c# – 以列表形式获取子集合

我有一个LINQ to EF查询,它以类的形式返回数据.该课程有一个List< RecipeCategories>我需要填充的财产. RecipeCategories表是Recipe表和RecipeCategories表之间的关系表,可以是多对多.我找到了足够的信息来获取编译代码,但是它在运行时出错并且我无法弄清楚如何正确实现.

ri = (from r in recipeData.Recipes
              where r.ID == recipeId
              select new RecipeItem
              {
                  Id = r.ID,ProductId = r.Product.ID,RecipeName = r.recipeName,RecipeDescription = r.recipeDescription,Servings = r.servings.HasValue ? r.servings.Value : 0,CreatedDate = r.createdDate,PrepTime = r.prepTime.HasValue ? r.servings.Value : 0,CookTime = r.cookTime.HasValue ? r.servings.Value : 0,Approved = r.approved,RecipeInstructions = r.recipeInstructions,RecipeIngredients = r.recipeIngredients,RecipeCategories = r.RecipeCategories.Select(i => new RecipeCategoryItem { Id = i.ID,CategoryName = i.categoryName }).ToList()
              }).First();

这是我得到的错误.

LINQ to Entities does not recognize the method ‘System.Collections.Generic.List1[RecipeCategoryItem] ToList[RecipeCategoryItem](System.Collections.Generic.IEnumerable1[RecipeCategoryItem])’ method,and this method cannot be translated into a store expression.

我正在研究的部分是这一行.

RecipeCategories = r.RecipeCategories.Select(i => new RecipeCategoryItem { Id = i.ID,CategoryName = i.categoryName }).ToList()

RecipeCategories是List< RecipeCategoryItem>属性.

我正在尝试做什么,如果是这样,怎么样？

谢谢.

var ri = (from r in recipeData.Recipes
            where r.ID == recipeId
            select new RecipeItem
            {
                Id = r.ID,}).First();
var rc = from c in recipeData.RecipeCategories
         where c.Recipes.Any(r => r.ID == recipeId)
         select new RecipeCategoryItem 
         {
            Id = c.ID,CategoryName = c.categoryName
         };
ri.RecipeCategories = ri.ToList();