Hello! I write a simple OLAP viewer for my web-site. Here are the classes (abstract example):

Employee
{
       ID;
       Name;
       Roles[]; //What Employee can do
}
Order
{
    Price;
    Employee Manager;
    Employee Executive; //Maybe wrong english. The person which perform order         
}

Employee can be Manager and Executive in the order at the same time. This means that Employee role is not fixed. I have to group orders by employees and finally get IGrouping with Employee key.

So .GroupBy(el=>new {el.Manager,el.Executive}) is not allowed.

I considered some tricks with IEqualityComparable, but found no solution.

If somrbody will help I'll be vary glad, thank you.