看到笔试题目c#1128

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

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
string str = "天工问答，是天工网旗下专业的免费知识问答平台，帮助建设行业从业者解决在学习和工作中遇到的实际问题，让建筑人不再有疑问";
Dictionary<char, int> dic = new Dictionary<char, int>();
for (int i = 0; i < str.Length; i++)
{
if (!dic.ContainsKey(str[i]))
{
dic[str[i]] = 1;
}
else
{
dic[str[i]]++;
}

}
int maxvalue = dic.Values.Max();
foreach (char c in dic.Keys)
{
if(dic[c]==maxvalue)
{
Console.WriteLine(c);
Console.ReadKey();
}
}

}
}
}