NHibernate搜索条件

Question

I have class Definition with property string Data

public class Definition
{
  string Type  {get; set; }
  string Data  { get; set; }
}

Then Data contains some XML that saved as string

<Definition>
    <Property>
     <Key>DefinitionId</Key>
     <Value>5</Value>
    </Property>   
</Definition>

I need to get all Definitons where DefinitionId is 5.

What the best way to do it? To get all definitions and parsed them or i can do something with NHibernate?

Answer 1

You can query Xml types with NHibernate if your DB supports Xml querying. Assuming you're working with Sql Server 2005+ ...

Step 1 - Class Definition

Change your class Definition to:

public class Definition
{
  string Type  {get; set; }
  XDocument Data  { get; set; }
}

Your mapping should pick the XDocument type and create a the appropriate Xml column type for the Data column in the database.

Step 2 - Querying

A couple of different ways to query, but they boil down to the same thing. The code below shows the querying via the QueryOver api:

session.QueryOver<Definition>()
       .Where
        (
            Restrictions.Eq
            (
                Projections.SqlProjection
                (
                   "Data.value('(/Definition/Property/Value)[1]', 'int') as DefinitionId",
                   new string[] { "DefinitionId" },
                   new IType[] { NHibernateUtil.Int32 }
                ),
                5
            )
        )
       .List();

The above query uses standard Sql Server XQuery to query the Xml field. A little introduction on XQuery language: http://blog.sqlauthority.com/2012/04/27/sql-server-introduction-to-discovering-xml-data-type-methods-a-primer/