C# 如何在文本文件中只写一行

我有两个文本文件

bala.txt

和

bala1.txt

bala.txt

逐行包含如下文本：

balamurugan,rajendran,chendurpandian
christopher
updateba

 ba

bala1.txt

逐行包含如下文本：

balamurugan,rajendran,chendurpandian
christopher
updateba

 ba

在这里，我需要用

bala.txt

检查

bala1.txt

，并将其写入日志文件

Pattern Name:ba
LineNo : 1 : balamurugan,rajendran,chendurpandian
LineNo : 3 : updateba

现在是这样写的

 Pattern Name :ba
LineNo : 1 : balamurugan,rajendran,chendurpandian
LineNo : 2 : christopher
Pattern Name :ba
LineNo : 3 : updateba

这是我的密码

while ((line = file.ReadLine()) != null)
                                    {
              if (line.IndexOf(line2,StringComparison.CurrentCultureIgnoreCase) != -1)
                    dest.WriteLine("Pattern Name :" + line2);
                    dest.WriteLine("LineNo : " + counter.ToString() + " : " + line);
                                        counter++;
                                    }
                                    file.BaseStream.Seek(0, SeekOrigin.Begin);
                                        //(0, SeekOrigin.Begin);
                                    counter = 1;

---

我不知道如何只写一次模式名ba…有什么建议吗？？？

要对代码进行最少的更改，您可以这样更改：

        bool patternwritten = false;
        while ((line = file.ReadLine()) != null)
                                {
          if (line.IndexOf(line2,StringComparison.CurrentCultureIgnoreCase) != -1)
                if( !patternwritten){
                  dest.WriteLine("Pattern Name :" + line2);
                  patternwritten = true;
                }
                dest.WriteLine("LineNo : " + counter.ToString() + " : " + line);
                                    counter++;
                                }
                                file.BaseStream.Seek(0, SeekOrigin.Begin);
                                    //(0, SeekOrigin.Begin);
                                counter = 1;

---

要对代码进行最少的更改，可以如下所示进行更改：

        bool patternwritten = false;
        while ((line = file.ReadLine()) != null)
                                {
          if (line.IndexOf(line2,StringComparison.CurrentCultureIgnoreCase) != -1)
                if( !patternwritten){
                  dest.WriteLine("Pattern Name :" + line2);
                  patternwritten = true;
                }
                dest.WriteLine("LineNo : " + counter.ToString() + " : " + line);
                                    counter++;
                                }
                                file.BaseStream.Seek(0, SeekOrigin.Begin);
                                    //(0, SeekOrigin.Begin);
                                counter = 1;