This works: building the predicate in a separate function, passing the "customer" value from the higher-level lambda as a parameter.
publicvoid FindInterestingOrderItems(bool onlyIncludePendingItemsOverLimit)
{
var customers = GetCustomersWithOrders();
var interestingOrderItems = customers
.SelectMany(customer => customer.PendingOrders
.SelectMany(order => order.Items
.Where(GetFilter(customer, onlyIncludePendingItemsOverLimit))
.Union(customer.FailedOrderItems)))
.OrderByDescending(orderItem => orderItem.Amount);
}
private Func<OrderItem, bool> GetFilter(Customer customer, bool onlyIncludePendingItemsOverLimit)
{
if (onlyIncludePendingItemsOverLimit)
{
return orderItem => orderItem.Amount > customer.MaxOrderItemAmount;
}
else
{
return orderItem => true;
}
}