NHibernate按代码映射和IUsertype无法正常工作

Question

我试图通过代码使用NHibernate(v3.3)映射来获得自定义类型.我在这里尝试了这个例子,但没有运气.我想要实现的自定义类型是一个修剪来自数据库的字符串的类型.

我收到以下异常:

PropertyAccessException:无效的转换(检查映射是否存在属性类型不匹配).{"无法将'System.String'类型的对象强制转换为'ConsoleApplication1.TrimmedString'."}

这是我的全部尝试(要点).

public class TrimmedString : IUserType
{
    public object NullSafeGet(IDataReader rs, string[] names, object owner)
    {
        //treat for the posibility of null values
        string resultString = (string) NHibernateUtil.String.NullSafeGet(rs, names[0]);
        if (resultString != null)
            return resultString.Trim();
        return null;
    }

    public void NullSafeSet(IDbCommand cmd, object value, int index)
    {
        if (value == null)
        {
            NHibernateUtil.String.NullSafeSet(cmd, null, index);
            return;
        }

        value = ((string) value).Trim();

        NHibernateUtil.String.NullSafeSet(cmd, value, index);
    }

    public object DeepCopy(object value)
    {
        if (value == null) return null;
        return string.Copy((String) value);
    }

    public object Replace(object original, object target, object owner)
    {
        return original;
    }

    public object Assemble(object cached, object owner)
    {
        return DeepCopy(cached);
    }
    public object Disassemble(object value)
    {
        return DeepCopy(value);
    }

    public SqlType[] SqlTypes
    {
        get
        {
            SqlType[] types = new SqlType[1];
            types[0] = new SqlType(DbType.String);
            return types;
        }
    }

    public Type ReturnedType
    {
        get { return typeof (String); }
    }

    public bool IsMutable
    {
        get { return false; }
    }

    public new bool Equals(object x, object y)
    {
        if (ReferenceEquals(x, y)) return true;

        var xString = x as string;
        var yString = y as string;
        if (xString == null || yString == null) return false;

        return xString.Equals(yString);
    }

    public int GetHashCode(object x)
    {
        return x.GetHashCode();
    }
}

这是我的映射:

public class Person
{
    public virtual int Id { get; set; }
    public virtual TrimmedString FirstName { get; set; }
    public virtual string LastName { get; set; }
}

public class PersonMap : ClassMapping<Person>
{
    public PersonMap()
    {
        Table("Source");
        Id(i => i.Id);
        Property(i => i.FirstName, map => map.Type<TrimmedString>());
        Property(i => i.LastName);
    }
}

不确定我是否必须在NHibernate配置对象中做任何特殊操作,但我已将其包含在上面链接的Gist中.

Answer 1

在Person,它应该是......

public virtual string FirstName { get; set; }

......,不是TrimmedString. TrimmedString只是指导NHibernate如何让你的财产得到保湿和脱水的课程.它应用的属性应该是由ReturnedType- 指定的类型- 换句话说,String.NHibernate试图FirstName用一个string值设置属性(因为这就是TrimmedString它应该做的事情),但它不能因为FirstName只允许TrimmedStrings,因此"Invalid Cast"错误.