For some reason I extend the Entity with help of a partial class. The property is this case is a boolean called "Visible".

Is something like the following code possible:

            PredicateExpression filter = null;
            filter = new PredicateExpression(new FieldInfo("Visible").Value == true);
            mDataStore.CandidatesEnhanced.DefaultView.Filter = filter;

Yes though not that way, you need to use a DelegatePredicate

http://www.llblgen.com/Documentation/5.1/LLBLGen%20Pro%20RTF/Using%20the%20generated%20code/Filtering%20and%20Sorting/gencode_filteringpredicateclasses.htm#delegatepredicate-and-delegatepredicateof-t

Thanks