CODEWITHSUNDEEP
c#listsortedset
user3429270
user3429270

Reputation: 31

C# Adding objects to List

I have just started learning c# and am having a slight problem with a program I'm creating.

I'm creating a program which will create a Number of lotto tickets each with an ID and six randomly generated numbers.

Here is my code for creating the tickets and adding them to a List.

Random random = new Random();// Random number generator
for (int i = 0; i < 1000; i++)
{
    do
    {
    int randomNumber = random.Next(1, 42);// Create randoms numbers between 1 and 42
    ticketNumbers.Add(randomNumber);// Add the random numbers to the ticketNumbers SortedSet                  
    }
    while (ticketNumbers.Count< 6);// Stop Adding once the six numbers is reached

    CTicket firstTicket;
    firstTicket = new CTicket(i, ticketNumbers);// Create ticket object pass i's current value as the ticket id and pass the ticketNumbers sorted set as the ticket numbers
    ticketList.Add(firstTicket);// Add the firstTicket object to the ticketList
    ticketNumbers.Clear();// clear the ticketNumbers list to start again for the next ticket
}

CTicket.Printlist(ticketList);

Here is my function to print the list:

public static void Printlist(List<CTicket> ticketList)
{
    foreach (CTicket mytick in ticketList)
    {
        Console.WriteLine("Ticket ID = {0} ", mytick.m_ticketID);

        foreach (int val in mytick.m_ticketNumbers)
        {
            Console.WriteLine(val);
        }                            
    }
}

My problem is when I create a ticket object and add it to the list the print function will only display the id and not the numbers. I have traced the issue to the following:

ticketNumbers.Clear();

It appears that the list is also being cleared for all previous ticketNumbers which are used in creating the objects

Could someone please explain to me why this is happening?

Upvotes: 0

Views: 321

Answers (2)

sean
sean

Reputation: 811

When you create your CTicket instance,

firstTicket = new CTicket(i, ticketNumbers);

the ticketNumbers is a reference to a SortedSet instance which is being passed to the CTicket class. All your CTicket instances contain a copy of a reference to this same SortedSet instance. When you clear that, all CTickets will reference the same empty set.

The solution is to create a new ticketNumbers set for each CTicket, then each CTicket will contain a reference to a different set.

Random random = new Random();// Random number generator
for (int i = 0; i < 1000; i++)
{
    SortedSet<int> ticketNumbers = new SortedSet<int>();
    do
    {
    int randomNumber = random.Next(1, 42);// Create randoms numbers between 1 and 42
    ticketNumbers.Add(randomNumber);// Add the random numbers to the ticketNumbers SortedSet                  
    }
    while (ticketNumbers.Count< 6);// Stop Adding once the six numbers is reached

    CTicket firstTicket;

    firstTicket = new CTicket(i, ticketNumbers);// Create ticket object pass i's current value as the ticket id and pass the ticketNumbers sorted set as the ticket numbers
    ticketList.Add(firstTicket);// Add the firstTicket object to the ticketList
    ticketNumbers.Clear();// clear the ticketNumbers list to start again for the next ticket
}

CTicket.Printlist(ticketList);

See here for more information on passing reference type parameters in C#.

Upvotes: 6

Viru
Viru

Reputation: 2246

@sean explained you have to re intialize list variable instead of clear

ticketNumbers = new List<int>();

Upvotes: 0

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