写入文件读取操作

Question

I have to read text file that has millions of records. while reading file I have to implement something like "Tracker" which will write last read LineNumber to log file. I don't want this log file open and write operation affect my application performance. can anyone suggest me how to implement it? PS I am using yield to read this big file, and I have multiple files like that. I want to stop reading operation if file has some invalid record...While this read operation is going on I want to somehow want to let end users know that so far it has read so and so number of line - file read is in progress.

    using (StreamReader reader = new StreamReader(_fileNameAndPath))
                {
                    while (reader.EndOfStream == false)
                    {
                        string data = reader.ReadLine();

                        _fileLineNumber = _fileLineNumber + 1;
  //this line number should go to tracker file Logger.Trace(_fileLineNumber )

                       //............
                     }
                }

Logger class :

public static class Logger 
{     
      .....
      public static void Trace(string message)
      {
          FileStream fileStream = new FileStream(logFilePath, FileMode.Append);
          StreamWriter streamWriter = new StreamWriter(fileStream);
          streamWriter.WriteLine(message); 
      }

}

Answer 1

You could store your file stream as a class-level private field, open it before you enter your loop, then close it after you exit the loop.

Or better yet, implement IDisposable on Logger , and wrap your loop inside a using statement, and all the cleanup will take place automatically:

public class Logger : IDisposable
{
    private FileStream fileStream;
    private StreamWriter streamWriter;

    public void Trace(string message)
    {
        streamWriter.WriteLine(message);
    }

    public Logger(string logFilePath)
    {
        fileStream = new FileStream(logFilePath, FileMode.Append);
        streamWriter = new StreamWriter(fileStream);
    }

    public void Dispose()
    {
        streamWriter.Dispose();
        fileStream.Dispose();
    }
}

here is how you would use it within the code you have:

var logFilePath = ""; // replace this with however you get your log path.

using (var logger = new Logger(logFilePath))
{
    while (reader.EndOfStream == false)
    {
        string data = reader.ReadLine();
        _fileLineNumber= _fileLineNumber + 1;
        logger.Trace(_fileLineNumber);
    }
}

Answer 2

Clearly, I don't know what you're really trying to make but I suppose a best way to save that logging stuff is to write the file after your entire process. So, you can create an array of number and store that array once the process is done.

var readLines = new List<number>();

using (StreamReader reader = new StreamReader(_fileNameAndPath))
{
    while (reader.EndOfStream == false)
    {
        string data = reader.ReadLine();
        readLines.Add(_fileLineNumber);

        _fileLineNumber = _fileLineNumber + 1;
    }
}

Logger.Trace(readLines.ToString());