How to add to end of array C#?

Question

How do I add a new item from a TextBox and Button on a Windows Form at the end of an ArrayList which references a class?

private product[] value = new product[4];

value[1] = new product("One",5)
value[2] = new product("Two",3)
value[3] = new product("Three",8)

Workflow

• Enter new products details into textbox1, textbox2, textbox3

• When I click Add the new product gets added to the array:

  value[1] = new product("One",5)
value[2] = new product("Two",3)
value[3] = new product("Three",8)
value[4] = new product("Four",2)

What is the code for doing this?

Answer 1

Arrays are zero indexed, so an array initialized to a size of 4 could only be accessed up to index 3...

If you wanted the array to grow, then you'd have to either initialize the array at least as large as you wanted to be able to grow to, or else you'd have to create a new array with the new larger size and copy the old array over; not very efficient.

In this case, you'd do better to use a collection like a list, rather than an array, so that the size can dynamically increase.

Answer 2

Arrays are fixed size, which means you can't add more elements than the number allocated at creation time, if you need a auto sizing collection you could use List<T> or an ArrayList

Example:

// using collection initializers to add two products at creation time
List<Product> products = new List<Product>{new Product("One",5), new Product("Two",3) };

// then add more elements as needed
products.Add(new Product("Three",8));

EDIT:

Please stop UPVOTING ME for such an trivial answer!!! I don't want all this rep or votes from a simple answer, thanks ;) (community wiki now)

Answer 3

I think you need a List<product> collection, looking at your code. Then just call the Add() method on it

Answer 4

Use List as other people mentioned. If you are set on arrays, use

Array.Resize<Product>(ref product, your new size);

If you're only going to be adding a couple of products (over the lifetime of your array) just do something like

Array.Resize<Product>(ref product, product.Length + 1);

If you are going to be adding a lot of products, you might want to do something similar to what List does - like this:

Array.Resize<Product>(ref product, product.Length * 2);

Answer 5

You can't add items to an array, you would have to create a new array that is larger and copy the items to it. There is a method for that, which is somewhat misleadingly named Resize as it doesn't actually resize the array:

Array.Resize<product>(ref value, 5);

If you want to add items to a collection, you should use a List instead:

private List<product> value = new List<product>();
value.Add(new product("One",5));
value.Add(new product("Two",3));
value.Add(new product("Three",8));

value.Add(new product("Four",2));

Edit:
If you want to resize the array, you might want to increase the size instead of resizing it to a specific value:

int index = value.Length;
Array.Resize<product>(ref value, index + 1);
value[index] = ...

Answer 6

You should probably also take a look at Array versus List: When to use which?