Is it possible to use Expressions with EntityCollections. I want to do something like this, but can't get the syntax right.

    EntityCollection orderDetails = new EntityCollection();
    MyExpression myExpression= new MyExpression (DocumentFields.CreatedDate);
    orderDetails**.Fields**[DocumentFields.CreatedDate.Name.ToString()].SetExpression(myExpression);

Or is the only way to do it like this:

        ResultsetFields fields = new ResultsetFields(5);
        fields.DefineField(DocumentFields.Queue, 0);
        MyExpression myExpression = new MyExpression (DocumentFields.CreatedDate);
        fields[0].SetExpression(myExpression);

Would you please explain what exactly that you want to do? I mean what is the SQL query that you want to execute? How does your expression look like?

Which version of LLBLGen Pro are you using?

The expression I am writing is to execute XQuery against a SQL Server 2005 XML column.

So the SQL I am trying to write is something like:

select xmlcolumn.query('/root/mynode') from myTable where someOtherColumn <10

The expression is working fine against a single entity, but I am trying to SETEXPRESSION against the column for an EntityCollection.

I am using v2.

I think you should use a Dynamic List and then you might project the resultset back to an entityCollection.

How can I cast a DataTable back into an EntityCollection?

Is there a reason why this is so, or has the SetExpression method just not been implemented on an EntityCollection yet?

How can I cast a DataTable back into an EntityCollection?

Please consult the v.2.0 manual: "Using the generated code -> Adapter/SelfServicing -> Fetching DataReaders and projections"

We will get back to you on the 2nd question ASAP.

The fetched data in the select list using the XQuery, is that data forming an entity? I have the feeling it's not, (i.e it's a list, though not an entity as known in table/view form). Using an expression in an entitycollection can be done though. Please see the example in this article (where I modify the factory to add a new field, you can also use this to set an expression on a field). http://weblogs.asp.net/fbouma/archive/2006/06/09/LLBLGen-Pro-v2.0-with-ASP.NET-2.0.aspx