IComparable and IComparer

 using System; using System.Collections.Generic; using System.Text; using System.Collections; namespace Sample_IComparable_and_IComparer { /// <summary> /// Course Enum 課程枚舉 /// </summary> public enum CourseEnum { Chinese =0, Math, English, Total } /// <summary> /// Scores class 分數類，用於記錄學生的分數 /// </summary> public class Scores { int[] score = new int[4]; public int this[CourseEnum course] { get { return score[(int)course]; } set { score[(int)course] = value; } } public override string ToString() { StringBuilder sbScore = new StringBuilder(); sbScore.Append("Chinese:"); sbScore.Append(score[0]); sbScore.Append(" "); sbScore.Append("Math:"); sbScore.Append(score[1]); sbScore.Append(" "); sbScore.Append("English:"); sbScore.Append(score[2]); sbScore.Append(" "); sbScore.Append("Total:"); sbScore.Append(score[3]); return sbScore.ToString(); } } /// <summary> /// Student Class 繼承 IComparable。IComparable接口定義了類型的自然排序方式。 /// </summary> public class StudentComparable : IComparable { string name; Scores score = new Scores(); public StudentComparable(string name, int chinese, int math, int english) { this.name = name; this.score[CourseEnum.Chinese] = chinese; this.score[CourseEnum.Math] = math; this.score[CourseEnum.English] = english; this.score[CourseEnum.Total] = chinese + math + english; } public string Name { get { return this.name; } set { this.name = value; } } public Scores Score { get { return this.score; } set { this.score = value; } } //顯示實現接口,該方法在類型上不夠安全。必須檢查參數的運行時類型 //此方法要執行裝箱和拆箱來進行實際的比較 //用此方法。如果Student[] student = new Student[99999];或者更大的時候，就知道“爽”就一個字了。 int IComparable.CompareTo(object obj) { if (obj is StudentComparable) { StudentComparable s = obj as StudentComparable; return this.CompareTo(s);//升序。 //return this.CompareTo(s) * -1;//降序。 } throw new ArgumentException("obj is not a StudentComparable"); } //爲接口中的方法提供一個公有的強類型重載版本 //優點：強類型，方便（至少能少打幾個字母-_-#） public int CompareTo(StudentComparable stu) { //執行 String.CompareTo 方法 (String) //此方法性能優於CompareTo(object obj)方法 //很明顯String.CompareTo 方法 (String) 沒有拆箱 return this.name.CompareTo(stu.name); } public override string ToString() { return this.name + " : " + this.score.ToString(); } } /// <summary> /// StudentComparer Class。繼承 IComparer。IComparer則爲類型提供了另外的排序方式。 /// </summary> public class StudentComparer : IComparer { StudentComparable[] sc; CourseEnum course; int IComparer.Compare(object x, object y) { if(!(x is StudentComparable)) throw new ArgumentException("obj is not a StudentComparable"); if(!(y is StudentComparable)) throw new ArgumentException("obj is not a CourseEnum"); StudentComparable left = x as StudentComparable; StudentComparable right = x as StudentComparable; return Compare(left, right); } public int Compare(StudentComparable left, StudentComparable right) { return left.Score[course].CompareTo(right.Score[course]); //升序 //return left.Score[course].CompareTo(right.Score[course]) * -1; //降序 } public StudentComparable[] Sc { get { return sc; } set { sc = value; } } public StudentComparer(StudentComparable[] sc, CourseEnum course) { this.sc = sc; this.course = course; } public override string ToString() { return sc.ToString(); } } /// <summary> /// Test Class /// </summary> public class TestClass { public static void Main() { Console.WriteLine("***** IComparable 根據姓名排序*****/n"); StudentComparable[] student = new StudentComparable[4]; student[0] = new StudentComparable("C", 60, 80, 80); student[1] = new StudentComparable("A", 70, 70, 70); student[2] = new StudentComparable("D", 90, 90, 90); student[3] = new StudentComparable("B", 80, 100, 100); Array.Sort(student);//調用 int IComparable.CompareTo(object obj) foreach (StudentComparable stu in student) { Console.WriteLine(stu); } StudentComparable[] student2 = new StudentComparable[2]; student2[0] = new StudentComparable("A", 80, 80, 80); student2[1] = new StudentComparable("B", 70, 70, 70); //調用 public int CompareTo(Student stu) Console.WriteLine("/n/"{0}/".CompareTo(/"{1}/") : {2}", student2[0].Name, student2[1].Name, student2[0].CompareTo(student2[1])); Console.WriteLine("/n/n***** IComparer 根據總成績排序 *****/n"); StudentComparer sc = new StudentComparer(student, CourseEnum.Total); Array.Sort(sc.Sc, sc.Compare);//調用 public int Compare(StudentComparable left, StudentComparable right) foreach (StudentComparable s in sc.Sc) { Console.WriteLine(s.ToString()); } Console.WriteLine("/n/n***** IComparer 根據語文成績排序 *****/n"); StudentComparer sc2 = new StudentComparer(student, CourseEnum.Chinese); Array.Sort(sc2.Sc, sc2.Compare); foreach (StudentComparable s in sc2.Sc) { Console.WriteLine(s.ToString()); } Console.Read(); } } }//namespace

 

結果如下：

***** IComparable 根據姓名排序*****

A : Chinese:70   Math:70   English:70   Total:210
B : Chinese:80   Math:100   English:100   Total:280
C : Chinese:60   Math:80   English:80   Total:220
D : Chinese:90   Math:90   English:90   Total:270

"A".CompareTo("B") : -1

***** IComparer 根據總成績排序 *****

A : Chinese:70   Math:70   English:70   Total:210
C : Chinese:60   Math:80   English:80   Total:220
D : Chinese:90   Math:90   English:90   Total:270
B : Chinese:80   Math:100   English:100   Total:280

***** IComparer 根據語文成績排序 *****

C : Chinese:60   Math:80   English:80   Total:220
A : Chinese:70   Math:70   English:70   Total:210
B : Chinese:80   Math:100   English:100   Total:280
D : Chinese:90   Math:90   English:90   Total:270