Question

我根据一个教程创建了所有实体，并且似乎可以正常工作，至少创建了我的数据库表，但是我无法弄清楚如何使用以下设置插入任何新数据：

我的模型课：

public class Coffee 
{
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int CoffeeId { get; set; }

        [MaxLength(100)]
        [Required]
        public string Name { get; set; }

        [MaxLength(100)]
        [Required]
        public string ImagePath { get; set; }

        [MaxLength(100)]
        [Required]
        public string Price { get; set; }

        [MaxLength(400)]
        [Required]
        public string Description { get; set; }

        public virtual ICollection<IngredientCoffees> Ingredients { get; set; }
}

public class Ingredient 
{
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int IngredientId { get; set; }

        [MaxLength(100)]
        [Required]
        [StringLength(100, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 3)]
        public string Name { get; set; }

        [Required]
        public int Amount { get; set; }

        [Required]
        [StringLength(10, ErrorMessage = "The {0} must be at least {2} characters long.", MinimumLength = 1)]
        public string Unit { get; set; }

        public virtual ICollection<IngredientCoffees> Coffees { get; set; }
}

public class IngredientCoffees 
{
        public int Coffee_Id { get; set; }
        public int Ingredient_Id { get; set; }

        public virtual Coffee Coffee { get; set; }
        public virtual Ingredient Ingredient { get; set; }

        public int amount { get; set; }
}

在我的OnModelCreating类的DbContext方法中，我有这个：

builder.Entity<IngredientCoffees>()
                .HasKey(ic => new { ic.Coffee_Id, ic.Ingredient_Id });

builder.Entity<IngredientCoffees>()
                .HasRequired(ic => ic.Coffee)
                .WithMany(ic => ic.Ingredients)
                .HasForeignKey(ic => ic.Coffee_Id);

builder.Entity<IngredientCoffees>()
                .HasRequired(ic => ic.Ingredient)
                .WithMany(ic => ic.Coffees)
                .HasForeignKey(ic => ic.Ingredient_Id);

所有这些都将导致以下数据库结构：

my tables

如何在数据库中插入具有现有成分的新Coffee，使它们加入我的IngredientCoffees表中，我还想在其中将“金额”列设置为它们？ >

Answer 1

您可以使用数组或列表

if (context.Coffee .Any())
        {
            return;   // DB has been seeded
        }
 var coffees = new Coffee []
        {
            new Coffee { Name = "Coffee name",   ImagePath = "/[your path]",
                Price = "[price]", Description ="description" },
             new Coffee {......................}

         }

       foreach (Coffee coffee in coffees)
        {
            context.Coffee.Add(coffee);
        }
        context.SaveChanges();

您可以在同一文件中对成分进行相同操作

var ingredients= new Ingredient []
        {
            new Ingredient { Name = "Ingredient name",  
                 Amount = [your amount], Unit = "[ your unit ]"  },
             new Ingredient {......................}

         }

       foreach (Ingredient ingredient in ingredients)
        {
            context.Ingredient.Add(ingredient);
        }
        context.SaveChanges();

Answer 2

我已经找到了解决我所遇到问题的方法！似乎EF在您想要拥有自定义列（在我的情况下为amount）中的情况下对待很多很多关系，因此您必须做更多的手工工作，至少这是我读到的。这是我的方法：

//create a new coffee
var americano = new Coffee 
            {
                Name = "Americano",
                ImagePath = "https://imgurl.jpg",
                Price ="5",
                Description = "Americano is a type of coffee drink prepared by.."
            };

//select existing ingredient from the db
            var coffee_powder = context.Ingredients.Where(i => i.Name == "coffee powder")
                            .SingleOrDefault();

//if found, create a new IngredientCoffee
            if (coffee_powder != null) {
                var ingredientCoffees = new IngredientCoffees { Coffee = americano, Ingredient = coffee_powder, amount = 8 };

//add it, with this your new coffee will be created automatically too
                context.IngredientCoffees.Add(ingredientCoffees);


                context.SaveChanges();

            }

它将创建您的新行以及关联表中的正确ID。

如何在带有自定义多对多关联的Entity Framework中插入？

2 个答案: