String a ="1234";
String c = "123"; c+="4";

Console.WriteLine((object)a==(object)c);     //False
Console.WriteLine((object)a.Equals((object)c)); //True
Console.WriteLine(a==c); //True
Console.WriteLine(a.Equals(c)); //True

有谁详细解释一下四个bool值为什么是这样的原因