dynamically increase of the number of elements in an array

Question

I'm trying to create a dynamic array which starts with 3 elements. I want to use addColumn to add an element to string[] name. But I guess the the addColumn function is not doing what I expected.What do I need to archieve that functionality? I guess I need saomething like "name.addElement()"?

class LogData
{
    private string[] name;
    private int numberOfColumns;

     public LogData()
     {
         name = new string[3];
         numberOfColumns = name.Length;    
     }

     public void addColumn()
     {
         name = new string[1];// Thats not working, after calling, the number of columns is still 3
     }

     public int getNumberofcolumns()
     {
         return numberOfColumns;
     }
}

I call in the main fucntion:

LogData logData = new LogData();

Console.Write(logData.getNumberofcolumns() + "\n");
logData.addColumn();
Console.Write(logData.getNumberofcolumns() + "\n");

Console.Write("done...\n\n");
Console.ReadLine();

The output is:

3
3
done...

Use a `List<>` if you want to add items. If you finally need an array use `list.ToArray()`. — Tim Schmelter, Feb 12 '16 at 08:42
Think about `List` which offers everything you need automatically... — Shnugo, Feb 12 '16 at 08:43
Similar: https://stackoverflow.com/questions/4840802/change-array-size — SiD, Feb 12 '16 at 08:58

Dmitry Bychenko · Accepted Answer · 2016-02-12T08:45:24.967

2

Are you lloking for

  public void addColumn() {
    Array.Resize(ref name, name.Length + 1);
  }

But, IMHO, a better solution is to change String[] to List<String>:

  class LogData
  {
    private List<String> name = new List<String>();

    ...
    public void addColumn() {
      name.Add(null);
    }

edited Feb 12 '16 at 08:45

answered Feb 12 '16 at 08:43

Dmitry Bychenko

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does this function just add one element to the array? – xy36 Feb 12 '16 at 08:44
@xy36: it *resizes* the array and in case items are *added* they will be `null`s – Dmitry Bychenko Feb 12 '16 at 08:46
Thats nice. I assume all data in the "old" array will stay the same? – xy36 Feb 12 '16 at 08:47
@xy36: yes, the old data will be preserved – Dmitry Bychenko Feb 12 '16 at 08:48
Do I miss something? My compiler cant find the add-function. – xy36 Feb 12 '16 at 09:00
@xy36: `Add` function is declared in `List` only, so in case of `private List name` you can use `Add` and in case of `private string[] name` - not – Dmitry Bychenko Feb 12 '16 at 10:05

score 1 · Answer 2 · answered Feb 12 '16 at 08:43

1

Use List<string> instead of the array.

answered Feb 12 '16 at 08:43

Bewar Salah

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score 1 · Answer 3 · answered Feb 12 '16 at 08:44

1

You only assign the number of columns once, it doesn't get the length of the name whenever you call it, the whole field is pointless

 public int getNumberofcolumns()
 {
     return name.Length;
 }

Note: Of course, a list would be preferred.

answered Feb 12 '16 at 08:44

Sayse

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score 1 · Answer 4 · answered Feb 12 '16 at 08:45

You should use a List<string> which offers you a ton of libraries for manipulating it, and it covers all your requirements. here's the doc

Usage:

List<string> names = new List<string>();

//adding an item
names.Add('YourString');
//getting the length
names.Count();

dynamically increase of the number of elements in an array

4 Answers4