Question

Would like to both filter and convert a List. Is this the proper syntax? Filter on type and property.

FieldDefEnum1 : FieldDef 

List<FileDef> fieldDefs

public List<FieldDefEnum1> FieldDefsEnum1
{
    get
    {
        return FieldDefs.OfType<FieldDefEnum1>().ToList().Where(fd => fd.SysCus == enumSysCus.Cus).ToList();
    }
}

Answer 1

This will work fine but you have redundant .ToList() in the middle that will break deferred execution. try this:

FieldDefs.OfType<FieldDefEnum1>().Where(fd => fd.SysCus == enumSysCus.Cus).ToList();