Nhibernate尝试在保存时添加重复列

我正在尝试使用Fluent NHibernate。我已经设置了两个表产品和类别。Products有一个CategoryID字段和一个外键，将Products的CategoryID绑定到Categories表的PK (CategoryID)。

DTO:产品类别:

public class Product
{
    [HiddenInput(DisplayValue = false)]
    public virtual int ProductId { get; set; }
    public virtual string Name { get; set; }
    public virtual int CategoryId { get; set; }
    [DataType(DataType.MultilineText)]
    public virtual string Description { get; set; }
    public virtual decimal Price { get; set; }
    public virtual decimal SalePrice { get; set; }
    public virtual int StockAmt { get; set; }
    public virtual bool StockLevelWarning { get; set; }
    public virtual string Dimensions { get; set; }
    public virtual bool PriceIncludesTax { get; set; }
    public virtual string TaxClass { get; set; }
    public virtual decimal ProductWeight { get; set; }
    public virtual decimal CubicWeight { get; set; }
    public virtual string PackageDimensions { get; set; }
    public virtual bool IncludeLatestProduct { get; set; }
    public virtual Category Category { get; set; }
    public Product()
    {
        Name = String.Empty;
        Description = String.Empty;
        Price = 0m;
        SalePrice = 0m;
        StockAmt = 0;
        StockLevelWarning = true;
        Dimensions = String.Empty;
        PriceIncludesTax = false;
        TaxClass = String.Empty;
        ProductWeight = 0;
        CubicWeight = 0;
        PackageDimensions = String.Empty;
        IncludeLatestProduct = false;
    }
}

在我的ProductMap类中，我有一个根据Fluent文档指定的一切，包括最后一个属性设置为引用:

   public class ProductMap : ClassMap<Product>
{
    public ProductMap()
    {
        Table("Products");
        Id(x => x.ProductId);
        Map(x => x.Name);
        Map(x => x.CategoryId);
        Map(x => x.Description);
        Map(x => x.Price);
        Map(x => x.SalePrice);
        Map(x => x.StockAmt);
        Map(x => x.StockLevelWarning);
        Map(x => x.Dimensions);
        Map(x => x.PriceIncludesTax);
        Map(x => x.TaxClass);
        Map(x => x.ProductWeight);
        Map(x => x.CubicWeight);
        Map(x => x.PackageDimensions);
        Map(x => x.IncludeLatestProduct);
        References(x => x.Category);
    }
}

DTO: Category:

public class Category
{
    public virtual int CategoryId { get; set; }
    public virtual string Name { get; set; }
    public virtual string Description { get; set; }
    public virtual IList<Product> Products { get; set; }
    public Category()
    {
        Name = string.Empty;
        Description = string.Empty;
    }
}

public class CategoryMap : ClassMap<Category>
{
    public CategoryMap()
    {
        Table("Categories");
        Id(x => x.CategoryId);
        Map(x => x.Name);
        Map(x => x.Description).Column("CategoryDescription");
        HasMany(x => x.Products);
    }
}

然而，当我尝试对Product实体进行保存时，我得到一个MySQL错误，返回我试图添加两次CategoryID。当查看堆栈跟踪时，它指定了NHibernate试图保存的列。实际上，它不仅按照我在ProductMap类中指定的顺序列出了CategoryID，而且再次将其列为插入语句中的最后一列。

  Error:
  "could not insert: [DTOS.Product][SQL: INSERT INTO Products (Name, CategoryId, Description, Price, SalePrice, StockAmt, StockLevelWarning, Dimensions, PriceIncludesTax, TaxClass, ProductWeight, CubicWeight, PackageDimensions, IncludeLatestProduct, Categoryid) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)]"}

我正在遵循Fluent文档使用的作者到Book示例。

就好像它将Product类上的属性(类型Category)等同于Category表的主键。但正如我提到的，我使用的是来自Fluent示例代码的相同示例。

public class ProductMap : ClassMap<Product>
{
    public ProductMap()
    {
        Table("Products");
        Id(x => x.ProductId);
        References(x => x.Category).Column("CategoryId");
    }
}
public class CategoryMap : ClassMap<Category>
{
    public CategoryMap()
    {
        Table("Categories");
        Id(x => x.CategoryId);
        HasMany(x => x.Products).KeyColumn("ProductId");
    }
}

Map(x => x.CategoryId);
References(x => x.Category);