c# – 使用IEqualityComparer和Equals / GethashCode Override有

当我使用词典时,有时我必须更改默认的等同含义才能比较键.我看到,如果我重写关键字类上的Equals和GetHashCode,或者我创建一个实现IEqualityComparer的新类,我有相同的结果.那么使用IEqualityComparer和Equals / GethashCode Override有什么区别？
两个例子：

class Customer
{
    public string name;
    public int age;
    public Customer(string n,int a)
    {
        this.age = a;
        this.name = n;
    }
    public override bool Equals(object obj)
    {
        Customer c = (Customer)obj;
        return this.name == c.name && this.age == c.age;
    }
    public override int GetHashCode()
    {
        return (this.name + ";" + this.age).GetHashCode();
    }
}
  class Program
{
    static void Main(string[] args)
    {
        Customer c1 = new Customer("MArk",21);
        Customer c2 = new Customer("MArk",21);
        Dictionary<Customer,string> d = new Dictionary<Customer,string>();
        Console.WriteLine(c1.Equals(c2));
        try
        {
            d.Add(c1,"Joe");
            d.Add(c2,"hil");
            foreach (KeyValuePair<Customer,string> k in d)
            {
                Console.WriteLine(k.Key.name + " ; " + k.Value);
            }
        }
        catch (ArgumentException)
        {
            Console.WriteLine("Chiave già inserita in precedenza");
        }
        finally
        {
            Console.ReadLine();
        }
    }
}

}

第二个 ：

class Customer
{
    public string name;
    public int age;
    public Customer(string n,int a)
    {
        this.age = a;
        this.name = n;
    }
}
class DicEqualityComparer : EqualityComparer<Customer>
{
    public override bool Equals(Customer x,Customer y) // equals dell'equalitycomparer
    {
        return x.name == y.name && x.age == y.age;
    }
    public override int GetHashCode(Customer obj)
    {
        return (obj.name + ";" + obj.age).GetHashCode();
    }
}
class Program
{
    static void Main(string[] args)
    {
        Customer c1 = new Customer("MArk",21);
        DicEqualityComparer dic = new DicEqualityComparer();
        Dictionary<Customer,string>(dic);
        Console.WriteLine(c1.Equals(c2));
        try
        {
            d.Add(c1,string> k in d)
            {
                Console.WriteLine(k.Key.name + " ; " + k.Value);
            }
        }
        catch (ArgumentException)
        {
            Console.WriteLine("Chiave già inserita in precedenza");
        }
        finally
        {
            Console.ReadLine();
        }
    }
}

}

两个例子都有相同的结果.

提前致谢.

interface ICustom
{
    int Key { get; set; }
}
class Custom : ICustom
{
    public int Key { get; set; }
    public int Value { get; set; }
}
class Another : ICustom
{
    public int Key { get; set; }
}

class DicEqualityComparer : IEqualityComparer<ICustom>
{
    public bool Equals(ICustom x,ICustom y)
    {
        return x.Key == y.Key;
    }

    public int GetHashCode(ICustom obj)
    {
        return obj.Key;
    }
}

var a = new Custom { Key = 1,Value = 2 };
var b = new Custom { Key = 1,Value = 2 };
var c = new Custom { Key = 2,Value = 2 };
var another = new Another { Key = 2 };

var d = new Dictionary<ICustom,string>(new DicEqualityComparer());

d.Add(a,"X");
// d.Add(b,"X"); // same key exception
d.Add(c,"X");
// d.Add(another,"X"); // same key exception