c＃如何创建动态列表/数组

Question

Actually, I have this :

public ArrayList _albumId;
public ArrayList _albumName;
public ArrayList _nbPhotos;

And when I have a new album, I add a line on each ArrayList. Do you know something to do it with only one list or array ? Thanks

Answer 1

First of all, don't use ArrayList - use generic List<T> .

Second - instead of having separate list for each attribute of album, create Album class with all required attributes, and keep albums in List<Album> :

public class Album
{
   public int Id { get; set; }
   public string Name {get; set; }
   public int CountOfPhotos {get; set; }
}

Adding new album:

_albums.Add(new Album { Id = 2, Name = "Foo", CountOfPhotos = 42 });

Where albums list declared as

List<Album> _albums = new List<Album>();

Answer 2

Why keep information about the same thing broken apart into multiple arrays?

Create an Album object. Something like:

public class Album
{
    public int ID { get; set; }
    public string Name { get; set; }
    // other properties, etc.
}

And have a list of albums :

var albums = new List<Album>();

When adding a new album, add a new album:

var newAlbum = new Album
{
    ID = someValue,
    Name = anotherValue
}
albums.Add(newAlbum);

Keep information about an object encapsulated within that object, not strewn about in other disconnected variables.

---

As an analogy, consider the act of parking a car in a parking lot. With a collection of objects, the parking lot has a collection of spaces and each car goes into a space. Conversely, with separate arrays of values, the process for parking a car is:

1. Take the car apart.
2. Put the tires in the tire space, the windows in the window space, the doors in the door space, etc.
3. When you want to get the car back, go around to all the spaces and find your parts. (Hope that you found the right ones.)
4. Re-build the car.

Modeling encapsulated objects just makes more sense.

Answer 3

Use a generic list.

Define a class, for smaple:

public class Album
{
   public int Id { get; set; }
   public string Name { get; set; }
   public string[] AlbumPhotos { get; set; }
}

And use it in a generic list:

var albums = new List<Album>();

albums.Add(new Album() { Id = 1, Name = "Ramones" };
albums.Add(new Album() { Id = 2, Name = "Leave Home" };
albums.Add(new Album() { Id = 3, Name = "Rocket To Russia" };