вот набрасал быстро
на форме две кнопки и textbox (первая стартует процесс, вторая cancel-ит). Больше ниче делать не надо (разве что имя файла поменять) 8-)
Для удобства работа вынесена в отдельный класс.
| Код |
public Form1()
{
InitializeComponent();
button2.Enabled = false;
button1.Click += button1_Click;
button2.Click += button2_Click;
}
TxtSlowReader _txtReader;
private void button1_Click(object sender, EventArgs e)
{
_txtReader = new TxtSlowReader("C:\\textfile.txt");
_txtReader.OnComplete += txtReader_OnComplete;
_txtReader.WorkAsync();
button1.Enabled = false;
button2.Enabled = true;
}
void txtReader_OnComplete(object sender, TxtSlowReaderEventArgs e)
{
button1.Enabled = true;
button2.Enabled = false;
if (e.Error != null)
MessageBox.Show(e.Error.ToString(), "ERROR!");
else if(e.Lines==null)
MessageBox.Show("Canceled!", "ok");
else if (e.Lines != null)
textBox1.Text = string.Join(", ", e.Lines);
}
private void button2_Click(object sender, EventArgs e)
{
if (null != _txtReader)
{
_txtReader.Abort();
_txtReader = null;
}
}
}
public class TxtSlowReaderEventArgs : EventArgs
{
public TxtSlowReaderEventArgs(Exception error, IList<string> lines)
{
this.Error = Error;
this.Lines = lines;
}
public Exception Error { get; private set; }
public IList<string> Lines { get; private set; }
}
public class TxtSlowReader
{
private string _filename;
private BackgroundWorker _bw;
public TxtSlowReader(string filename)
{
_filename = filename;
}
public void Abort()
{
lock (this)
{
if (_bw != null)
{
_bw.CancelAsync();
_bw = null;
}
}
}
public void WorkAsync()
{
_bw = new BackgroundWorker();
_bw.WorkerSupportsCancellation = true;
_bw.DoWork += bw_DoWork;
_bw.RunWorkerCompleted += bw_RunWorkerCompleted;
_bw.RunWorkerAsync();
}
void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (null != OnComplete)
{
if (e.Cancelled)
OnComplete(this, new TxtSlowReaderEventArgs(null, null));
else
OnComplete(this, new TxtSlowReaderEventArgs(e.Error, (IList<string>)e.Result));
}
}
void bw_DoWork(object sender, DoWorkEventArgs e)
{
List<string> rv = new List<string>();
using (var fs = new FileStream(_filename, FileMode.Open, FileAccess.Read))
{
using (var txtr = new StreamReader(fs))
{
string line;
while ((line = txtr.ReadLine()) != null)
{
lock (this)
{
if (_bw == null || _bw.CancellationPending) { rv = null; break; }
}
Thread.Sleep(200);
rv.Add(line);
}
}
}
e.Result = rv;
}
public event EventHandler<TxtSlowReaderEventArgs> OnComplete;
}
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