I'm trying to build a fully dynamic DataTable with Primefaces 5.0.

I've got a Config-Object for eachs column and I want the DT to sort by one of them from the beginning.

Here's my DT:

```
<p:dataTable id="ticketTable"
                 widgetVar="ticketTable"
                 value="#{ticketBean.ticketDataModell}"
                 var="ticket"
                 lazy="true"
                 paginator="true"
                 rows="20"
                 sortBy="#{dataPortletConfigBean.sortByKey}"
                 >

```

The sortByKey is a String. It's the name of the Variable I want to sort by.
So I want to replace something like `sortBy="key"` with `sortBy="#{bean.GiveMeAKey}"`.

But it doesn't work.
I get this: `could not resolve property: sortByKey of: [...]`

How can I get this to work?
Thanks