虽然a==b，但ab的地址是不一样的。

 

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            //定义字符串变量a
            string a = "1234";
            //定义字符串变量b
            string b = "1234";
            StringBuilder sb = new StringBuilder();
            StringBuilder sc = new StringBuilder();
            sc.Append("123").Append(@"sf");
            sb.Append("123").Append(@"sf").ToString();
            //查看对象引用
            Console.WriteLine(object.ReferenceEquals(a, b));
            Console.WriteLine(Object.ReferenceEquals(a, b));
            Console.WriteLine(a == b);
            Console.WriteLine(a.GetHashCode());
            Console.WriteLine(b.GetHashCode());
            Console.WriteLine(sb.GetHashCode());
            Console.WriteLine(sc.GetHashCode());
        }
    }
}