删除级联不起作用

Question

我的数据库中有两张表，一张用于食谱，一张用于配料。当一个特定的食谱被删除时，我希望它的所有成分也都消失。我已经声明了与级联属性集的一对多关系，但是当我删除一些食谱时，它不会删除相关成分。

这是我的表格：

    public class Recipe_Model
    {

        [PrimaryKey AutoIncrement]
        public int RecipeID { get; set; }
        public string RecipeName { get; set; }
        public double RecipeCost { get; set; }
        public double ServingsNo { get; set; }
        public double CostPercent { get; set; }
        public double SellingPrice { get; set; }
        public double CostPerServing { get; set; }

        [OneToMany(CascadeOperations = CascadeOperation.All)]      // One to many relationship with Ingredients
        public ObservableCollection<Ingredients_Model> Ingredients { get; set; }
    }

    public class Ingredients_Model
    {
        [PrimaryKey AutoIncrement]
        public int IngredientID { get; set; }

        [ForeignKey(typeof(Recipe_Model))]
        public int RecipeID { get; set; }

        public string IngredientName { get; set; }
        public string UsedUnit { get; set; }
        public string PurchasedUnit { get; set; }
        public double QuantityUsed { get; set; }
        public double QuantityPurchased { get; set; }
        public double PurchasePrice { get; set; }
        public double IngredientCost { get; set; }
    }

这是我的删除操作：

    public void DeleteRecipe()
    {
        using (SQLiteConnection database = DependencyService.Get<ISQLite>().GetConnection())
        {
            var recipe = database.Get<Recipe_Model>(RecipeID);
            database.Delete(recipe, true);
        }
    }

我做错了什么？

Answer 1

级联操作仅适用于内存中的对象。在您的特定场景中，您通过 Get 方法从数据库中获取单个对象，级联操作将删除所有内存中的关系，目前没有任何关系，因为 Ingredients 属性是 null.

如果您还没有内存中的对象，加载它们只是为了获取标识符以删除它们是没有意义的，这正是级联删除所做的：

// This would work as it loads children to memory, but it's inefficient
var recipe = database.GetWithChildren<Recipe_Model>(RecipeID);
database.Delete(recipe, true);

相反，我建议您手动删除它们：

database.Execute("DELETE FROM [Ingredients_Model] WHERE [RecipeID] == ?", recipe.Id);
database.Delete(recipe);

删除级联不起作用

Delete Cascade not working

xamarin.forms

cascading-deletes

sqlite-net-extensions