使用 Entity-Framework 的外键问题

Question

我正在使用 Entity Framework 并且有这两个类:

[Table("Client")]
public class Client
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public long ClientCode { get; set; }

public string Nombre { get; set; }
}

[Table("Product")]
public class Product
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.None)]
public string CodProd { get; set; }

[StringLength(80)]
public string NameProd { get; set; 

public Client Client { get; set; };
}

然后我像这样实例化一个新产品：

Product prod = new Product
            {
                CodProd = "Code",
                NameProd = "Name",
                Client = new Client { ClientCode = 12345678 }
            };

db.Products.Add(prod);
db.SaveChanges();

当我添加和保存这个对象时，并没有将它记录在数据库中，但是如果我在客户端属性中使用一个 NULL 值来实例化该产品，确实会出现，但具有该 NULL 值。我不知道为什么会这样...

Answer 1

假设您在 Client 和 Product 之间有一对多关系，您的代码应该如下所示：

[Table("Client")]
public class Client
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public long ClientCode { get; set; }

    public string Nombre { get; set; }

    public virtual ICollection<Product> Products { get; set; }
}

[Table("Product")]
public class Product
{
    [Key]
    [DatabaseGenerated(DatabaseGeneratedOption.None)]
    public string CodProd { get; set; }

    [StringLength(80)]
    public string NameProd
    {
        get; set;
    }

    [ForeignKey("Client")]
    public long ClientCode { get; set; } //foreign key property

    public virtual Client Client { get; set; } //navigation property
}

然后

Product prod = new Product
            {
                CodProd = "Code",
                NameProd = "Name",
                ClientCode = 12345678
            };

db.Products.Add(prod);

使用 Entity-Framework 的外键问题

A problem with the foreign key using Entity-Framework

c#

sql

entity

entity-framework

visual-studio