Dictionary<(Of <(TKey, TValue>)>) 当TKey是类时，如何让ContainerKey正确？

[msys200]

    class Program
    {
        static void Main(string[] args)
        {
            Dictionary<A, string> dic = new Dictionary<A, string>();
            A ta = new A();
            ta.a = "a";
            dic[ta] = "b";
            A test = new A();
            test.a = "a";
            Console.WriteLine(dic.ContainsKey(test)); //这里输出的是false
        }
    }

    public class A
    {
        public string a;
    }

[msys200]

我想要输出时true的

[zhujiazhi]

http://social.microsoft.com/Forums/es-ES/visualcshartzhchs/thread/de37d6b2-4ee4-4029-8a6a-99ff2c0cdc67

[wartim]

Console.WriteLine(dic.ContainsKey(ta));
ta 和 test 已经不是同一个了

[ljhcy99]

这样呢？
Dictionary<A, string> dic = new Dictionary<A, string>();
A ta = new A();
ta.a = "a";
dic[ta] = "b";
A test = ta;
Console.WriteLine(dic.ContainsKey(test)); //这里输出的是false