Dictionary.ContainsKey return False, but a want True

Question

namespace Dic { public class Key {     string name;     public Key(string n) { name = n; } }  class Program {     static string Test()     {         Key a = new Key("A");         Key b = new Key("A");         System.Collections.Generic.Dictionary<Key, int> d = new System.Collections.Generic.Dictionary<Key, int>();         d.Add(a, 1);         return d.ContainsKey(b).ToString();     }      static void Main(string[] args)     {         System.Console.WriteLine(Test());     } } } 

What should I change to get true?

Answer 1

You want true - but a and b are different objects.

You need to override GetHashCode and Equals on class Key

public class Key {     string name;     public Key(string n) { name = n; }      public override int GetHashCode()     {         if (name == null) return 0;         return name.GetHashCode();     }      public override bool Equals(object obj)     {         Key other = obj as key;         return other != null && other.name == this.name;     } }