Adding c# Array to a List of Array's

Question

Fairly new to c# and a bit confused...

I have a class that retrieves 2 values and places them inside an array, I then wish to add the array to a list.

The array acts as an item for purchase and the list will act as the basket.

public void Add(int Id , int Quantity )
{
    int[] buying = new int[] { Id, Quantity };
    //AddTo(buying);

    List<int[]> arrayList = new List<int[]>();
    arrayList.Add(buying);
}

I'm just stuck on how to add to the list without creating a new instance of a list and there fore loosing any items already added?

Thanks for any help :)

Why do you have a list of arrays instead of a list of lists? — George Stocker
– George Stocker, Commented Mar 1, 2014 at 16:38
You need to define the array either as a class field and add to that, or instant irate it in the caller and pass it in. — Ant P
– Ant P, Commented Mar 1, 2014 at 16:39
It seems like the item for purchase should be an object instead of a naked array, especially if the elements in that array have specific meaning depending on their placement. — George Stocker
– George Stocker, Commented Mar 1, 2014 at 16:39
The initial array is ok, IMO ...it is finite with 2 elements with specific indication of purpose. At least in starting out. A new developer to C# will have to progressively step through development and learning the OPP-prefered methodologies. — IAbstract
– IAbstract, Commented Mar 1, 2014 at 16:40
just define the List<int[]> as part of the class instance (rather than as part of the method) and it will not need to be reinitialized each time — blizz
– blizz, Commented Mar 1, 2014 at 16:40

VladL · Accepted Answer · 2014-03-03 08:06:14Z

4

Then you must have the instance of the list somewhere else, take it outside of the function :)

List<int[]> arrayList = new List<int[]>();

public void Add(int Id , int Quantity )
{
    int[] buying = new int[] { Id, Quantity };
    //AddTo(buying);

    arrayList.Add(buying);
}

It is better to use the KeyValuePair instead of the int[]:

List<KeyValuePair<int, int>> arrayList = new List<KeyValuePair<int, int>>();
public void Add(int Id , int Quantity )
{
    KeyValuePair<int, int> buying = new KeyValuePair<int, int>(Id, Quantity);
    arrayList.Add(buying);
}

or if you don't need the specific order, you are better to use the Dictionary:

Dictionary<int, int> list = new Dictionary<int, int>();

public void Add(int Id , int Quantity )
{
   list.add(Id, Quantity);
}

edited Mar 3, 2014 at 8:06

answered Mar 1, 2014 at 16:39

VladL

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Comments

OSborn · Accepted Answer · 2014-03-01 16:41:22Z

2

So your problem is that when the function ends, arrayList is no longer accessible. One way to solve this is by giving arrayList class scope, the other is to send it to the function (declaring in the class or in another function)

public void Add(List<int[]> list, int Id , int Quantity )
{
    int[] buying = new int[] { Id, Quantity };

    list.Add(buying);
}

answered Mar 1, 2014 at 16:41

OSborn

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Selman Genç · Accepted Answer · 2014-03-01 16:44:37Z

1

Define your list inside of your class ?

List<int[]> arrayList = new List<int[]>();
public void Add(int Id , int Quantity )
{
    int[] buying = new int[] { Id, Quantity };
    //AddTo(buying);

    arrayList.Add(buying);
}

BTW, you should consider using a class that contains Id and Quantity properties.Or instead of List<int[]> you can use a Dictionary<int,int> which the key would be Id and Value is Quantity.

edited Mar 1, 2014 at 16:44

answered Mar 1, 2014 at 16:39

Selman Genç

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Comments

Inisheer · Accepted Answer · 2014-03-01 16:41:46Z

0

In addition to the other answers. If you don't want the list specifically in your class, you can pass a list as a parameter to the method.

public void Add(int id, int quantity, List<int[]> container)
{
   int[] buying = new int[] { id, Quantity };
   container.Add(buying);
}

answered Mar 1, 2014 at 16:41

Inisheer

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Comments

Udit Narayan · Accepted Answer · 2014-03-01 16:44:38Z

0

Two ways

1. Either pass the reference of the list to this function.

public void Add(List<int[]> arrayList, int Id , int Quantity )
{    
int[] buying = new int[] { Id, Quantity };
arrayList.Add(buying);
}

In this ways you can always add the items to the existing one list.

2. Or, this add function must be part of the class say XYZ. So create

List arrayList;

as the member of the class and use the following snippet.

class XYZ {

List arrayList;

public XYZ() { this.arrayList = new List(); }

public void Add(List arrayList, int Id , int Quantity ) {
int[] buying = new int[] { Id, Quantity };
this.arrayList.Add(buying);   }
}

answered Mar 1, 2014 at 16:44

Udit Narayan

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