自己写的替换文件的内容,瞎写的,能用

public void ReplaceString(string TargetString, string NewString)
{
    string FileSrc = System.Web.HttpContext.Current.Server.MapPath("../admin/TextFile1.txt");
    if (File.Exists(FileSrc))
    {
        StreamReader sr = File.OpenText(FileSrc);
        string srrow = null;
        //读取文件所有的内容
        srrow = sr.ReadToEnd();
        if (srrow.IndexOf(TargetString) != -1)
        {
            //找到要找的字符串
            var a = srrow.IndexOf(TargetString);
            //要找的字符串后第一个"位置
            var b = srrow.IndexOf(""", a);
            //要找的字符串后第二个"位置
            var c = srrow.IndexOf(""", b + 1);
            //第一个"及之前的字符串
            string subtop = srrow.Substring(0, b + 1);
            //第二个"之后的字符串
            string subbottom = srrow.Substring(c);
            //拼接
            NewString = subtop + NewString + subbottom;
            //Response.Write(sub);
        }
        sr.Close();
        //写入
        StreamWriter sw = new StreamWriter(FileSrc, false);
        sw.WriteLine(NewString);
        sw.Close();
    }