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C# text file to string array and how to remove specific strings?

I need read a text file (10mb) and convert to .csv. See below portion of code:
string DirPathForm = System.IO.Path.GetDirectoryName(System.Reflection.Assembly.GetEntryAssembly().Location);'
string[] lines = File.ReadAllLines(DirPathForm + #"\file.txt");
Some portion of the text file have a pattern. So, used as below:
string[] lines1 = lines.Select(x => x.Replace("abc[", "ab,")).ToArray();
Array.Clear(lines, 0, lines.Length);
lines = lines1.Select(x => x.Replace("] CDE ", ",")).ToArray();
Some portion does not have a pattern to use directly Replace. The question is how remove the characters, numbers and whitespaces in this portion. Please see below?
string[] lines = {
"a] 773 b",
"e] 1597 t",
"z] 0 c"
};
to get the result below:
string[] result = {
"a,b",
"e,t",
"z,c"
};
obs: the items removed need be replaced by ",".

First of all, you should not use ReadAllLines since it is a huge file operation. It will load all the data into RAM and it is not correct. Instead, read the lines one by one in a loop.
Secondly, you can definitely use regex to replace data from the first condition to the second one.

How to add text to the line that starts with "hello" in a file

I have a file that contains many lines. There is a line here looking like below:
hello jim jack nina richi sam
I need to add a specific text salmon in this line and change it to below (it could be added anywhere in this line -end -begining - in the middle -doesnt matter ):
hello jim jack nina richi sam salmon
I tried:
string path = #"C:\testFolder\newTestLog.txt";
StreamReader myReader = new StreamReader(path);
string[] allLines = File.ReadAllLines(path);
foreach (string element in allLines) {
if (element.StartsWith("hello"))
{
Console.WriteLine(element);
}
}
myReader.Close();
}
Using this I'm able to read the file line by line and add each line to an array and print that line if that starts with "hello", but I'm not sure how to add text to this line

You should use what Joel answered it's nicer but if you're having trouble implementing it try this. After adding the salmon to the lines that start with hello you can overwrite the txt file by using File.WriteAllLines
string filePath = #"C:\testFolder\newTestLog.txt";
string[] allLines = File.ReadAllLines(filePath);
for(int i = 0; i < allLines.Length; i++)
{
if (allLines[i].StartsWith("hello"))
{
allLines[i] += " salmon";
}
}
File.WriteAllLines(filePath, allLines);

Try this:
string path = #"C:\testFolder\newTestLog.txt";
var lines = File.ReadLines(path).Select(l => l + l.StartsWith("hello")?" salmon":"");
foreach (string line in lines)
Console.WriteLine(line);
Note that this still only writes the results to the Console, as your sample does. It's not clear what you really want to happen with the output.
If you want this saved to the original file, you've opened up a small can of worms. Think of all of the data in your file as if it's stored in one contiguous block1. If you append text to any line in the file, that text has nowhere to go but to overwrite the beginning of the next. As a practical matter, if you need to modify file, this often means either writing out a whole new file, and then deleting/renaming when done, or alternatively keeping the whole file in memory and writing it all from start to finish.
Using the 2nd approach, where we keep everything in memory, you can do this:
string path = #"C:\testFolder\newTestLog.txt";
var lines = File.ReadAllLines(path).Select(l => l + l.StartsWith("hello")?" salmon":"");
File.WriteAllLines(path, lines);
1 In fact, a file may be split into several fragments on the disk, but even so, each fragment is presented to your program as part of a single whole.

Text file line by line into string array

I need help, trying to take a large text document ~1000 lines and put it into a string array, line by line.
Example:
string[] s = {firstLineHere, Secondline, etc};
I also want a way to find the first word, only the first word of the line, and once first word it found, copy the entire line. Find only the first word or each line!

You can accomplish this with File.ReadAllLines combined with a little Linq (to accomplish the addition to the question stated in the comments of Praveen's answer.
string[] identifiers = { /*Your identifiers for needed lines*/ };
string[] allLines = File.ReadAllLines("C:\test.txt");
string[] neededLines = allLines.Where(c => identifiers.Contains(c.SubString(0, c.IndexOf(' ') - 1))).ToArray();
Or make it more of a one liner:
string[] lines = File.ReadAllLines("your path").Where(c => identifiers.Contains(c.SubString(0, c.IndexOf(' ') - 1))).ToArray();
This will give you array of all the lines in your document that start with the keywords you define within your identifiers string array.

There is an inbuilt method to achieve your requirement.
string[] lines = System.IO.File.ReadAllLines(#"C:\sample.txt");
If you want to read the file line by line
List<string> lines = new List<string>();
using (StreamReader reader = new StreamReader(#"C:\sample.txt"))
{
while (reader.Peek() >= 0)
{
string line = reader.ReadLine();
//Add your conditional logic to add the line to an array
if (line.Contains(searchTerm)) {
lines.Add(line);
}
}
}

Another option you could use would be to read each individual line, while splitting the line into segments and comparing only the first element against
the provided search term. I have provided a complete working demonstration below:
Solution:
class Program
{
static void Main(string[] args)
{
// Get all lines that start with a given word from a file
var result = GetLinesWithWord("The", "temp.txt");
// Display the results.
foreach (var line in result)
{
Console.WriteLine(line + "\r");
}
Console.ReadLine();
}
public static List<string> GetLinesWithWord(string word, string filename)
{
List<string> result = new List<string>(); // A list of strings where the first word of each is the provided search term.
// Create a stream reader object to read a text file.
using (StreamReader reader = new StreamReader(filename))
{
string line = string.Empty; // Contains a single line returned by the stream reader object.
// While there are lines in the file, read a line into the line variable.
while ((line = reader.ReadLine()) != null)
{
// If the line is white space, then there are no words to compare against, so move to next line.
if (line != string.Empty)
{
// Split the line into parts by a white space delimiter.
var parts = line.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
// Get only the first word element of the line, trim off any additional white space
// and convert the it to lowercase. Compare the word element to the search term provided.
// If they are the same, add the line to the results list.
if (parts.Length > 0)
{
if (parts[0].ToLower().Trim() == word.ToLower().Trim())
{
result.Add(line);
}
}
}
}
}
return result;
}
}
Where the sample text file may contain:
How shall I know thee in the sphere which keeps
The disembodied spirits of the dead,
When all of thee that time could wither sleeps
And perishes among the dust we tread?
For I shall feel the sting of ceaseless pain
If there I meet thy gentle presence not;
Nor hear the voice I love, nor read again
In thy serenest eyes the tender thought.
Will not thy own meek heart demand me there?
That heart whose fondest throbs to me were given?
My name on earth was ever in thy prayer,
Shall it be banished from thy tongue in heaven?
In meadows fanned by heaven's life-breathing wind,
In the resplendence of that glorious sphere,
And larger movements of the unfettered mind,
Wilt thou forget the love that joined us here?
The love that lived through all the stormy past,
And meekly with my harsher nature bore,
And deeper grew, and tenderer to the last,
Shall it expire with life, and be no more?
A happier lot than mine, and larger light,
Await thee there; for thou hast bowed thy will
In cheerful homage to the rule of right,
And lovest all, and renderest good for ill.
For me, the sordid cares in which I dwell,
Shrink and consume my heart, as heat the scroll;
And wrath has left its scar--that fire of hell
Has left its frightful scar upon my soul.
Yet though thou wear'st the glory of the sky,
Wilt thou not keep the same beloved name,
The same fair thoughtful brow, and gentle eye,
Lovelier in heaven's sweet climate, yet the same?
Shalt thou not teach me, in that calmer home,
The wisdom that I learned so ill in this--
The wisdom which is love--till I become
Thy fit companion in that land of bliss?
And you wanted to retrieve every line where the first word of the line is the word 'the' by calling the method like so:
var result = GetLinesWithWord("The", "temp.txt");
Your result should then be the following:
The disembodied spirits of the dead,
The love that lived through all the stormy past,
The same fair thoughtful brow, and gentle eye,
The wisdom that I learned so ill in this--
The wisdom which is love--till I become
Hopefully this answers your question adequately enough.

Alternative to File.AppendAllText for newline

I am trying to read characters from a file and then append them in another file after removing the comments (which are followed by semicolon).
sample data from parent file:
Name- Harly Brown ;Name is Harley Brown
Age- 20 ;Age is 20 years
Desired result:
Name- Harley Brown
Age- 20
I am trying the following code-
StreamReader infile = new StreamReader(floc + "G" + line + ".NC0");
while (infile.Peek() != -1)
{
letter = Convert.ToChar(infile.Read());
if (letter == ';')
{
infile.ReadLine();
}
else
{
System.IO.File.AppendAllText(path, Convert.ToString(letter));
}
}
But the output i am getting is-
Name- Harley Brown Age-20
Its because AppendAllText is not working for the newline. Is there any alternative?

Sure, why not use File.AppendAllLines. See documentation here.
Appends lines to a file, and then closes the file. If the specified file does not exist, this method creates a file, writes the specified lines to the file, and then closes the file.
It takes in any IEnumerable<string> and adds every line to the specified file. So it always adds the line on a new line.
Small example:
const string originalFile = #"D:\Temp\file.txt";
const string newFile = #"D:\Temp\newFile.txt";
// Retrieve all lines from the file.
string[] linesFromFile = File.ReadAllLines(originalFile);
List<string> linesToAppend = new List<string>();
foreach (string line in linesFromFile)
{
// 1. Split the line at the semicolon.
// 2. Take the first index, because the first part is your required result.
// 3. Trim the trailing and leading spaces.
string appendAbleLine = line.Split(';').FirstOrDefault().Trim();
// Add the line to the list of lines to append.
linesToAppend.Add(appendAbleLine);
}
// Append all lines to the file.
File.AppendAllLines(newFile, linesToAppend);
Output:
Name- Harley Brown
Age- 20
You could even change the foreach-loop into a LINQ-expression, if you prefer LINQ:
List<string> linesToAppend = linesFromFile.Select(line => line.Split(';').FirstOrDefault().Trim()).ToList();

Why use char by char comparison when .NET Framework is full of useful string manipulation functions?
Also, don't use a file write function multiple times when you can use it only one time, it's time and resources consuming!
StreamReader stream = new StreamReader("file1.txt");
string str = "";
while ((string line = infile.ReadLine()) != null) { // Get every line of the file.
line = line.Split(';')[0].Trim(); // Remove comment (right part of ;) and useless white characters.
str += line + "\n"; // Add it to our final file contents.
}
File.WriteAllText("file2.txt", str); // Write it to the new file.

You could do this with LINQ, System.File.ReadLines(string), and System.File.WriteAllLines(string, IEnumerable<string>). You could also use System.File.AppendAllLines(string, IEnumerable<string>) in a find-and-replace fashion if that was, in fact, the functionality you were going for. The difference, as the names suggest, is whether it writes everything out as a new file or if it just appends to an existing one.
System.IO.File.WriteAllLines(newPath, System.IO.File.ReadLines(oldPath).Select(c =>
{
int semicolon = c.IndexOf(';');
if (semicolon > -1)
return c.Remove(semicolon);
else
return c;
}));
In case you aren't super familiar with LINQ syntax, the idea here is to loop through each line in the file, and if it contains a semicolon (that is, IndexOf returns something that is over -1) we cut that off, and otherwise, we just return the string. Then we write all of those to the file. The StreamReader equivalent to this would be:
using (StreamReader reader = new StreamReader(oldPath))
using (StreamWriter writer = new StreamWriter(newPath))
{
string line;
while ((line = reader.ReadLine()) != null)
{
int semicolon = line.IndexOf(';');
if (semicolon > -1)
line = c.Remove(semicolon);
writer.WriteLine(line);
}
}
Although, of course, this would feed an extra empty line at the end and the LINQ version wouldn't (as far as I know, it occurs to me that I'm not one hundred percent sure on that, but if someone reading this does know I would appreciate a comment).
Another important thing to note, just looking at your original file, you might want to add in some Trim calls, since it looks like you can have spaces before your semicolons, and I don't imagine you want those copied through.

Parsing a textfile in C# with skipping some contents

I'm trying to parse a text file that has a heading and the body. In the heading of this file, there are line number references to sections of the body. For example:
SECTION_A 256
SECTION_B 344
SECTION_C 556
This means, that SECTION_A starts in line 256.
What would be the best way to parse this heading into a dictionary and then when necessary read the sections.
Typical scenarios would be:
Parse the header and read only section SECTION_B
Parse the header and read fist paragraph of each section.
The data file is quite large and I definitely don't want to load all of it to the memory and then operate on it.
I'd appreciate your suggestions. My environment is VS 2008 and C# 3.5 SP1.

You can do this quite easily.
There are three parts to the problem.
1) How to find where a line in the file starts. The only way to do this is to read the lines from the file, keeping a list that records the start position in the file of that line. e.g
List lineMap = new List();
lineMap.Add(0); // Line 0 starts at location 0 in the data file (just a dummy entry)
lineMap.Add(0); // Line 1 starts at location 0 in the data file
using (StreamReader sr = new StreamReader("DataFile.txt"))
{
String line;
int lineNumber = 1;
while ((line = sr.ReadLine()) != null)
lineMap.Add(sr.BaseStream.Position);
}
2) Read and parse your index file into a dictionary.
Dictionary index = new Dictionary();
using (StreamReader sr = new StreamReader("IndexFile.txt"))
{
String line;
while ((line = sr.ReadLine()) != null)
{
string[] parts = line.Split(' '); // Break the line into the name & line number
index.Add(parts[0], Convert.ToInt32(parts[1]));
}
}
Then to find a line in your file, use:
int lineNumber = index["SECTION_B";]; // Convert section name into the line number
long offsetInDataFile = lineMap[lineNumber]; // Convert line number into file offset
Then open a new FileStream on DataFile.txt, Seek(offsetInDataFile, SeekOrigin.Begin) to move to the start of the line, and use a StreamReader (as above) to read line(s) from it.

Well, obviously you can store the name + line number into a dictionary, but that's not going to do you any good.
Well, sure, it will allow you to know which line to start reading from, but the problem is, where in the file is that line? The only way to know is to start from the beginning and start counting.
The best way would be to write a wrapper that decodes the text contents (if you have encoding issues) and can give you a line number to byte position type of mapping, then you could take that line number, 256, and look in a dictionary to know that line 256 starts at position 10000 in the file, and start reading from there.
Is this a one-off processing situation? If not, have you considered stuffing the entire file into a local database, like a SQLite database? That would allow you to have a direct mapping between line number and its contents. Of course, that file would be even bigger than your original file, and you'd need to copy data from the text file to the database, so there's some overhead either way.

Just read the file one line at a time and ignore the data until you get to the ones you need. You won't have any memory issues, but performance probably won't be great. You can do this easily in a background thread though.

Read the file until the end of the header, assuming you know where that is. Split the strings you've stored on whitespace, like so:
Dictionary<string, int> sectionIndex = new Dictionary<string, int>();
List<string> headers = new List<string>(); // fill these with readline
foreach(string header in headers) {
var s = header.Split(new[]{' '});
sectionIndex.Add(s[0], Int32.Parse(s[1]));
}
Find the dictionary entry you want, keep a count of the number of lines read in the file, and loop until you hit that line number, then read until you reach the next section's starting line. I don't know if you can guarantee the order of keys in the Dictionary, so you'd probably need the current and next section's names.
Be sure to do some error checking to make sure the section you're reading to isn't before the section you're reading from, and any other error cases you can think of.

You could read line by line until all the heading information is captured and stop (assuming all section pointers are in the heading). You would have the section and line numbers for use in retrieving the data at a later time.
string dataRow = "";
try
{
TextReader tr = new StreamReader("filename.txt");
while (true)
{
dataRow = tr.ReadLine();
if (dataRow.Substring(1, 8) != "SECTION_")
break;
else
//Parse line for section code and line number and log values
continue;
}
tr.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
}