Develop Reference

Reading Linked Text File From Resources with StreamReader

I have seen many examples that show StreamReader taking the arugment "Properties.Resources.someTextFile, and apparently they work great. However, in .net 4.5 I still get:
//while not end of file, read lines of file and split into array
string myFile = Properties.Resources.data;
string line;
StreamReader reader = new StreamReader(myFile);
while ((line = reader.ReadLine()) != null)
{
string[] array = line.Split('#');
string tickerSymbol = array[0];
string regPattern = array[1];
....
So, what am I doing wrong?

By accessing the data text file resource through Properties.Resources the resulting variable myFile should contain the string contents of the file.
string myFile = Properties.Resources.data;
var lines = myFile.Split(new[] { Environment.NewLine }, StringSplitOptions.None);
foreach(var line in lines)
{
// Process each line...
}

Replace data/value of csv file

I want to count the number of some strings and store it into a csv file. I've tried it but I don't know if this is the correct way and in addition, there are two problems.
First of all, here is my method:
public void CountMacNames(String macName)
{
string path = #"D:\Counter\macNameCounter.csv";
if (!File.Exists(path))
{
File.Create(path).Close();
}
var lines = File.ReadLines(path);
foreach (var line in lines)
{
bool isExists = line.Split(',').Any(x => x == macName);
if (isExists)
{
// macName exists, increment it's value by 1
}
else
{
// macName does not exists, add macName to CSV file and start counter by 1
var csv = new StringBuilder();
var newLine = string.Format("{0},{1}", macName, 1);
csv.AppendLine(newLine);
File.WriteAllText(path, csv.ToString());
}
}
}
The first problem is this IOException:
The process cannot access the file 'D:\Counter\macNameCounter.csv'
because it is being used by another process.
The second problem is, that I don't know how to increment the value by one, if a macName exists in the csv file (see first comment)
EDIT: Example for method "CountMacNames" call:
CountMacNames("Cansas");
CountMacNames("Wellback");
CountMacNames("Newton");
CountMacNames("Cansas");
CountMacNames("Princet");
Then, the CSV file should contain:
Cansas, 2
Wellback, 1
Newton, 1
Princet, 1

OK, this is what I'd do:
public void CountMacNames(String macName)
{
string path = #"D:\Counter\macNameCounter.csv";
// Read all lines, but only if file exists
string[] lines = new string[0];
if (File.Exists(path))
lines = File.ReadAllLines(path);
// This is the new CSV file
StringBuilder newLines = new StringBuilder();
bool macAdded = false;
foreach (var line in lines)
{
string[] parts = line.Split(',');
if (parts.Length == 2 && parts[0].Equals(macName))
{
int newCounter = Convert.ToIn32(parts[1])++;
newLines.AppendLine(String.Format("{0},{1}", macName, newCounter));
macAdded = true;
}
else
{
newLines.AppendLine(line.Trim());
}
}
if (!macAdded)
{
newLines.AppendLine(String.Format("{0},{1}", macName, 1));
}
File.WriteAllText(path, newLines.ToString());
}
This code does this:
Read all the lines from file only if it exists - otherwise we start a new file
Iterate over all the lines
If the first part of a 2-part line equals the mac, add 1 to counter and add line to output
If the first part doesn't match or the line format is wrong, add the line to output as is
If we didn't find the mac in any line, add a new line for the mac with counter 1
Write the file back

You can't read and write to the same file at the same time (in a simple way).
For small files, there are already answers.
If your file is really large (too big to fit in memory) you need another approach:
Read input file line by line
optinally modify the current line
write line to a temporary file
If finished delete input file, rename temporary file

For the first problem you can either read all the lines into memory and work there then write it all out again, or use streams.
using (FileStream fs = File.Open(filePath, FileMode.Create, FileAccess.ReadWrite))
{
var sw = new StreamWriter(fs);
var sr = new StreamReader(fs);
while(!streamReader.EndOfStream)
{
var line = sr.ReadLine();
//Do stuff with line.
//...
if (macExists)
{
//Increment the number, Note that in here we can only replace characters,
//We can't insert extra characters unless we rewrite the rest of the file
//Probably more hassle than it's worth but
//You could have a fixed number of characters like 000001 or 1
//Read the number as a string,
//Int.Parse to get the number
//Increment it
//work out the number of bytes in the line.
//get the stream position
//seek back to the beginning of the line
//Overwrite the whole line with the same number of bytes.
}
else
{
//Append a line, also harder to do with streams like this.
//Store the current position,
//Seek to the end of the file,
//WriteLine
//Seek back again.
}
}
}

You need to read the file in and release it, like this, to avoid the IO exception:
string[] lines = null;
using (var sr = new System.IO.StreamReader(path))
lines = sr.ReadToEnd().Split(new string[] {"\r", "\n"}, StringSplitOptions.RemoveEmptyEntries);
As for the count, you can just add an int value, change the method return type as int, too.
public int CountMacNames(String macName, String path)
{
if (!File.Exists(path))
{
File.Create(path).Close();
}
string[] lines = null;
using (var sr = new System.IO.StreamReader(path))
lines = sr.ReadToEnd().Split(new string[] {"\r", "\n"}, StringSplitOptions.RemoveEmptyEntries);
return lines.Where(p => p.Split(',').Contains(macName)).Count();
}
and inside the method that calls it:
var path = #"<PATH TO FILE>";
var cnt = CountMacNames("Canvas", path);
if (cnt > 0)
{
using (var sw = new StreamWriter(path, true, Encoding.Unicode))
sw.WriteLine(string.Format("Canvas,{0}", cnt));
}
Now, var res = CountMacNames("Canvas","PATH"); will return 2, and the lines "Canvas,2" or "Newton,1" will be appended to the file, without overwriting it.

How to terminate reading from text file when file is empty

When I run my program and there is data in my text file it works as I intended. However, the program crashes if the text file is empty. Therefore, I was wondering how I remedy this issue.
Here is my code for reading from text file:
//This method reads the order data from a text file and assigns the values to each object's variables
void Read_Order_Data()
{
FileStream fs = new FileStream("i:\\OrderData.txt", FileMode.Open, FileAccess.Read);
StreamReader reader = new StreamReader(fs);
while (!reader.EndOfStream)
{
string line = reader.ReadLine();
string[] fields = line.Split('#');
Order[Number_Of_Orders].Order_Number = fields[0];
Order[Number_Of_Orders].Type_Of_Bean = fields[1];
Order[Number_Of_Orders].Quantity_Of_Order = fields[2];
Order[Number_Of_Orders].Date_Of_Purchase = fields[3];
Number_Of_Orders++;
}//end of while statement
reader.Close();
}//end of Read_Order_Data()
If the text file is empty my program stops on this line:
Order[Number_Of_Orders].Type_Of_Bean = fields[1];
When it stops it says Type_Of_Bean is null.
Thanks for any assistance you can offer.

Change your while loop a bit:
string line;
while ((line = reader.ReadLine()) != null)
{
string[] fields = line.Split('#');
...
}
line will be null if the end of the input stream has been reached.
A simpler option may be to use Peek(). I modified the MSDN's example for StreamReader a tiny bit:
string line;
while (reader.Peek() >= 0)
{
line = reader.ReadLine();
...
}
Peek() will return -1 if there are no characters to be read (empty file).
And as others have suggested, make sure your split string array result has the number of fields you plan on indexing. If it doesn't, it might suggest a problem with the file you're reading.

Replace This:
string[] fields = line.Split('#');
With This:
string[] fields = line.Split(new []{'#'},StringSplitOptions.RemoveEmptyEntries);

You should add checking for length of fields in your code, like this:
...
string[] fields = line.Split(new[] {'#'}, StringSplitOptions.RemoveEmptyEntries);
if (fields.Length < 4) break;
...

you can check if field have the correct length
void Read_Order_Data()
{
FileStream fs = new FileStream("i:\\OrderData.txt", FileMode.Open, FileAccess.Read);
StreamReader reader = new StreamReader(fs);
while (!reader.EndOfStream)
{
string line = reader.ReadLine();
string[] fields = line.Split('#');
if (fields.length == 4){
Order[Number_Of_Orders].Order_Number = fields[0];
Order[Number_Of_Orders].Type_Of_Bean = fields[1];
Order[Number_Of_Orders].Quantity_Of_Order = fields[2];
Order[Number_Of_Orders].Date_Of_Purchase = fields[3];
Number_Of_Orders++;
}
}//end of while statement
reader.Close();
}//end of Read_Order_Data()

You can also do
string[] lines = System.IO.File.ReadAllLines("File");
foreach (var line in lines)
{
string[] fields = line.Split('#');
}

If you file is empty, then the following line
string[] fields = line.Split('#');
will give you a string array with only one element (empty string).
Which means that when trying to access the second element (fields[1]), your code will raise an exception.
Short story: you should check the size of the fields array before accessing it.

You can enumerate a line at a time without having to buffer the entire contents like so:
foreach (string line in File.ReadLines("i:\\OrderData.txt"))
{
string[] fields = line.Split('#');
if (fields.Length < 4) // You might also need to add this.
continue;
...
If the file is empty, it will not even enter the body of the loop. It also does not make a copy of the entire file in memory - only one line is buffered in memory at once.

C# windows forms application:How can I replace a single line in a textfile without deleting the original file?

I am making a project that uses streamreader and streamwriter, Is it possible that I only replace or save a text in an specific line only without affecting the other lines?
if I make like this
streamreader sr = new streamreader(#"txtfile");
list<string> lines = new list<string>();
while (!sr.EndOfStream)
sr.readline();
{
lines.Add(sr.ReadLine();
}
//put in textbox
sr.close();
{
streamwriter sw = new streamwriter(#"txtfile");
sw.WriteLine(textBox1.text);
sw.close();
}
this is just a sample, but Is it possible that I use list also un streamwriter?

If you want a one line solution (code golf :) ) you can use
string path = #"C:\Test.txt";
string lineToReplace = "Relpace This Line";
string newLineValue = "I Replaced This Line";
File.WriteAllLines(path, File.ReadAllLines(path).Select(line => line.Equals(lineToReplace) ? newLineValue : line));

You cannot just change a line as such but you can to ReadAllLines, find the line you want to change, change it and write all of it to the file again :
StringBuilder newFile = new StringBuilder();
string temp = "";
string[] file = File.ReadAllLines(#"txtfile");
foreach (string line in file)
{
if (line.Contains("string you want to replace"))
{
temp = line.Replace("string you want to replace", "New String");
newFile.Append(temp + "\r\n");
continue;
}
newFile.Append(line + "\r\n");
}
File.WriteAllText(#"txtfile", newFile.ToString());

Read the file into memory, changing the line(s) you want to change, close the reader, open the file for writing, write the new contents of the file out.

Edit a specific Line of a Text File in C#

I have two text files, Source.txt and Target.txt. The source will never be modified and contain N lines of text. So, I want to delete a specific line of text in Target.txt, and replace by an specific line of text from Source.txt, I know what number of line I need, actually is the line number 2, both files.
I haven something like this:
string line = string.Empty;
int line_number = 1;
int line_to_edit = 2;
using StreamReader reader = new StreamReader(#"C:\target.xml");
using StreamWriter writer = new StreamWriter(#"C:\target.xml");
while ((line = reader.ReadLine()) != null)
{
if (line_number == line_to_edit)
writer.WriteLine(line);
line_number++;
}
But when I open the Writer, the target file get erased, it writes the lines, but, when opened, the target file only contains the copied lines, the rest get lost.
What can I do?

the easiest way is :
static void lineChanger(string newText, string fileName, int line_to_edit)
{
string[] arrLine = File.ReadAllLines(fileName);
arrLine[line_to_edit - 1] = newText;
File.WriteAllLines(fileName, arrLine);
}
usage :
lineChanger("new content for this line" , "sample.text" , 34);

You can't rewrite a line without rewriting the entire file (unless the lines happen to be the same length). If your files are small then reading the entire target file into memory and then writing it out again might make sense. You can do that like this:
using System;
using System.IO;
class Program
{
static void Main(string[] args)
{
int line_to_edit = 2; // Warning: 1-based indexing!
string sourceFile = "source.txt";
string destinationFile = "target.txt";
// Read the appropriate line from the file.
string lineToWrite = null;
using (StreamReader reader = new StreamReader(sourceFile))
{
for (int i = 1; i <= line_to_edit; ++i)
lineToWrite = reader.ReadLine();
}
if (lineToWrite == null)
throw new InvalidDataException("Line does not exist in " + sourceFile);
// Read the old file.
string[] lines = File.ReadAllLines(destinationFile);
// Write the new file over the old file.
using (StreamWriter writer = new StreamWriter(destinationFile))
{
for (int currentLine = 1; currentLine <= lines.Length; ++currentLine)
{
if (currentLine == line_to_edit)
{
writer.WriteLine(lineToWrite);
}
else
{
writer.WriteLine(lines[currentLine - 1]);
}
}
}
}
}
If your files are large it would be better to create a new file so that you can read streaming from one file while you write to the other. This means that you don't need to have the whole file in memory at once. You can do that like this:
using System;
using System.IO;
class Program
{
static void Main(string[] args)
{
int line_to_edit = 2;
string sourceFile = "source.txt";
string destinationFile = "target.txt";
string tempFile = "target2.txt";
// Read the appropriate line from the file.
string lineToWrite = null;
using (StreamReader reader = new StreamReader(sourceFile))
{
for (int i = 1; i <= line_to_edit; ++i)
lineToWrite = reader.ReadLine();
}
if (lineToWrite == null)
throw new InvalidDataException("Line does not exist in " + sourceFile);
// Read from the target file and write to a new file.
int line_number = 1;
string line = null;
using (StreamReader reader = new StreamReader(destinationFile))
using (StreamWriter writer = new StreamWriter(tempFile))
{
while ((line = reader.ReadLine()) != null)
{
if (line_number == line_to_edit)
{
writer.WriteLine(lineToWrite);
}
else
{
writer.WriteLine(line);
}
line_number++;
}
}
// TODO: Delete the old file and replace it with the new file here.
}
}
You can afterwards move the file once you are sure that the write operation has succeeded (no excecption was thrown and the writer is closed).
Note that in both cases it is a bit confusing that you are using 1-based indexing for your line numbers. It might make more sense in your code to use 0-based indexing. You can have 1-based index in your user interface to your program if you wish, but convert it to a 0-indexed before sending it further.
Also, a disadvantage of directly overwriting the old file with the new file is that if it fails halfway through then you might permanently lose whatever data wasn't written. By writing to a third file first you only delete the original data after you are sure that you have another (corrected) copy of it, so you can recover the data if the computer crashes halfway through.
A final remark: I noticed that your files had an xml extension. You might want to consider if it makes more sense for you to use an XML parser to modify the contents of the files instead of replacing specific lines.

When you create a StreamWriter it always create a file from scratch, you will have to create a third file and copy from target and replace what you need, and then replace the old one.
But as I can see what you need is XML manipulation, you might want to use XmlDocument and modify your file using Xpath.

You need to Open the output file for write access rather than using a new StreamReader, which always overwrites the output file.
StreamWriter stm = null;
fi = new FileInfo(#"C:\target.xml");
if (fi.Exists)
stm = fi.OpenWrite();
Of course, you will still have to seek to the correct line in the output file, which will be hard since you can't read from it, so unless you already KNOW the byte offset to seek to, you probably really want read/write access.
FileStream stm = fi.Open(FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);
with this stream, you can read until you get to the point where you want to make changes, then write. Keep in mind that you are writing bytes, not lines, so to overwrite a line you will need to write the same number of characters as the line you want to change.

I guess the below should work (instead of the writer part from your example). I'm unfortunately with no build environment so It's from memory but I hope it helps
using (var fs = File.Open(filePath, FileMode.Open, FileAccess.ReadWrite)))
{
var destinationReader = StreamReader(fs);
var writer = StreamWriter(fs);
while ((line = reader.ReadLine()) != null)
{
if (line_number == line_to_edit)
{
writer.WriteLine(lineToWrite);
}
else
{
destinationReader .ReadLine();
}
line_number++;
}
}

The solution works fine. But I need to change single-line text when the same text is in multiple places. For this, need to define a trackText to start finding after that text and finally change oldText with newText.
private int FindLineNumber(string fileName, string trackText, string oldText, string newText)
{
int lineNumber = 0;
string[] textLine = System.IO.File.ReadAllLines(fileName);
for (int i = 0; i< textLine.Length;i++)
{
if (textLine[i].Contains(trackText)) //start finding matching text after.
traced = true;
if (traced)
if (textLine[i].Contains(oldText)) // Match text
{
textLine[i] = newText; // replace text with new one.
traced = false;
System.IO.File.WriteAllLines(fileName, textLine);
lineNumber = i;
break; //go out from loop
}
}
return lineNumber
}