Develop Reference

Concurrent file access

I am running multiple instances of an application that reads first line from a file, then it deletes the first line and saves the file under the same name. I found out that in some instances the applications will crash. I created a sample program just to better understand the issues I have.
If I run four instances of this program, sometimes multiple instances attempt to delete the same line. In the end the operation succeeds, but it is not efficient. How can I improve the code to avoid this? Perhaps each instance needs to lock the file while it uses it.
using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;
using System.IO;
using System.Threading;
using System.Diagnostics;
namespace ConcurrentFileAccess
{
public partial class MainForm : Form
{
bool gbAbort = false;
public MainForm()
{
InitializeComponent();
}
void BtnCreateFileClick(object sender, EventArgs e)
{
string sFile = #"S:\Temp\concurrentFileAccess.txt";
Stopwatch stopwatch = Stopwatch.StartNew();
if (File.Exists(sFile)) {
File.Delete(sFile);
}
if (!File.Exists(sFile)) {
List<string> list = new List<string>();
var fc = File.Create(sFile);
fc.Close();
for (int i = 1; i <= 200; i++) {
list.Add(i.ToString());
}
File.WriteAllLines(sFile, list);
listBox1.Items.Add("File " + sFile + " was created and it contains 200 lines");
} else {
string[] lines = File.ReadAllLines(sFile);
int nlines = lines.Length;
listBox1.Items.Add("File " + sFile + " already exists and it contains " + nlines + " lines");
}
stopwatch.Stop();
listBox1.Items.Add("File created in " + stopwatch.Elapsed.ToString("hh\\:mm\\:ss\\.fff"));
}
void BtnDeleteFromFileClick(object sender, EventArgs e)
{
gbAbort = false;
int nlines = 9999;
while (nlines > 0) {
nlines = DeleteOneLine();
Application.DoEvents();
if (gbAbort) {
return;
}
}
}
int DeleteOneLine()
{
string sFile = #"S:\Temp\concurrentFileAccess.txt";
listBox1.Items.Add("We are in DeleteLines()...");
listBox1.SelectedIndex = listBox1.Items.Count - 1;
Application.DoEvents();
int nLinesLeft = 9999;
string line0 = string.Empty;
Stopwatch stopwatch = Stopwatch.StartNew();
int ntry = 0;
while (ntry < 100) {
try {
string[] lines = File.ReadAllLines(sFile);
List<string> list = new List<string>(lines);
nLinesLeft = list.Count;
if (nLinesLeft > 0) {
line0 = list[0];
list.RemoveAt(0);
listBox1.Items.Add("Deleted line " + line0);
listBox1.SelectedIndex = listBox1.Items.Count - 1;
Application.DoEvents();
listBox1.Items.Add("Writing to file after line " + line0 + " was deleted");
File.WriteAllLines(sFile, list);
nLinesLeft = list.Count;
Application.DoEvents();
} else {
nLinesLeft = 0;
break;
}
} catch (Exception) {
ntry++;
listBox1.Items.Add("ntry = " + ntry + ", could not delete line " + line0 + " from file. Attempting again...");
listBox1.SelectedIndex = listBox1.Items.Count - 1;
Application.DoEvents();
Application.DoEvents();
Thread.Sleep(50);
}
}
if(ntry >= 100) {
nLinesLeft = -1; // should never get here
}
stopwatch.Stop();
listBox1.Items.Add("ntry: " + ntry + ", lines Left: " + nLinesLeft + ", elapsed = " + stopwatch.Elapsed.ToString("hh\\:mm\\:ss\\.fff"));
listBox1.SelectedIndex = listBox1.Items.Count - 1;
Application.DoEvents();
return nLinesLeft;
}
void BtnAbortClick(object sender, EventArgs e)
{
gbAbort = true;
}
void BtnOpenAppFolderClick(object sender, EventArgs e)
{
string sFile = Application.ExecutablePath;
string sPath = Path.GetDirectoryName(sFile);
Process.Start(sPath);
}
void BtnOpenFileClick(object sender, EventArgs e)
{
string sFile = #"S:\Temp\concurrentFileAccess.txt";
if(File.Exists(sFile)) {
Process.Start(sFile);
}
else {
MessageBox.Show("File " + sFile + " not found");
}
}
}
}

how to capture real time stream data in csv or .data file in a windows form Application

I implemented a function in a windows form application to capture and read needed tabular data from a file (sourcedata.data) and save it in another file (result.data ).
How i and by using the application can capture a real time stream data like such available here :https://data.sparkfun.com/streams in csv or .data file to use it.
Or are there any direct waya to read the stream data directly from the website source periodically ?
private void button5_Click(object sender, EventArgs e)
{
List<string[]> rows = new List<string[]>();
int[] indexes = { 0, 1, 3, 5, 6, 7, 8, 9 };
using (var reader = new StreamReader(#"sourcedata.data"))
{
using (StreamWriter writetext = new StreamWriter("result.data"))
{
while (!reader.EndOfStream)
{
var line = reader.ReadLine();
if (line.IndexOf(',') == -1)
continue;
string[] values = line.Split(',');
string[] row = new string[indexes.Length];
int insertIndex = 0;
for (int i = 0; i < values.Length; i++)
{
string val = values[i];
if (val.Trim() == "?")
goto BREAK;
if (indexes.Contains(i))
row[insertIndex++] = val;
}
rows.Add(row);
writetext.WriteLine(String.Join(",", row));
BREAK:;
}
}
}
}

You have two split your problem into two separated sub problems:
Write a method public static string DownloadData(...) which will download the data from the source. This can be done by any HTTP client or library you can find like System.Net.Http.HttpClient or System.Net.WebClient.
See How to download a file from a URL in C#?
Add/start a timer which calls this method periodically. You can use classes like System.Windows.Forms.Timer or System.Timers.Timer.
See What is the best way to implement a "timer"?

#Progman
It is the code
public partial class Download : Form
{
public Download()
{
InitializeComponent();
}
WebClient client;
private void btnDownload_Click(object sender, EventArgs e)
{
string url = txtUrl.Text;
if (!string.IsNullOrEmpty(url))
{
Thread thread = new Thread(() =>
{
Uri uri = new Uri(url);
string filename = System.IO.Path.GetFileName(uri.AbsolutePath);
client.DownloadFileAsync(uri, Application.StartupPath + "/" + filename);
});
thread.Start();
}
}
private void Download_Load(object sender, EventArgs e)
{
client = new WebClient();
client.DownloadProgressChanged += Client_DownloadProgressChanged;
client.DownloadFileCompleted += Client_DownloadFileCompleted;
}
private void Client_DownloadFileCompleted(object sender, AsyncCompletedEventArgs e)
{
MessageBox.Show("Download Completed.", "Message", MessageBoxButtons.OK, MessageBoxIcon.Information);
}
private void Client_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
{
Invoke(new MethodInvoker(delegate ()
{
progressBar.Minimum = 0;
double recieve = double.Parse(e.BytesReceived.ToString());
double total = double.Parse(e.TotalBytesToReceive.ToString());
double percentage = recieve / total * 100;
lblStatus.Text = $"Download {string.Format("{0:0.##}", percentage)}%";
progressBar.Value = int.Parse(Math.Truncate(percentage).ToString());
}));
}
}

c# Progressbar, Overflow returns negative value

I'm creating a backup application. I have 5 folders in different locations what needs to be copied to one backup folder. (solved via checkbox.checked)
The main issue is that some of the folders are more than 3-4GB in total (with all subfolders) Progressbar is not updated because "maxbyte" returns a negative value. (I assume int32 overflows after 2gb file copy)
(Sorry can't explain it more in details..I'm just a beginner C# programmer)
using System;
using System.ComponentModel;
using System.Linq;
using System.Windows.Forms;
using System.IO;
using memoQClientBackuTool;
namespace memoQBackupTool
{
public partial class BGWorker : Form
{
public BGWorker()
{
InitializeComponent();
}
BackgroundWorker bw;
string source = "";
string target = "";
bool isfile = false;
int filecount = 0;
int currentFileNr = 1;
string newFilename = "";
int maxbytes = 0;
public void ShowProgress(string from, string to, bool isf)
{
InitializeComponent();
source = from;
target = to;
isfile = isf;
bw = new BackgroundWorker();
bw.DoWork += new DoWorkEventHandler(bw_DoWork);
bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged);
bw.WorkerReportsProgress = true;
bw.WorkerSupportsCancellation = true;
GetFileData();
}
private void GetFileData()
{
if (isfile)
{
FileInfo fi = new FileInfo(source);
maxbytes = Convert.ToInt32(fi.Length);
//
//set progress bar length
//
progressBar1.Minimum = 0;
progressBar2.Minimum = 0;
progressBar1.Maximum = maxbytes;
progressBar2.Maximum = 1;
bw.RunWorkerAsync();
}
else
{
GetDirectoryInfo(source);
//
//set progress bar length
//
progressBar1.Minimum = 0;
progressBar2.Minimum = 0;
progressBar1.Maximum = maxbytes;
progressBar2.Maximum = filecount;
bw.RunWorkerAsync();
}
}
private void GetDirectoryInfo(string source)
{
string[] files = Directory.GetFiles(source);
foreach (string file in files)
{
FileInfo fi = new FileInfo(file);
maxbytes += Convert.ToInt32(fi.Length);
filecount += 1;
}
string[] folders = Directory.GetDirectories(source);
foreach (string folder in folders)
{
GetDirectoryInfo(folder);
}
}
void bw_DoWork(object sender, DoWorkEventArgs e)
{
if (isfile)
{
FileStream fs = new FileStream(source, FileMode.Open);
long FileSize = fs.Length;
FileInfo fi = new FileInfo(source);
byte[] bBuffer = new byte[(int)FileSize];
fs.Read(bBuffer, 0, (int)FileSize);
fs.Close();
UpdateLabels(fi.FullName);
newFilename = fi.Name;
try
{
FileStream fss = new FileStream(target + "\\" + newFilename, FileMode.CreateNew);
BinaryWriter biwr = new BinaryWriter(fss);
for (int i = 0; i < bBuffer.Length; i += 15000)
{
if (i + 15000 < bBuffer.Length)
{
biwr.Write(bBuffer, i, 15000);
bw.ReportProgress(15000);
}
else
{
biwr.Write(bBuffer, i, bBuffer.Length - i);
bw.ReportProgress(bBuffer.Length - i);
}
}
biwr.Close();
fss.Close();
} catch (IOException){
MessageBox.Show("Nincs olyan...");
}
}
else
{
string[] temp = source.Split('\\');
target += "\\" + temp[temp.Count() - 1];
DirectoryInfo s = new DirectoryInfo(source);
DirectoryInfo t = new DirectoryInfo(target);
CopyDirectory(s, t);
}
if (bw.CancellationPending)
{
e.Cancel = true;
return;
}
}
public void CopyDirectory(DirectoryInfo di_source, DirectoryInfo di_target)
{
if (Directory.Exists(di_target.FullName) == false)
{
Directory.CreateDirectory(di_target.FullName);
}
foreach (FileInfo fi in di_source.GetFiles())
{
newFilename = fi.Name;
FileStream fs = new FileStream(fi.FullName, FileMode.Open);
long FileSize = fs.Length;
byte[] bBuffer = new byte[(int)FileSize];
fs.Read(bBuffer, 0, (int)FileSize);
fs.Close();
UpdateLabels(fi.FullName);
if (File.Exists(di_target.ToString() + "\\" + fi.Name))
{
Random rand = new Random();
newFilename = newFilename + "_" + rand.Next(1, 10000);
}
FileStream fss = new FileStream(di_target.ToString() + "\\" + newFilename, FileMode.CreateNew);
BinaryWriter biwr = new BinaryWriter(fss);
for (int i = 0; i < bBuffer.Length; i += 500000)
{
if (i + 500000 < bBuffer.Length)
{
biwr.Write(bBuffer, i, 500000);
bw.ReportProgress(500000);
}
else
{
biwr.Write(bBuffer, i, bBuffer.Length - i);
bw.ReportProgress(bBuffer.Length - i);
}
}
biwr.Close();
fss.Close();
}
foreach (DirectoryInfo di_SourceSubDir in di_source.GetDirectories())
{
DirectoryInfo nextSubDir = di_target.CreateSubdirectory(di_SourceSubDir.Name);
CopyDirectory(di_SourceSubDir, nextSubDir);
}
}
void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
progressBar1.Value += e.ProgressPercentage;
int copied = progressBar1.Value / 1024;
int total = maxbytes / 1024;
lbl_kbscopied.Text = copied + "/" + total;
}
delegate void UpdateLabelsDelegate(string filename);
void UpdateLabels(string fname)
{
if (!InvokeRequired)
{
lbl_filename.Text = "Copying: " + fname;
lbl_filenr.Text = "File: " + currentFileNr + "/" + filecount;
currentFileNr++;
progressBar2.Value += 1;
}
else
{
Invoke(new UpdateLabelsDelegate(UpdateLabels), new object[] { fname });
}
}
private void button1_Click(object sender, EventArgs e)
{
Cursor.Current = Cursors.WaitCursor;
bw.CancelAsync();
}
private void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
{
if (e.Cancelled)
{
Cursor.Current = Cursors.Default;
CustomMsgBox.Show("The task has been canceled", "Error", "OK");
this.Close();
}
else if (e.Error != null)
{
MessageBox.Show("Error. Details: " + (e.Error as Exception).ToString());
}
else
{
this.Close();
}
}
}
}

Report progress not in absolute values, but in relative; percentage, for example.
Let say that 1MB file is 100% of progress bar. That means that you have to initialize it with 100: progressBar1.Maximum = 100. Then every 15000 bytes that were copied is a little bit more than 1%. Instead of bw.ReportProgress(15000) do bw.ReportProgress(1).

I will suggest to use long instead of int wherever you are getting total bytes copied/uploaded so far. If I understood your code you are using int in for loop where you call ReportProgress

How can i sum a changing values in int variable ? And what is the real number of directories on hard disk?

Backgroundworker dowork event
string CurrentFileWithPath;
private void _FileProcessingWorker_DoWork(object sender, DoWorkEventArgs e)
{
try
{
DirectoryInfo[] MySubDirectories = (DirectoryInfo[])e.Argument;
for (int i = 0; i < MySubDirectories.GetLength(0); i++)
{
DirectoryInfo MySubDirectory = MySubDirectories[i];
List<FileInfo> l = new List<FileInfo>();
CountFiles(MySubDirectory, l);
int totalFiles = l.Count;
object[] CurrentStatus = new object[5];
CurrentStatus[3] = i.ToString();
CurrentStatus[4] = totalFiles.ToString();
_FileProcessingWorker.ReportProgress(0, CurrentStatus);
string CurrentDirectory = "Current Directory: " + MySubDirectory.Name;
foreach (FileInfo MyFile in l)
{
CurrentStatus = new object[5];
if (_FileProcessingWorker.CancellationPending)
{
e.Cancel = true;
return;
}
if (MyFile.Extension.ToLower() == ".cs" || MyFile.Extension.ToLower() == ".vb")
{
string CurrentFile = "Current File: " + MyFile.Name;
string CurrentFileWithPath = MyFile.FullName;
CurrentStatus[0] = CurrentDirectory;
CurrentStatus[1] = CurrentFile;
_FileProcessingWorker.ReportProgress(0, CurrentStatus);
List<string> Result = SearchInFile(CurrentFileWithPath, "static class FileShellExtension");
if (Result != null && Result.Count > 0)
{
CurrentStatus[2] = Result;
_FileProcessingWorker.ReportProgress(0, CurrentStatus);
}
}
}
}
}
catch (Exception err)
{
return;
}
Progresschanged event
private void _FileProcessingWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
if (typeof(object[]) == e.UserState.GetType())
{
object[] StatusMsg = (object[])e.UserState;
if (5 == StatusMsg.GetLength(0))
{
label2.Text = StatusMsg[4].ToString();
label4.Text = StatusMsg[3].ToString();
if (StatusMsg[0] != null && StatusMsg[1] != null)
{
lblCurrentDirectory.Text = StatusMsg[0].ToString();
lblStatus.Text = StatusMsg[1].ToString();
}
if (StatusMsg[2] != null)
{
if (StatusMsg[2].GetType() == typeof(List<string>))
{
List<string> l = (List<string>)StatusMsg[2];
for (int i = 0; i < l.Count; i++)
{
ListViewCostumControl.lvnf.Items.Add("Directory: " + lblCurrentDirectory.Text + "In File: " + lblStatus.Text + l[i]);
w.WriteLine("Directory: " + lblCurrentDirectory.Text + "In File: " + lblStatus.Text + l[i]);
}
}
}
}
}
}
CountFiles method
private void CountFiles(DirectoryInfo di, List<FileInfo> l)
{
try
{
l.AddRange(di.EnumerateFiles());
}
catch
{
string fff = "";
}
try
{
IEnumerable<DirectoryInfo> subDirs = di.EnumerateDirectories();
if (subDirs.Count() > 0)
{
foreach (DirectoryInfo dir in subDirs)
CountFiles(dir, l);
}
}
catch
{
string yyy = "";
}
}
SearchInFile method
private List<string> SearchInFile(string fileToSearch, string textToSearch)
{
List<string> l = new List<string>();
try
{
foreach (var line in File.ReadAllLines(fileToSearch))
{
if (line.Contains(textToSearch))
l.Add(line);
}
}
catch(Exception err)
{
string fff = err.ToString();
}
return l;
}
The first problem is when getting the number of directories:
private void btnProcess_Click(object sender, EventArgs e)
{
btnProcess.Enabled = false;
btnDirectory.Enabled = false;
btnCancel.Visible = true;
btnCancel.Enabled = true;
btnCancel.Text = "Cancel";
MyProgressBar.Visible = true;
_FileProcessingWorker = new BackgroundWorker();
_FileProcessingWorker.WorkerReportsProgress = true;
_FileProcessingWorker.WorkerSupportsCancellation = true;
_FileProcessingWorker.DoWork += new DoWorkEventHandler(_FileProcessingWorker_DoWork);
_FileProcessingWorker.ProgressChanged += new ProgressChangedEventHandler(_FileProcessingWorker_ProgressChanged);
_FileProcessingWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(_FileProcessingWorker_RunWorkerCompleted);
string BasePath = lblDirectoryName.Text;
DirectoryInfo MyDirectory = new DirectoryInfo(BasePath);
DirectoryInfo[] MySubDirectories = MyDirectory.GetDirectories();
int SubDirectoryCount = MySubDirectories.GetLength(0);
MyProgressBar.Minimum = 0;
MyProgressBar.Step = 1;
MyProgressBar.Maximum = SubDirectoryCount;
MyProgressBar.Value = MyProgressBar.Minimum;
_LastCounter = 0;
_FileProcessingWorker.RunWorkerAsync(MySubDirectories);
}
In the click button i'm getting the sub directories.
But there are two problems.
In the dowork event when i put a break point on this line:
for (int i = 0; i < MySubDirectories.GetLength(0); i++)
I see that it contain 409 directories. But when i report the number of directories to the label4 in the dowork event
CurrentStatus[3] = i.ToString();
In the progresschanged event
label4.Text = StatusMsg[3].ToString();
I see in the end on label4 408 directories. And in D:(in this case i'm working on my D:\ directory) when i select all the directories in windows explorer make right click and properties i see only 405 directories. So what is the real number of directories ? What and how number of directories should i display in label4 ?
The second problem is when i report the number of files in dowork event:
CurrentStatus[4] = totalFiles.ToString();
And in progresschanged event show it on label2:
label2.Text = StatusMsg[4].ToString();
The problem is that the totalFiles value is changing all the time once it's 2 then it's 768 then it's 66 then 8987 but what i want to do is somehow to sum in real time the values in totalFiles so in label2 i will see first time for example: 2 then 770 then (770+66) so i will see in label2 816....to see always the sum of all the values so far.
The last problem is in the progresschanged event this loop:
for (int i = 0; i < l.Count; i++)
{ ListViewCostumControl.lvnf.Items.Add("Directory: " + lblCurrentDirectory.Text + "In File: " + lblStatus.Text + l[i]);
w.WriteLine("Directory: " + lblCurrentDirectory.Text + "In File: " + lblStatus.Text + l[i]);
}
It might be logic somehow to take out and make this loop at this time in the program in another backgroundworker like backgroundworker2 dowork event ? If so how to do it ? The problem is when the loop have many items to add to the listView it make the program to hang until the loop finish.

Each time you execute
CurrentStatus[4] = totalFiles.ToString();
You are resetting the status value to the count of files in the current processing directory. This is why the number keeps bouncing around. Instead I would suggest:
int thisDirFiles;
thisDirFiles = l.Count;
totalFiles += thisDirFiles;
CurrentStatus[4] = totalFiles.ToString();
Now when you report progress, CurrentStatus[4] will have the running total.
For your second question, it looks to me you are trying to do too much when you are reporting progress. Manipulating ListViews can be costly, and you are probably spending more time updating the ListView than you are processing the directories, so your machine seems to freeze.

Can't access file

I can't seem to get access to the file I'm working with in the program I'm writing. I'm not sure how exactly to work this since I want my program to open a file of your choice, which it does, then I want it to be able to take in info into an arrary, which it does, then from there, write that information from the array to the file you opened up. When I try some code to start working on it it tells me, "The process cannot access the file 'file' because it is being used by another process." Here is what I have so far. Please let me know. Thank you. The problematic areas is the Save_Click section of the code where I wrote "This is a test" Thanks.
public partial class ListingSearch : Form
{
string line;
DialogResult result;
string fileName;
int i = 0;
string[] first = new string[100];
string[] last = new string [100];
string[] phone = new string [100];
string[] grade = new string [100];
public ListingSearch()
{
InitializeComponent();
MessageBox.Show("Please be sure to open a file before beginning");
}
private void OpenFile_Click(object sender, EventArgs e)
{
using (OpenFileDialog filechooser = new OpenFileDialog())
{
result = filechooser.ShowDialog();
fileName = filechooser.FileName;
System.IO.StreamReader file =
new System.IO.StreamReader(fileName);
while ((line = file.ReadLine()) != null)
{
string[] words = File.ReadAllText(fileName).Split(new string[] { "\n", "\r\n", ":" }, StringSplitOptions.RemoveEmptyEntries);
//firstName.Text = words[4];
//lastName.Text = words[5];
//telephone.Text = words[6];
//GPA.Text = words[7];
}
Read.Enabled = true;
}
}
private void Save_Click(object sender, EventArgs e)
{
File.AppendAllText(fileName, "This is a test");
}
private void Read_Click(object sender, EventArgs e)
{
MessageBox.Show(fileName);
MessageBox.Show(File.ReadAllText(fileName));
}
private void info_Click(object sender, EventArgs e)
{
first[i] = firstName.Text;
firstName.Text = " ";
last[i] = lastName.Text;
lastName.Text = " ";
phone[i] = telephone.Text;
telephone.Text = " ";
grade[i] = GPA.Text;
GPA.Text = " ";
i++;
}
private void displayinfo_Click(object sender, EventArgs e)
{
if (i == 0)
MessageBox.Show("Nothing to display!");
else
for (int j = 0; j < i; j++)
{
MessageBox.Show(first[j] + " " + last[j] + "\r" + phone[j] + "\r" + grade[j]);
}
}

You get error here
File.ReadAllText(fileName)
because you open same file before it here
System.IO.StreamReader file = new System.IO.StreamReader(fileName);

You need to close the file after you are finished reading it. Also, not sure why you are opening the file at all, since you subsequently use File.ReadAllText which will handle opening and closing the file all on its own.
Seems like your OpenFile_click event should just look like this:
using (OpenFileDialog filechooser = new OpenFileDialog())
{
result = filechooser.ShowDialog();
fileName = filechooser.FileName;
string[] words = File.ReadAllText(fileName).Split(new string[] { "\n", "\r\n", ":" }, StringSplitOptions.RemoveEmptyEntries);
Read.Enabled = true;
}

You haven't closed your StreamReader. C# will lock the file until you do. Or you could use a StreamWriter after you closed your StreamReader