Add Items to Array In C#

Question

I have a shopping cart that I iterate through in a foreach loop. Each Item in the cart needs to be added to an orderItemList array.

orderItemList = 
[{
orderItemId = 1,
quantity = 2
},{
orderItemId = 2, 
quantity =1 
}]

So I was trying to use

foreach(var items in shoppingCart)
{
var newOrderItems = new[] 
{  new orderItem { orderItemId = item.Id , quantity = item.quantity }
};

It is only adding the last item in the cart. It loops through and creates each one but only the last one is added. What am i missing?

newOrderItems only returns the one item even though it loops.

That's what its looking like but what i need to do is add to the array a new item. — Leonardo Wildt
– Leonardo Wildt, Commented Mar 24, 2017 at 22:33
arrays are fixed sized, you can't add to or remove an item from an array. — Selman Genç
– Selman Genç, Commented Mar 24, 2017 at 22:42

Ray Fischer · Accepted Answer · 2017-03-24 22:36:25Z

2

Each time in the loop you're creating a new array (hence the "new[]") with one item in it. An array's size cannot be changed so instead use a List<> object:

newOrderItems = new List<orderItem>();
foreach(var items in shoppingCart)
{
  newOrderItems.Add(new orderItem { orderItemId = item.Id , quantity =   item.quantity});
};

A List<> can be treated like an array for almost all purposes. If you NEED an array than you can easily convert it ...

var newOrderItemsArray = newOrderItems.ToArray();

answered Mar 24, 2017 at 22:36

Ray Fischer

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2 Comments

user5125586 Over a year ago

I can't see why this is the accepted answer as it does not answer the question. The question is about adding items to array not a list and also not converting a list into an array

Ray Fischer Over a year ago

He's creating a new array each time through the loop, not adding an item to an existing array. In fact you can't add to an array so I suggested using a List<> instead

DavidG · Accepted Answer · 2017-03-24 22:36:59Z

Rather than using an array, consider using one of the generic collection classes provided by the framework instead. These are designed to be added to and removed from (among many other things. For example:

var orderItems = new List<orderItem>();

foreach(var items in shoppingCart)
{
    orderItems.Add(new orderItem 
    {
        orderItemId = item.Id, 
        quantity = item.quantity 
    });
};

You could even do this with Linq and eliminate the foreach:

var orderItems = shoppingCart
    .Select(s => new orderItem
    {
        orderItemId = item.Id, 
        quantity = item.quantity 
    })
    .ToList();

littlerufe · Accepted Answer · 2017-03-24 22:51:37Z

1

Just declare your array outside the loop...here's an example using arrays:

OrderItem[] newOrderItems = new OrderItem[shoppingCart.Length];

for (int i = 0; i < shoppingCart.Length; i++)
{
    var item = shoppingCart[i];
    newOrderItems[i] = new OrderItem {orderItemId = item.Id, quantity = item.quantity};
}

There are other examples using List objects, but I think this is the coolest one-line way to convert all your shopping cart items into a List of OrderItem objects:

List<OrderItem> newOrderItems = shoppingCart.Select(item =>
    new OrderItem {orderItemId = item.Id, quantity = item.quantity}).ToList();

edited Mar 24, 2017 at 22:51

answered Mar 24, 2017 at 22:35

littlerufe

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2 Comments

CrociDB Over a year ago

You're creating a list, not an array.

DavidG Over a year ago

I'm always rather uncomfortable calling Linq statements "one-line" when they are really just a long chain of commands.

IngoB · Accepted Answer · 2017-03-24 22:42:32Z

0

You need to declare var newOrderItems = new List<orderItem>(); outside your foreach loop and then use

newOrderItems.Add(new orderItem {...});

If you declare it inside, it will be created again and again.

edited Mar 24, 2017 at 22:42

answered Mar 24, 2017 at 22:36

IngoB

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1 Comment

Ray Fischer Over a year ago

Arrays do not have an Add method. Your answer will not work

score 0 · Accepted Answer · 2017-03-24 23:29:42Z

0

Try:

for(var item in shoppingCart){
    var newOrderItems = new[] {  new orderItem { orderItemId = item.Id , quantity = item.quantity }};
    orderItemList = orderItemList.Concat(newOrderItems).ToArray();
}

Didn't get to test it but it should work.

edited Mar 24, 2017 at 23:29

answered Mar 24, 2017 at 22:57

user5125586

2 Comments

user5125586 Over a year ago

Why the downvote? You just had to point that out. Fixed that though.

littlerufe Over a year ago

because it doesn't compile. improper for syntax, item is not defined (it is now, though), order is not defined, etc...

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