-09-08

Linq多对多查询求救我这个需求是多对多菜品和菜品分类要根据菜品分类查出所有菜品信息（包括菜品分类）就

Linq多对多查询求救
我这个需求是多对多菜品和菜品分类要根据菜品分类查出所有菜品信息（包括菜品分类）就是确定一条分类然后还要再加到查出每个菜品所有分类（这里的分类不止一个）代码如下：

var q = db.foodcategories.First(fc => fc.Id == categoryId);

             var q_a = from qq in q.foods
                       from p in db.pictures
                       //from qfc in q_fc
                       where p.FoodId==qq.Id
                       select new FoodModel
                       {
                           Id = qq.Id,
                           Name = qq.Name,
                           pictureUrl=p.Url,
                           Price = qq.Price,
                           Description = qq.Description,
                           MainIngredient = qq.MainIngredient,
                           MinorIngredient = qq.MinorIngredient,
                           Flavoring = qq.Flavoring,
                           Discount = qq.Discount,
                           Recommended = qq.Recommended

,foodCategories = qq.foodcategories.Select(fc => new FCategoryModel { Name = fc.Name }).AsQueryable()
};

这样写会出现以下异常:There is already an open DataReader associated with this Connection which must be closed first. 求助解决方案没有分了求大神帮忙，在线等急急急 asp.net? linq asp.net 多对多
[解决办法]
这个提示说明你用到了DataReader但是没有正确关闭。和Linq无关。
[解决办法]
试试

var q = db.foodcategories.First(fc => fc.Id == categoryId);
var q_a = from qq in q.foods
                       join p in db.pictures on qq.Id equals p.FoodId
                       select new FoodModel
                       {
                           Id = qq.Id,
                           Name = qq.Name,
                           pictureUrl=p.Url,
                           Price = qq.Price,
                           Description = qq.Description,

                           MainIngredient = qq.MainIngredient,
                           MinorIngredient = qq.MinorIngredient,
                           Flavoring = qq.Flavoring,
                           Discount = qq.Discount,
                           Recommended = qq.Recommended,
                           foodCategories = qq.foodcategories.Select(fc => new FCategoryModel { Name = fc.Name }).AsQueryable()
                       };

[解决办法]

引用:

Quote: 引用:

试试

                           Description = qq.Description,
                           MainIngredient = qq.MainIngredient,
                           MinorIngredient = qq.MinorIngredient,
                           Flavoring = qq.Flavoring,
                           Discount = qq.Discount,
                           Recommended = qq.Recommended,
                           foodCategories = qq.foodcategories.Select(fc => new FCategoryModel { Name = fc.Name }).AsQueryable()
                       };

谢谢大神指教，能说明为什么这样就行，我那个就不行么？

我估计是inner join引起的吧，你没写对，注意要对应，你可以测试一下，看看，顺便回馈我一下，
var q_a = from qq in q.foods
join p in db.pictures on qq.Id equals p.FoodId

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