using System;
using System.Collections.Generic;
using System.Text;
//2005控制台

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
string str = "abcdecfgchicgckclcmcn";
int position = str.IndexOf('c');
string newStr = str.Substring(0, position) + 'P' + str.Substring(position + 1);
Console.WriteLine(position);
Console.WriteLine(newStr);
Console.Read();
}
}
}

string q="010070004083904160200300070020096508005030700608400020050007003097803250100040080";
要将第3位的0换成2
直接使用
q[2]='2';就行了
在C#中可以将字符串直接像字符数组那样进行操作