I'm getting an error while trying to load an record through the constructor.

The constructor is: 

```
public Document(Expression<Func<Document,bool>> expression);

```

and i try to load a single item in like this

```
var x = new Document(f=>f.publicationnumber=="xxx");

```

publicationnumber isn't a key but tried making an it an unique key and still no go..

Am i totally wrong regarding the use of the constructor? and can someone please tell me how to use that constructor?

The error i'm getting is:  

Test method TestProject1.UnitTest1.ParseFileNameTwoProductSingleLanguage threw exception: System.NullReferenceException: 

with the following stacktrace: 

> 
> SubSonic.Query.SqlQuery.Where`[T]`(Expression`1` expression)  
> 
>  Load`[T]`(T item, Expression`1`expression)  
> 
>  db.Document..ctor(Expression``1` expression) in C:\@Projects\DocumentsSearchAndAdmin\DocumentsSearchAndAdmin\Generated\ActiveRecord.cs: line 5613  
> 
>  rest removed for simplicity
> 
> 
> 

Regards  

Dennis