关于StreamWriter.writeline()

Question

TXT的操作，覆盖和删除都是一样的，需要重写一次。
用StringBuilder把需要的字符连起来后，重新覆盖整个文本。

Answer 1

string File_path = Application.StartupPath + @"\test.txt";
            FileStream fs = new FileStream (File_path,FileMode .OpenOrCreate );
            fs.Close();
            StreamReader sr = new StreamReader(File_path);
            StringBuilder sb = new StringBuilder();
            
            while (sr.Peek() >= 0)
            {
                string geteach = sr.ReadLine();
                sb.Append(geteach);
                if (geteach == "case")
                {
                    sb.Append("overwrite");
                    //or break;
                    break;                 
                }
            }            sr.Close();
            StreamWriter sw = new StreamWriter(File_path,true);
            sw.WriteLine(sb.ToString ());
            sw.Close();