How to extend array's in C#

Question

I have to do an exercise using arrays.

The user must enter 3 input (each time, information about items) and the inputs will be inserted in the array

Then i must to display the array.

The difficulty i face is that i don't know how to increase the array's length without changing the information within it and how to allow the user to enter another information again?

public string stockNum;
public string itemName;
public string price;

string[] items = new string[3];

public string [] addItem(string[] items)
{
    System.Console.WriteLine("Please Sir Enter the stock number");
    stockNum = Console.ReadLine();
    items.SetValue(stockNum, 0);
    System.Console.WriteLine("Please Sir Enter the price");
    price = Console.ReadLine();
    items.SetValue(price, 1);
    System.Console.WriteLine("Please Sir Enter the item name");
    itemName = Console.ReadLine();
    items.SetValue(itemName, 2);
    Array.Sort(items);
    return items;
}


public void ShowItem()
{
    addItem(items);
    Console.WriteLine("The stock Number is " + items[0]);
    Console.WriteLine("The Item name is " + items[2]);
    Console.WriteLine("The price " + items[1]);
}

static void Main(string[] args)
{
    DepartmentStore depart = new DepartmentStore();
    string[] ar = new string[3];
    // depart.addItem(ar);
    depart.ShowItem();
}

1. How can i allow the user to enter more than on input of information .. for example, the first time the user will enter the information about item ( socket number, price and name) .. how can i make the user enter another information about other item ?

2. hHow can i display the socket num, price and name for each item in the array, if i suppose to have more than one item in the array ?

Answer 1

Try using System.Collections.Generic.List this provides a resizable collection which also has a ToArray() method to return an ordinary array if you need it.

Answer 2

Can you use ArrayList instead? It will resize as needed.

Answer 3

Use a list, and then convert to an array.

In fact, in this example, you should have a class or struct for StockInfo {stock number, price, item name}, then you should enter the data into a List. Finally, you could convert to StockInfo[] by using the ToArray method of the list.

Answer 4

I think you may be going about the problem wrong...

Consider that the three items (stock number, price, and name) are part of a larger object. For now we can just call it item. We want to store a number of items in a list or array. Consider using an object-oriented approach like this:

class Widget
{
  public int StockNum;
  public int Price;
  public string Name;

  Widget(stockNum, price, name)
  {
    this.StockNum= stockNum;
    this.Price = price;
    this.Name = name;
  }
}

Now, you can can instantiate a list of these objects:

List<Widget> items = new List<Widget>();

And add items to them:

for (int i = 0; i < 5; i++)
{
  //Get input from user
  System.Console.WriteLine("Please Sir Enter the stock number");
  stockNum= Convert.ToInt32(Console.ReadLine()); //This isn't very safe...

  System.Console.WriteLine("Please Sir Enter the price");
  price = Convert.ToInt32(Console.ReadLine()); //This isn't very safe...

  System.Console.WriteLine("Please Sir Enter the item name");
  name = Console.ReadLine();

  //Then add it to a new object
  Widget item = new Widget(stockNum, price, name);

  //And add this item to a list
  items.Add(item);
}

Answer 5

Assuming your assignment requires you to use Arrays and not other collection classes, then you will have to do things the hard way.

Arrays are immutable, that is you cannot change them after they have been created. You can change the contents, but not the size of the array. If you need to grow or shrink the array, you will have to create a new array with the new number of items, then copy the items you want from the old array to the new array.

For instance, suppose you want to take an array and only copy the even elements.

int[] a = new int[] {0,1,2,3,4,5,6,7,8,9};
int[] a2 = new int[a.Length / 2];
int counter = 0;
for (int i = 0; i < a.Length; i = i + 2)
{
    a2[counter++] = a[i];
}

Then, you could always assign a2 back to a

a = a2;