Question

我正在考虑如何在一对多关系上编写正确的LINQ查询或lambda表达式，同时在Entity Framework的“多”方面对实体进行适当的过滤。

所以两个实体是：

配方
ID
名称输入[small | big]

成分
ID
recipeId
命名
输入[常规|异国情调]

那么如何编写一个LINQ查询来选择小而具有异国情调成分的食谱？

它可能会像：

var smallExoticRecipes = contex.Recipes.Include("Ingredients").Where(recipe => recipe.Type == "small" && ????);

我需要写什么而不是“????”？或者我应该尝试使用LINQ查询而不是lambda表达式？

更新
在“选择”条款中，我想只选择食谱及其特殊成分，而不是常规成分，尽管它们也可能有吗？

所以：

我应该这样，对吗？

.Select(recipe => new { recipeName = recipe.Name, recipeIgredients = recipe.Ingredients.Where(ing => ing.Type == "exotic" });

Answer 1

var smallExoticRecipes = contex.Recipes.Include("Ingredients").Where(recipe => recipe.Type == "small" && recipe.Ingredients.Any(i => i.type == "exotic"));

当然，为了清晰起见，您可能需要将其分开：

Func<Recipe, bool> hasExoticIngredients = r => r.Ingredients.Any(i => i.type == "exotic");
var smallExoticRecipes = context.Recipes.Include("Ingredients").Where(recipe => recipe.Type == "small" && hasExoticIngredients(recipe));

另一种选择是：

Func<Recipe, bool> hasExoticIngredients = r => r.Ingredients.Any(i => i.type == "exotic");
Func<Recipe, bool> isSmallAndExotic = r => recipe => recipe.Type == "small" && hasExoticIngredients(recipe)
var smallExoticRecipes = context.Recipes.Include("Ingredients").Where(isSmallAndExotic);

Answer 2

var smallExoticRecipes = contex.Recipes.Include("Ingredients").Where(recipe => recipe.Type == "small" && ingredients.Any( ingredient => ingredient.recipeid == recipe.id && ingredient == "exotic"));

如何在与filter的一对多关系上编写LINQ查询或Lambda表达式

2 个答案: