C#的List實現IComparer接口排序實例

背景

在C#中，若是想要爲List 實現排序，那麼須要實現一個接口 IComparer接口，從而根據接口中定義的方法來進行排序。
在這裏給出關於 IComparer的官方參考文檔 IComparer參考文檔

在這裏我本身經過對分數進行以下的規則排序:

• 首先按照chinese分數排序；
• chinese分數相同就按照math分數排序；
• math分數也相同的話就按照English分數排序；

代碼實現

// 分數排序
public class Score
{
	private int chinese;
	private int math;
	private int english;

	public Score(int ch, int math, int eng)
	{
		chinese = ch;
		this.math = math;
		english = eng;
	}

	public bool IsSame(Score score)
	{
		if (chinese == score.chinese && english == score.english && math == score.math)
		{
			return true;
		}
		return false;
	}

	public int Chinese
	{
		get
		{
			return chinese;
		}
		set
		{
			if (value != chinese)
				chinese = value;
		}
	}

	public int English
	{
		get
		{
			return english;
		}
		set
		{
			if (value != english)
				english = value;
		}
	}

	public int Math
	{
		get
		{
			return math;
		}
		set
		{
			if (value != math)
				math = value;
		}
	}
}

public class ScoreComparer : IComparer<Score>
{
	public int Compare(Score x, Score y)
	{
		if (x.IsSame(y))
		{
			return 0;
		}

		// compare chinese score firstly
		if (x.Chinese > y.Chinese)
		{
			return 1;
		}
		else if (x.Chinese < y.Chinese)
		{
			return -1;
		}

		// if chinese score is same, we should compare math score secondly
		if (x.Math > y.Math)
		{
			return 1;
		}
		else if (x.Math < y.Math)
		{
			return -1;
		}

		// if chinese and math are same, we should compare english score finally
		if (x.English > y.English)
		{
			return 1;
		}
		else if (x.English < y.English)
		{
			return -1;
		}

		return 0;
	}
}

public class TestSort
{
	public static void Test()
	{
		List<Score> ts = new List<Score>();

		// init ts with some score
		ts.Add(new Score(80, 88, 45));
		ts.Add(new Score(80, 86, 45));
		ts.Add(new Score(83, 85, 90));
		ts.Add(new Score(83, 85, 40));
		ts.Add(new Score(89, 88, 49));
		ts.Add(new Score(76, 89, 49));
		ts.Add(new Score(73, 88, 49));
		ts.Add(new Score(73, 82, 49));

		// before sort output all elements in ts
		Console.WriteLine("Before sort, all score as follows: chinese\tmath\tenglish\t\n");
		foreach (var val in ts)
		{
			Console.WriteLine("\t\t\t\t\t" + val.Chinese + "\t" + val.Math + "\t" + val.English + "\n");
		}

		// after sort output all elements in ts
		SortScore(ts);
		Console.WriteLine("After sort, all score as follows: chinese\tmath\tenglish\t\n");
		foreach (var val in ts)
		{
			Console.WriteLine("\t\t\t\t\t" + val.Chinese + "\t" + val.Math + "\t" + val.English + "\n");
		}

	}

	public static void SortScore(List<Score> scoreList)
	{
		scoreList.Sort(new ScoreComparer());
	}
}

在代碼中關於IComparer接口的定義中實現有返回值的肯定，在這我給出官方的接口定義代碼，從註釋中能夠知道返回值表明什麼意義：

namespace System.Collections.Generic
{
    //
    // Summary:
    //     Defines a method that a type implements to compare two objects.
    //
    // Type parameters:
    //   T:
    //     The type of objects to compare.
    public interface IComparer<in T>
    {
        //
        // Summary:
        //     Compares two objects and returns a value indicating whether one is less than,
        //     equal to, or greater than the other.
        //
        // Parameters:
        //   x:
        //     The first object to compare.
        //
        //   y:
        //     The second object to compare.
        //
        // Returns:
        //     A signed integer that indicates the relative values of x and y, as shown in the
        //     following table.Value Meaning Less than zero x is less than y.Zero x equals y.Greater
        //     than zero x is greater than y.
        int Compare(T x, T y);
    }
}

輸出結果

Before sort, all score as follows: chinese      math    english

                                        80      88      45

                                        80      86      45

                                        83      85      90

                                        83      85      40

                                        89      88      49

                                        76      89      49

                                        73      88      49

                                        73      82      49

After sort, all score as follows: chinese       math    english

                                        73      82      49

                                        73      88      49

                                        76      89      49

                                        80      86      45

                                        80      88      45

                                        83      85      40

                                        83      85      90

                                        89      88      49