List<object>排序 z

一般我們在撰寫程式時，很常會使用到List<>來裝取自定義的類別陣列，跟一般的陣列插在哪呢?!好處是什麼?!好處就是一般的陣列需要先 宣告長度，而List<>不用，所以在資料個數不一的時候我們可能比較會使用List<>來裝載資料，並且依序地呈現給使用者 看，所以List<>的排序就變得將當重要了!

本篇文章將引導您將List<object>排序。

以身高為範例，首先我們先自定義一個類別用來放在List<>中用的。

   1:  public class TallItem{

   2:      public string name { set; get; }

   3:      public int Height { set; get; }

   4:  }

再來將個別的身高資料放入List<>中

   1:  public void InitialTallItem() {

   2:      List<TallItem> list_tallItems = new List<TallItem>();

   3:      list_tallItems.Add(new TallItem() { name = "Tony", Height = 180 });

   4:      list_tallItems.Add(new TallItem() { name = "Jorden", Height = 200 });

   5:      list_tallItems.Add(new TallItem() { name = "Nono", Height = 155 });

   6:      list_tallItems.Add(new TallItem() { name = "Jessica", Height = 166 });

   7:  }

再來是排序

   1:  list_tallItems.Sort((x, y) => { return -x.Height.CompareTo(y.Height); });

所以全部大概長這樣:

   1:  public void InitialTallItem() {

   2:      List<TallItem> list_tallItems = new List<TallItem>();

   3:      list_tallItems.Add(new TallItem() { name = "Tony", Height = 180 });

   4:      list_tallItems.Add(new TallItem() { name = "Jorden", Height = 200 });

   5:      list_tallItems.Add(new TallItem() { name = "Nono", Height = 155 });

   6:      list_tallItems.Add(new TallItem() { name = "Jessica", Height = 166 });

   7:   

   8:      list_tallItems.Sort((x, y) => { return -x.Height.CompareTo(y.Height); });

   9:   

  10:      for (int i = 0; i < list_tallItems.Count; i++) {

  11:          Debug.WriteLine(list_tallItems[i].name + ":" + list_tallItems[i].Height);

  12:      }

  13:  }

顯示的結果會是這樣:

   1:  Jorden:200

   2:  Tony:180

   3:  Jessica:166

   4:  Nono:155

如此一來List<TallItem>就經過排序囉，並且是由高到低排序。

除此之外也可以使用Linq語法來排序，此方法有點像在下SQL資料庫的語法，也比較淺顯易懂

   1:  List<TallItem> list_tallItems = new List<TallItem>();

   2:  list_tallItems.Add(new TallItem() { name = "Tony", Height = 180 });

   3:  list_tallItems.Add(new TallItem() { name = "Jorden", Height = 200 });

   4:  list_tallItems.Add(new TallItem() { name = "Nono", Height = 155 });

   5:  list_tallItems.Add(new TallItem() { name = "Jessica", Height = 166 });

   6:   

   7:  //依 身高 做遞增排序  

   8:  list_tallItems = list_tallItems.OrderBy(x => x.Height).ToList();

   9:  foreach (TallItem item in list_tallItems)

  10:  {

  11:      Debug.WriteLine(item.name + ":" + item.Height);

  12:  }

  13:  Debug.WriteLine("================================");

  14:  //依 身高 做遞減排序  

  15:  list_tallItems = list_tallItems.OrderByDescending(x => x.Height).ToList();

  16:  foreach (TallItem item in list_tallItems)

  17:  {

  18:      Debug.WriteLine(item.name + ":" + item.Height);

  19:  }

結果會像這樣:

   1:  Nono:155

   2:  Jessica:166

   3:  Tony:180

   4:  Jorden:200

   5:  ================================

   6:  Jorden:200

   7:  Tony:180

   8:  Jessica:166

   9:  Nono:155