使用计时器逐行读取文本文件

Question

StreamReader sr = new StreamReader("C:/CR EZ Test/Log.txt");    //use with IF
private void timer2_Tick(object sender, EventArgs e)
{
    if ((line = sr.ReadLine()) != null)
    {   
        //FileStream fs = File.Open("C:/CR EZ Test/Log.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
        //StreamReader sr = new StreamReader(fs); //use with While can't use with }else{
        //while ((line = sr.ReadLine()) != null) 
        //{
        string[] dataLog = line.Split(new[] { ',' }, StringSplitOptions.None);
        mpa = (dataLog[1]);
        ml  = (dataLog[2]);
        lph = (dataLog[3]);
        elapsedTime = float.Parse(dataLog[4]) / 1000;

        if (testStatus > 0) time = elapsedTime.ToString("0.0");
        tb2.Value = int.Parse(dataLog[6]);

        if (chart1.Series[0].Points.Count > tb1.Value && tb1.Value > 0)
        {
            chart1.Series[0].Points.RemoveAt(0);
            chart1.Series[1].Points.RemoveAt(0);
        }
        chart1.Series[0].Points.AddXY(dataLog[5], int.Parse(dataLog[1]));
        chart1.Series[1].Points.AddXY(dataLog[5], int.Parse(dataLog[6]));
        //}
    }
    else
    {
        sr.DiscardBufferedData();
        sr.BaseStream.Seek(0, SeekOrigin.Begin);
        sr.BaseStream.Position = 0;
        //sr.Close();
        //alertTB.Text = "";
        timer2.Enabled = false;
    }
    alertTB.ForeColor = Color.Red;
    alertTB.Text = "Data Log Viewing In Progress";
}

问题是我正在通过 GUI 读取充满变量的文本文件，就像重播视频一样。如代码所示，它可以工作，我可以控制计时器滴答声来改变重播速度。问题是文件正在使用中，所以我无法在文件使用时写入或删除文本，除非先关闭它。我想要么能够找到 Streamreader 的解决方法，要么使用 Filestream to Streamreader 代码，这样我就可以在文件使用时对其进行编辑。问题是，我不知道如何让它与计时器一起工作，它只是非常快速地读取整个文件。非常感谢任何帮助或想法。

这里的问题是如何将注释掉的代码：

读取一行文本文件，
让计时器计时
然后读取文本文件的下一行，依此类推。显然在数据到达时对其进行处理。

Answer 1

打开正在使用的文件

我想你要找的是 FileStream 和 FileShare.ReadWrite 的 StreamReader 实例（不是你注释掉的实例）,

var fs = new FileStream("C:\foo.txt", FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
var sr = new StreamReader(fs);

设置流的位置

根据您的评论，您似乎在定位流时遇到了问题，这就是您可以做到的...

fs.Position = 0; // note this is the FileStream not the StreamReader!
// alternatively, you could use Seek

顺序访问和随机访问的区别

最后，您可能想看看下面的内容，看看顺序访问和随机访问之间的区别

一个潜在的解决方案

这是一个名为 FileMonitor 的 class，它将检查文件并在文件更改/更新时更新列表。

我知道你想要一个计时器来轮询文本文件中的数据，但是为了防止计时器非常快，我已经优化了 FileMonitor 来观察文件的变化并且只在有变化时提取是一个变化。

Please note that this only continues to read where it was left off, based on the position of the stream. So, it will not work if lines are deleted or modified prior to getting "extracted". This means it only functions based on your requirements and is not improved to handle a lot of other scenarios, but it should adequately cover your requirements.

public class FileMonitor : IDisposable
{
    private readonly FileStream _file;
    private readonly StreamReader _reader;

    private long _position;
    private List<string> _lines;

    public FileMonitor(string file)
    {
        if (String.IsNullOrEmpty(nameof(file))) throw new ArgumentNullException(nameof(file));

        _lines = new List<string>();

        FileSystemWatcher watcher = new FileSystemWatcher();
        watcher.Path = Path.GetDirectoryName(file);
        watcher.Filter = Path.GetFileName(file);
        watcher.NotifyFilter = NotifyFilters.LastAccess | NotifyFilters.LastWrite | NotifyFilters.FileName | NotifyFilters.DirectoryName;
        watcher.Changed += new FileSystemEventHandler(OnChanged);
        //watcher.Created += new FileSystemEventHandler(OnCreated);
        //watcher.Deleted += new FileSystemEventHandler(OnDeleted);
        //watcher.Renamed += new RenamedEventHandler(OnRenamed);

        // begin watching.
        watcher.EnableRaisingEvents = true;

        // begin reading
        _file = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
        _reader = new StreamReader(_file);
        _lines = ReadLines(_reader).ToList();
        _position = _file.Position;
    }

    private void OnChanged(object source, FileSystemEventArgs e)
    {
        List<string> update = ReadLines(_reader).ToList();
         // fix to remove the immidate newline
        if (update.Count() > 0 && String.IsNullOrEmpty(update[0])) update.RemoveAt(0);
        _lines.AddRange(update);
        _position = _file.Position;

        // just for debugging, you should remove this
        Console.WriteLine($"File: {e.FullPath} [{e.ChangeType}]");
    }

    public IEnumerable<string> Lines { get { return _lines; } }

    public void Reset()
    {
        _file.Position = 0;
        _position = _file.Position;
        _lines.Clear(); 
    }

    private static IEnumerable<string> ReadLines(StreamReader reader)
    {
        string line;
        while ((line = reader.ReadLine()) != null)
        {
            yield return line;
        }
    }

    public void Dispose()
    {
        _reader.Dispose();
        _file.Dispose();
    }
}

这里是你如何将它与你的计时器一起使用

private IEnumerable<string> _lines; // holds all the lines "extracted"

void Main()
{
    string file = @"C:\Data\foo.txt";

    using (var timer = new System.Timers.Timer())
    {
        timer.Interval = 2000; // 2 second interval
        timer.Elapsed += OnTimedEvent; // attach delegate
        timer.Enabled = true; // start the timer    

        // open the file
        using (var monitor = new FileMonitor(file))
        {
            _lines = monitor.Lines;

             // loop forever, remove this
            while (true) { }
        }
    }
}

public void OnTimedEvent(object sender, EventArgs e)
{
    // just for debugging, you should remove this
    Console.WriteLine($"current count: {_lines.Count()}");
}

如果不清楚，提取的数据保存在字符串列表中。在上面，您可以使用 monitor.Line 属性.

从监视器中获取 "extracted" 数据

Answer 2

一个行之有效的解决方案

 string line;
        if (!File.Exists(logFile))
        {
            viewLog.Text = "Play";
            alertTB.ForeColor = Color.Red;
            alertTB.Text = "File Does Not Exist | Log Data To Create File";
            chart.Text = "Scope On";
        }

        if (File.Exists(logFile))
        {
            var lineCount = File.ReadLines(logFile).Count();//read text file line count to establish length for array
            if (lineCount < 2)
            {
                viewLog.Text = "Play";
                alertTB.ForeColor = Color.Red;
                alertTB.Text = "File Exists | No Data Has Been Recorded";
                chart.Text = "Scope On";
            }

            if (counter < lineCount && lineCount > 0)//if counter is less than lineCount keep reading lines
            {
                line = File.ReadAllLines(logFile).Skip(counter).Take(lineCount).First();

                string[] dataLog = line.Split(new[] { ',' }, StringSplitOptions.None);
                //-----------------------------------------Handling my data 
                counter++;
            }
            else
            {
                counter = 0;
                timer2.Enabled = false;
            }
        }

这是我找到的修复方法，它允许编辑文件或删除文件的内容。在尝试加载文件之前我得到了行数。然后我使用计数器遍历这些行。我可以根据计时器滴答间隔更改下一行读取之间的延迟、暂停或停止它。

使用计时器逐行读取文本文件

Read text file line by line using timer

c#

streamreader

datalog

打开正在使用的文件

设置流的位置

顺序访问和随机访问的区别

一个潜在的解决方案

一个行之有效的解决方案