How to add additional value to an array?

Question

I am currently creating a program where the user can use a printer as long as that particular user has enough funds.

The current issue I am having is that if the user chooses to have colour printing instead of black and white then the price for each piece of paper goes up.

How do I add value to an already existing array?

Here is my code...

printers[0] = new Printer("printer1", 0.10M);
            printers[1] = new Printer("printer2", 0.08M);
            printers[2] = new Printer("printer3", 0.05M);
            printers[3] = new Printer("printer4", 0.15);
            printers[4] = new Printer("printer5", 0.09M);

            foreach (Printer r in mPrinters)
            {
                if (printer != null)
                    printerCombo.Items.Add(r.getName());
            }

Arrays are of fixed size by design. If want a collection that you can add, remove, insert then look at the classes in System.Collection.Generic or System.Collection.ObjectModel — John Alexiou
– John Alexiou, Commented Jan 20, 2017 at 20:00

Dmitrii Bychenko · Accepted Answer · 2017-01-20 20:07:54Z

3

Technically, you can Resize the array:

 Array.Resize(ref printers, printers.Length + 1);

 printers[printers.Length - 1] = new Printer("printer6", 0.25M);

However, a much better approach is to change the collection type: array into List<T>:

 List<Printer> printers = new List<Printer>() {
   new Printer("printer1", 0.10M),
   new Printer("printer2", 0.08M),
   new Printer("printer3", 0.05M),
   new Printer("printer4", 0.15),
   new Printer("printer5", 0.09M), }; 

 ...

 printers.Add(new Printer("printer6", 0.25M));

answered Jan 20, 2017 at 20:07

Dmitrii Bychenko

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2 Comments

Fran Over a year ago

Resize creates new a copies all the contents of the old array into the new one. It doesn't resize the original array.

Dmitrii Bychenko Over a year ago

@Fran: you are quite right (that's why we pass the array with ref when we call Array.Resize). However, this underhood behaviour, IMHO, doesn't matter much: we get the array with its Length increased and we know that the arrays are not supposed to change their sizes (so we should not use Array.Resize frequently)

Roman · Accepted Answer · 2017-01-20 19:57:08Z

1

Arrays have fixed size - after you created array with size 10 you can't add one more element (to make size 11).

Use List<Printer>:

List<Printer> printers = new List<Printer>();
printers.Add(new Printer("printer2", 0.08M));
//add all items

Also you can access elements by index:

var element = printers[0];

Using List you can change its size, add and remove elements.

answered Jan 20, 2017 at 19:57

Roman

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Comments

Fran · Accepted Answer · 2017-01-20 19:55:55Z

0

Arrays are fixed length. You need to copy the values into a new array or use an List, List<>, or ArraryList.

edited Jan 20, 2017 at 19:55

answered Jan 20, 2017 at 19:54

Fran

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4 Comments

Ondrej Tucny Over a year ago

No, they are not immutable. They just have a fixed length. Two different things.

Fran Over a year ago

true. updating answer.

TaW Over a year ago

ArrayList is pretty much outdated and we shouldn't advise using it. List<T> is the way to go.

Fran Over a year ago

Yes. I prefer stingy typed collections, but it's still part of the framework

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