Entity Framework一对一共享键关系下Nutrition未随父实体自动删除问题

方案1：调整关系主体（推荐，符合一对一共享表设计） #

让Nutrition作为依赖实体，复用Recipe或Ingredient的主键作为自身主键，确保每个Nutrition仅属于一个实体，同时配置级联删除：

修改实体类 #

public class Recipe
{
    public int RecipeId { get; set; }
    public string Name { get; set; }
    public string Instructions { get; set; }

    public Nutrition Nutrition { get; set; }
}

public class Ingredient
{
    public int IngredientId { get; set; }
    public string Name { get; set; }

    public Nutrition Nutrition { get; set; }
}

public class Nutrition
{
    [Key]
    public int NutritionId { get; set; }

    public int Calories { get; set; }
    public int Protein { get; set; }
    public int Carbohydrates { get; set; }
    public int Fat { get; set; }

    // 每个Nutrition仅会有其中一个导航属性非空
    public Recipe Recipe { get; set; }
    public Ingredient Ingredient { get; set; }
}

修改DbContext配置 #

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    // Recipe与Nutrition一对一，Recipe为主体，级联删除Nutrition
    modelBuilder.Entity<Recipe>()
        .HasOne(r => r.Nutrition)
        .WithOne(n => n.Recipe)
        .HasForeignKey<Nutrition>(n => n.NutritionId)
        .OnDelete(DeleteBehavior.Cascade);

    // Ingredient与Nutrition一对一，Ingredient为主体，级联删除Nutrition
    modelBuilder.Entity<Ingredient>()
        .HasOne(i => i.Nutrition)
        .WithOne(n => n.Ingredient)
        .HasForeignKey<Nutrition>(n => n.NutritionId)
        .OnDelete(DeleteBehavior.Cascade);

    // 添加约束，确保Nutrition只能关联单一实体
    modelBuilder.Entity<Nutrition>()
        .HasCheckConstraint("CK_Nutrition_SingleAssociation", 
            "[RecipeId] IS NULL OR [IngredientId] IS NULL")
        .HasCheckConstraint("CK_Nutrition_HasAssociation", 
            "[RecipeId] IS NOT NULL OR [IngredientId] IS NOT NULL");
}

方案2：手动删除Nutrition（无需修改实体结构） #

如果不能调整现有实体设计，可在删除Recipe/Ingredient时手动删除关联的Nutrition：

var ingredient = context.Ingredients
                    .Include(i => i.Nutrition)
                    .SingleOrDefault(x => x.IngredientId == id);

if (ingredient != null)
{
    context.Ingredients.Remove(ingredient);
    if (ingredient.Nutrition != null)
    {
        context.Nutritions.Remove(ingredient.Nutrition);
    }
    context.SaveChanges();
}

方案3：数据库触发器（适合已上线的数据库） #

在数据库中创建触发器，当Recipe/Ingredient被删除时自动清理对应的Nutrition：

-- Ingredients表删除触发器
CREATE TRIGGER TR_Ingredients_CleanNutrition
ON Ingredients
AFTER DELETE
AS
BEGIN
    DELETE FROM Nutritions
    WHERE NutritionId IN (SELECT NutritionId FROM DELETED)
END

-- Recipes表删除触发器
CREATE TRIGGER TR_Recipes_CleanNutrition
ON Recipes
AFTER DELETE
AS
BEGIN
    DELETE FROM Nutritions
    WHERE NutritionId IN (SELECT NutritionId FROM DELETED)
END

内容的提问来源于stack exchange，提问作者Simon H.