StringBuilder aa = new StringBuilder();
string bb = "123456789a";
aa.Append(bb.Substring(0,6));
aa.Append("ok");
aa.Append(bb.Substring(8));
var cc = aa.ToString();输出:123456ok9a
string bb = "123456789a";
aa.Append(bb.Substring(0,6));
aa.Append("ok");
aa.Append(bb.Substring(8));
var cc = aa.ToString();输出:123456ok9a
则a.Substring(0,5)+你替换的值+a.Substring(8,a.Length)附注:你得保证a的长度大于等于8,所以前面最好加上判断
if(a.Length>=8)
char[] ch = s.ToCharArray();
s[6] = 'a';
s[7] = 'b';
string result = new string(ch);
Console.WriteLine(result);
static void Main(string[] args)
{
Console.WriteLine("请输入一段字符串:");//提示输入
string strOld = Console.ReadLine();//记录输入的整段字符串
Console.Write("请输入要替换的字符串:");//提示输入
string strTemp = Console.ReadLine();//记录要替换的字符串
Console.Write("请输入替换为的字符串:");//提示输入
string strReplace = Console.ReadLine();//记录替换为的字符串
string strNew = strOld.Replace(strTemp, strReplace);//替换字符串
Console.WriteLine("原字符串:" + strOld);//输出原字符串
Console.WriteLine("新字符串:" + strNew);//输出新字符串
Console.ReadLine();
}