DevForce Community Forum : OrderBy

OrderBy : Helpful ideas, thanks!

Thu, 20 May 2010 06:08:21 -700

Author: evanian
Subject: 1821
Posted: 20-May-2010 at 6:08am

Helpful ideas, thanks!

OrderBy : You can't order by a spanned...

Wed, 19 May 2010 17:06:57 -700

Author: IdeaBlade
Subject: 1821
Posted: 19-May-2010 at 5:06pm

You can't order by a spanned column because the EntityList returned by the query only contains the primary Entity type (AS400Client in your case). You're trying to sort a collection of AS400Client entities on a column that doesn't exist on the AS400Client entity.

The effect of the span is simply to load the AS400Workplace into the cache as a byproduct of your query for AS400Clients.

If you want an entity that combines the columns of AS400Clients and AS400Workplace, you might want to create a view in your database and then base a new entity type on that. However, that tends to become problematic if you need to change and save the retrieved entities.

You could probably write an IComparer that would sort AS400Clients by a column on the related AS400Workplace (assuming that's a 1-1 relationship). See the example "Reusable MultiProperty Sorter" (and specifically the file MultiPropertyComparer.cs) under the BindableList topic in the 200 Intermediate Learning Units for an example of a custom IComparer

OrderBy : Is it possible to OrderBy a spanned...

Tue, 18 May 2010 09:17:39 -700

Author: evanian
Subject: 1821
Posted: 18-May-2010 at 9:17am

Is it possible to OrderBy a spanned column in an RdbQuery? What I would like to do is this:

            // Query
            _query = new RdbQuery(typeof(AS400Client));

            // Where clause
            _query.AddClause(    AS400Client.FirstNameEntityColumn,
                                EntityQueryOp.EQ,
                                "David");

            // Add span to other table
            _query.AddSpan(EntityRelations.AS400Workplace_AS400Client);

            // Add orderby on column in *related* table
            EntityOrderBy orderBy = new EntityOrderBy(AS400Workplace.DescriptionEntityColumn, ListSortDirection.Descending);

            _query.ClearOrderBy();
            _query.AddOrderBy(orderBy);

            // Get the clients
            PersistenceManager pm = PersistenceManager.DefaultManager;
            _clients = pm.GetEntities(_query);

Of course, I get an error: "Cannot find column Description."   Is there any way of doing this?

(The reason why I'm not simply defining the query as being of the AS400Workplace type is that I want, potentially, to order by columns in either table, dynamically, depending on user input).