Question

So I am abit stuck on a linq statement below,

        public void ReturnHire(string carregistration, string hirefromdate, string hiretodate)
        {
            var result = customermembers.Where(c => c.CustomerCarType.Where(n => String.Equals(n.CarRegistration, carregistration)).FirstOrDefault(); // this line
            if (result != null)
            {
                customermembers.ForEach(c => c.CustomerHireDate.RemoveAll(cs => cs.HireFromDate == hirefromdate && cs.HireToDate == hiretodate));
                customermembers.ForEach(c => c.CustomerCarType.RemoveAll(cs => cs.CarRegistration == carregistration));
            }
        }

My xml looks like this:

<ArrayOfCustomer>
    <Customer>
        <CustomerID>1</CustomerID>
        <FirstName>G</FirstName>
        <LastName>Graam</LastName>
        <Age>27</Age>
        <CustomerHireDate>
            <HireDate>
                <HireFromDate>15.07.2012</HireFromDate>
                <HireToDate>29.07.2012</HireToDate>
            </HireDate>
        </CustomerHireDate>
        <CustomerCarType>
            <CarType>
                <CarRegistration>IAWB-OOTO</CarRegistration>
            </CarType>
        </CustomerCarType>
    </Customer>
</ArrayOfCustomer>

On my client side the customer is to “return” the vehicle, for me this is basically just removing the hire to and from dates and removing the registration number from within the customer. But here is the catch I have to do this deletion with just the registration number so I was trying to do a where within a where claus but it says I cant implcitly convert CarType to bool.

My web service has these lists:

        List<Customer> customermembers = new List<Customer>();
        List<HireDate> hiredates = new List<HireDate>();
        List<CarType> cartypes = new List<CarType>();

I just thought customermembers where customer car type where rehistration number equals mystring would have been fine?

Answer 1

Since you don’t actually use result in your if block, you could do this:

    public void ReturnHire(string carregistration, string hirefromdate, string hiretodate) 
    { 
        if (customermembers.Any(c => c.CustomerCarType.Any(n => String.Equals(n.CarRegistration, carregistration)))
        { 
            customermembers.ForEach(c => c.CustomerHireDate.RemoveAll(cs => cs.HireFromDate == hirefromdate && cs.HireToDate == hiretodate)); 
            customermembers.ForEach(c => c.CustomerCarType.RemoveAll(cs => cs.CarRegistration == carregistration)); 
        } 
    } 

Any returns true if there is at least one element that satisfies the predicate.

This is not terribly efficient, however, since you’re iterating the list three times; you should iterate it just once. I would post an example, but I think there’s a bug in your code and I don’t want to repeat it. Consider separate customers with separate registrations with the same hirefromdate and hiretodate. Your code would remove the CustomerHireDate from the customer who did not yet return the car.

However, you may well have intended to use result in the if block, which should fix the bug:

    public void ReturnHire(string carregistration, string hirefromdate, string hiretodate) 
    { 
        var result = customermembers.Where(c => c.CustomerCarType.Any(n => String.Equals(n.CarRegistration, carregistration));
        foreach (var customermember in result)
        { 
            customermember.CustomerHireDate.RemoveAll(cs => cs.HireFromDate == hirefromdate && cs.HireToDate == hiretodate); 
            customermember.CustomerCarType.RemoveAll(cs => cs.CarRegistration == carregistration); 
        } 
    }

Remember that Where does not change the original collection, so you need to iterate over result in order to get the filtered set of objects.