How to query Dynamic properties in NHibernate?

I have this problem. I have a class like this:

public class WfStep
{
    private readonly IDictionary properties = new Hashtable();

    public virtual Guid Id { get; private set; }
    public virtual string Name { get; set; }
    public virtual dynamic Properties { get { return new HashtableDynamicObject(properties); } }

and its mapping file like this:

<class name="ConsoleApplication4.WfStep" table="WFSteps">

<id name="Id">
  <generator class="guid"/>
</id>
<property name="Name" />

<map name="Properties" table="WFSteps_Properties" access="field.lowercase">
  <key column="StepId" />
  <index column="PropertyName" type="System.String"/>
  <composite-element class="ConsoleApplication4.ValueItem, ConsoleApplication4">
    <property name="Value" type="System.String"/>
    <property name="ValueType" type="System.String"/>
  </composite-element>
</map>   

This example is ported from: Ayende Support dynamic fields with NHibernate and .NET 4.0

Then I save an object to the db like this: ie.

var step = new WfStep { Name = "John" };
var prop开发者_JS百科erty = new ValueItem() { Value = DateTime.Now, ValueType = "System.DateTime" };
step.Properties["DateProperty"] = property ;

Session.Save(step);

Now I want to return all the WFSteps that have DateProperty set to year 2010 ie.:

var Session.Query<WfStep>().Where(x=>x.Properties.DateProperty.Year == 2010);

It throws an error:

An expression tree may not contain a dynamic operation

How can I query this type of class that has Dynamic properties.?

You can index collections mapped as a map or as list. Try the following hql

from WfStep s
where s.Properties["DateProperty"] = "2010"