IComparable<T> Vs. IComparer<T> System.Comparison<T>

最新推荐文章于 2025-09-12 16:49:27 发布

转载最新推荐文章于 2025-09-12 16:49:27 发布 · 71 阅读

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本文探讨了IComparable<T>与IComparer<T>的区别及应用。IComparable<T>用于对象自身与其他同类型对象的比较，而IComparer<T>则适用于不同对象间的比较，常用于集合排序。文章通过具体示例展示了这两种接口的实现方式。

Well they are not quite the same thing as IComparer<T> is implemented on a type that is capable of comparing two different objects while IComparable<T> is implemented on types that are able to compare themselves with other instances of the same type.

I tend to use IComparable<T> for times when I need to know how another instance relates to this instance. IComparer<T> is useful for sorting collections as the IComparer<T> stands outside of the comparison.

IComparer < T >是上实现一种能够比较两个不同的对象而IComparable < T >是上实现类型能够比较自己与其他相同类型的实例。

class Student : IComparable { public string Name { get; set; } public int MathScore { get; set; } public int EnglishScore { get; set; } public int TotalScore { get { return this.MathScore + this.EnglishScore; } } public int CompareTo(object obj) { return CompareTo(obj as Student); } public int CompareTo(Student other) { if (other == null) { return 1; } return this.Name.CompareTo(other.Name); } }

But if a teacher 'A' wants to compare students based on MathScore, and teacher 'B' wants to compare students based on EnglishScore. It will be good idea to implement IComparer separately. (More like a strategy pattern)

class CompareByMathScore : IComparer<Student> { public int Compare(Student x, Student y) { if (x.MathScore > y.MathScore) return 1; if (x.MathScore < y.MathScore) return -1; else return 0; } }

public class NameComparer:IComparer<Student>
{
public int Compare(Student x, Student y)
{
return x.Name.CompareTo(y.Name);
}
}

 http://stackoverflow.com/questions/3498891/system-comparisont-understanding

System.Comparison<T> is defined as follows:

public delegate int Comparison<in T>(T x, T y);

That means that it's delegate, not a class. A method accepting a delegate as a parameter actually accepts a method, not an instance of a Comparison class.

This code can be rewritten as follows with a lambda expression:

collection.Sort((i1, i2) => i1.ToString().CompareTo(i2.ToString()));

The following snippet might explain better what happens:

public static class TestClass { public static void Main(string[] args){ Comparison<Int32> comparisonDelegate = CompareWithCase; //We now can use comparisonDelegate as though it is a method; int result = comparisonDelegate(1,2); } public static int CompareWithCase(int i1, int i2) { return i1.ToString().CompareTo(i2.ToString()); } }