我有以下情形:在NHibernate中查询用户类型
假设我在此旧数据库中的“产品”表具有字符串类型的“类别”列。此列存储类别ID由某种ascii字符分隔。例如:“| 1 |” (对于类别1),“| 1 | 2 | 3 |” (对于类别1,2,3)等
而不是公开一个字符串属性,我想公开一个IEnumerable,以便我的产品类的用户不必担心解析这些值。
我创建一个SelectedCatories类型简直是一个IEnumerable,我的产品类看起来是这样的:
public class Product
{
public virtual Guid Id { get; set; }
public virtual string Name { get; set; }
public virtual bool Discontinued { get; set; }
public virtual SelectedCategories Categories { get; set; }
}
然后,我创建了一个SelectedCategoriesUserType类,像这样:
public class SeletedCategoriesUserType : IUserType
{
static readonly SqlType[] _sqlTypes = {NHibernateUtil.String.SqlType};
public bool Equals(object x, object y)
{
// Fix this to check for Categories...
if (ReferenceEquals(x, y)) return true;
if (x == null || y == null) return false;
return x.Equals(y);
}
public int GetHashCode(object x)
{
return x.GetHashCode();
}
public object NullSafeGet(IDataReader rs, string[] names, object owner)
{
object obj = NHibernateUtil.String.NullSafeGet(rs, names[0]);
if (obj == null) return null;
string[] stringCategories = obj.ToString().Split(new[] {'|'}, StringSplitOptions.RemoveEmptyEntries);
var categories = new Categories();
return
new SelectedCategories(
stringCategories.Select(
stringCategory => categories.Single(cat => cat.Id == int.Parse(stringCategory)))
.ToList());
}
public void NullSafeSet(IDbCommand cmd, object value, int index)
{
if (value == null)
{
((IDataParameter) cmd.Parameters[index]).Value = DBNull.Value;
}
else
{
var theCategories = (SelectedCategories) value;
var builder = new StringBuilder();
builder.Append("|");
theCategories.ForEach(i => builder.AppendFormat("{0}|", i.Id.ToString()));
((IDataParameter) cmd.Parameters[index]).Value = builder.ToString();
}
}
public object DeepCopy(object value)
{
return value;
}
public object Replace(object original, object target, object owner)
{
throw new NotImplementedException();
}
public object Assemble(object cached, object owner)
{
throw new NotImplementedException();
}
public object Disassemble(object value)
{
throw new NotImplementedException();
}
public SqlType[] SqlTypes
{
get { return _sqlTypes; }
}
public Type ReturnedType
{
get { return typeof (SelectedCategories); }
}
public bool IsMutable
{
get { return false; }
}
}
我当时想建立一个查询,让我回到属于特定类别(比如2类)的任何产品,匹配“| 2 |”和“| 1 | 2 | 3 |”。
现在,我天真的实现,勉强让我测试通过如下:
public IEnumerable<Product> GetByCategory(Category category)
{
using (ISession session = NHibernateHelper.OpenSession())
{
return session
.CreateSQLQuery("select * from product where categories LIKE :category")
.AddEntity(typeof(Product))
.SetString("category", string.Format("%|{0}|%", category.Id))
.List()
.Cast<Product>();
}
}
我的问题是:什么是要正确的查询的正确方法?
只是为了阐明:该查询不适合您,或者您想知道一种“更干净”的方式来编写您的查询吗?而且它是强制性的,你的类别ID由|分隔或者他们也可以用逗号(,)分隔? – Max 2010-11-15 21:03:00