创建3列的键，包括与另一个表的关系（代码优先）

Question

i have a problem creating my database structure. For example i have those 3 classes

public class Product
{
    [Key, Column(Order = 1)]
    [Required]
    public string ItemNo { get; set; }

    [Key, Column(Order = 2)]
    [Required]
    public string VariantCode { get; set; }

    public virtual List<ProductAttribute> Attributes { get; set; }

    public Product()
    {
        Attributes = new List<ProductAttribute>();
    }
}

public class ProductAttribute
{
    [Key]
    [Required]
    public string FieldName { get; set; }

    public string FieldValue { get; set; }

    public virtual Product Item { get; set; }

}

public class DbContext : DbContext
{
    public DbSet<Product> Products { get; set; }
    public DbSet<ProductAttribute> Attributes { get; set; }
}

The primary key for the Product table is ItemNo + VariantCode and will be created correctly. The second table ProductAttribute should have a key of ItemNo + VariantCode + FieldName but with the code above EF6 creates a primary key FieldName and a foreign key of ItemNo + VariantCode. I have tried several things including setting the [Key] attribute to the Item property in the ProductAttribute class but this doesn't work. Any ideas how to do this?

Answer 1

Try following:

public class ProductAttribute
{
    [Key]
    [Required]
    public string FieldName { get; set; }

    public string FieldValue { get; set; }

    [Key]
    [ForeignKey("Item"), Column(Order = 1)]
    public string ItemNo { get; set; }

    [Key]
    [ForeignKey("Item"), Column(Order = 2)]
    public string VariantCode { get; set; }

    public virtual Product Item { get; set; }
}