Develop Reference

C# - Foreach two line in Text File

I am developing in C#.
I have a text file containing the following:
Sam
NYC
Mii
Peru
LEO
Argentina
I want to iterate through this file two line by two line, then print to the console the first line, second line (the Name and the Country) of each couple, so the output would be:
Sam, NYC
Mii, Peru
Here is what I have tried:
int linenum = 0;
foreach (string line in File.ReadLines("c:\\file.txt"))
{
string word = line;
string s = "";
string j = "";
linenum = linenum + 1;
if(linenum % 2 != 0) //impaire
{
s = line;
}
else
{
j = line;
}
Console.WriteLine((string.Concat(s, j));
}
But that's not working, I want to do:
int linenum = 0;
foreach( two lines in File.ReadLines("c:\\file.txt"))
{
linenum = linenum + 1;
//get the first line (linenum = 1) and store it in a string s
// then get the second line (linenum = 2) and store it in a string j
// then print the two strings together to the console like that
Console.WriteLine((string.Concat("S: " + s,"J: " j));
}
How can I do that ?

Use File.ReadAllLines to return an array of strings:
var lines = File.ReadAllLines(filePath);
for (int i = 0; i < lines.Length; i+=2)
{
var s = lines[i];
var j = lines[i+1];
Console.WriteLine($"S: {s} J: {s}");
}

You do your output with Console.WriteLine in every line, but you also should do that only for every second line. Furthermore, your variables s and j live inside the loop's scope, so they are recreated with every iteration and loose their prior value.
int i = 0; string prev = "";
foreach (string line in File.ReadLines("c:\\file.txt")) {
if (i++ % 2 == 0) prev = line;
else Console.WriteLine($"{prev}, {line}");
}
Another approach would be iterating the array you get from File.ReadAllLines with an for loop instead of foreach and increase the index by 2
var lines = File.ReadAllLines("c:\\file.txt");
//make sure, you have an even number of lines!
if (lines.Length% 2 == 0) for (int i = 0; i < lines.Length; i+=2) {
Console.WriteLine($"{lines[i]}, {lines[i+1]}");
}

You can write yourself a little helper method to return batches of lines.
This implementation handles files that are not a multiple of the batch size (2 in your case) by returning "" for the missing lines at the end of the file.
public static IEnumerable<string[]> BatchedLinesFromFile(string filename, int batchSize)
{
string[] result = Enumerable.Repeat("", batchSize).ToArray();
int count = 0;
foreach (var line in File.ReadLines(filename))
{
result[count++] = line;
if (count != batchSize)
continue;
yield return result;
count = 0;
result = Enumerable.Repeat("", batchSize).ToArray();
}
if (count > 0)
yield return result;
}
Note that this also returns a separate array for each result, in case you make a copy of it.
Given that code, you can use it like so:
foreach (var batch in BatchedLinesFromFile(filename, 2))
{
Console.WriteLine(string.Join(", ", batch));
}

Actually, you can use LINQ to get two lines in a time using Take
var twoLines = File.ReadLines(#"YourPath").Take(2));
As you can use Skip to skip the two lines you took and take the next two lines like :
var twoLines = File.ReadLines(#"YourPath").Skip(2).Take(2));
EDIT : Thanks for #derpirscher there were a performance issue so changed the code to the following :
first read the whole file and store it in a string array
then loop through it using LINQ to take two elements from the array in a time.
string[] myStringArray = File.ReadAllLines(#"YourFile.txt");
for (int i = 0; i < myStringArray.Length ; i+=2)
{
var twoLines = myStringArray.Skip(i).Take(2).ToArray();
}

Another one, using Enumerable.Repeat() and an interger selector incremented a [NumberOfLines / 2] times.
Could be interesting for the LINQ addicted (a for / foreach solution is probably better anyway).
string[] input = File.ReadAllLines([SourcePath]);
int Selector = -1;
string[] output = Enumerable.Repeat(0, input.Length / 2).Select(_ => {
Selector += 2;
return $"{input[Selector - 1]} {input[Selector]}";
}).ToArray();
The output is:
Sam NYC
Mii Peru
LEO Argentina

Use the right tool for the job. foreach() is not the right tool here.
Without giving up the memory efficiency of ReadLines() over ReadAll():
using (var lines = File.ReadLines("c:\\file.txt").GetEnumerator())
{
while (lines.MoveNext())
{
string firstLine = lines.Current;
if (!lines.MoveNext())
throw new InvalidOperationException("odd nr of lines");
string secondLine = lines.Current;
// use 2 lines
Console.WriteLine("S: " + firstLine ,"J: " + secondLine);
}
}

split string in to several strings at specific points

I have a text file with lines of text laid out like so
12345MLOL68
12345MLOL68
12345MLOL68
I want to read the file and add commas to the 5th point, 6th point and 9th point and write it to a different text file so the result would be.
12345,M,LOL,68
12345,M,LOL,68
12345,M,LOL,68
This is what I have so far
public static void ToCSV(string fileWRITE, string fileREAD)
{
int count = 0;
string x = "";
StreamWriter commas = new StreamWriter(fileWRITE);
string FileText = new System.IO.StreamReader(fileREAD).ReadToEnd();
var dataList = new List<string>();
IEnumerable<string> splitString = Regex.Split(FileText, "(.{1}.{5})").Where(s => s != String.Empty);
foreach (string y in splitString)
{
dataList.Add(y);
}
foreach (string y in dataList)
{
x = (x + y + ",");
count++;
if (count == 3)
{
x = (x + "NULL,NULL,NULL,NULL");
commas.WriteLine(x);
x = "";
count = 0;
)
}
commas.Close();
}
The problem I'm having is trying to figure out how to split the original string lines I read in at several points. The line
IEnumerable<string> splitString = Regex.Split(FileText, "(.{1}.{5})").Where(s => s != String.Empty);
Is not working in the way I want to. It's just adding up the 1 and 5 and splitting all strings at the 6th char.
Can anyone help me split each string at specific points?

Simpler code:
public static void ToCSV(string fileWRITE, string fileREAD)
{
string[] lines = File.ReadAllLines(fileREAD);
string[] splitLines = lines.Select(s => Regex.Replace(s, "(.{5})(.)(.{3})(.*)", "$1,$2,$3,$4")).ToArray();
File.WriteAllLines(fileWRITE, splitLines);
}

Just insert at the right place in descending order like this.
string str = "12345MLOL68";
int[] indices = {5, 6, 9};
indices = indices.OrderByDescending(x => x).ToArray();
foreach (var index in indices)
{
str = str.Insert(index, ",");
}
We're doing this in descending order because if we do other way indices will change, it will be hard to track it.
Here is the Demo

Why don't you use substring , example
editedstring=input.substring(0,5)+","+input.substring(5,1)+","+input.substring(6,3)+","+input.substring(9);
This should suits your need.

How can I read X lines down from another line in a text file?

I have a text file that I load into a string array. The contents of the file looks something like this:
OTI*IA*IX*NA~ REF*G1*J EVERETTE~ REF*11*0113722462~
AMT*GW*229.8~ NM1*QC*1*JENNINGS*PHILLIP~ OTI*IA*IX*NA~ REF*G1*J
EVERETTE~ REF*11*0113722463~ AMT*GW*127.75~
NM1*QC*1*JENNINGS*PHILLIP~ OTI*IA*IX*NA~ REF*G1*J EVERETTE~
REF*11*0113722462~ AMT*GW*10.99~ NM1*QC*1*JENNINGS*PHILLIP~ ...
I'm looking for the lines that start with OTI, and if it's followed by "IA" then I need to get the 10 digit number from the line that starts with REF*11. So far, I have this:
string[] readText = File.ReadAllLines("myfile.txt");
foreach (string s in readText) //string contains 1 line of text from above example
{
string[] currentline = s.Split('*');
if (currentline[0] == "OTI")
{
//move down 2 lines and grab the 10 digit
//number from the line that starts with REF*11
}
}
The line I need is always 2 lines after the current OTI line. How do I access the line that's 2 lines down from my current line?

Instead of using foreach() you can use a for(int index = 0; index < readText.Length; index++)
Then you know the line you are accessing and you can easily say int otherIndex = index + 2
string[] readText = File.ReadAllLines("myfile.txt");
for(int index = 0; index < readText.Length; index++)
{
string[] currentline = readText[index].Split('*');
if (currentline[0] == "OTI")
{
//move down 2 lines and grab the 10 digit
//number from the line that starts with REF*11
int refIndex = index + 2;
string refLine = readText[refIndex];
}
}

What about:
string[] readText = File.ReadAllLines("myfile.txt");
for (int i = 0; i < readText.Length; i++)
{
if (readText[i].StartsWith("OTI") && readText[i+2].StartsWith("REF*11")){
string number = readText[i+2].Substring("REF*11".Length, 10);
//do something
}
}

This looks like an EDI file! Ahh, EDI, the memories...
The good news is that the EDI file is delimited, just like most CSV file formats. You can use any standard CSV file library to load the EDI file into a gigantic array, and then iterate through it by position.
I published my open source CSV library here, feel free to use it if it's helpful. You can simply specify the "asterisk" as the delimiter:
https://code.google.com/p/csharp-csv-reader/
// This code assumes the file is on disk, and the first row of the file
// has the names of the columns on it
DataTable dt = CSVReader.LoadDataTable(myfilename, '*', '\"');
At this point, you can iterate through the datatable as normal.
for (int i = 0; i < dt.Rows.Count; i++) {
if (dt.Rows[i][0] == "OTI") {
Console.WriteLine("The row I want is: " + dt.Rows[i + 2][0]);
}
}

If you want to use regex to tokenize the items and create dynamic entities, here is such a pattern
string data = #"NM1*QC*1*JENNINGS*PHILLIP~
OTI*IA*IX*NA~
REF*G1*J EVERETTE~
REF*11*0113722463~
AMT*GW*127.75~
NM1*QC*1*JENNINGS*PHILLIP~
OTI*IA*IX*NA~
REF*G1*J EVERETTE~
REF*11*0113722462~
AMT*GW*10.99~
NM1*QC*1*JENNINGS*PHILLIP~";
string pattern = #"^(?<Command>\w{3})((?:\*)(?<Value>[^~*]+))+";
var lines = Regex.Matches(data, pattern, RegexOptions.Multiline)
.OfType<Match>()
.Select (mt => new
{
Op = mt.Groups["Command"].Value,
Data = mt.Groups["Value"].Captures.OfType<Capture>().Select (c => c.Value)
}
);
That produces a list of items like this which you can apply your business logic to:

Why dont you use regular expression matches using Regex.Match or Regex.Matches defined in System.Text.RegularExpressions? You can also look at string pattern matching algorithms such as the Knuth-Morris-Pratt algorithms.

string[] readText = File.ReadAllLines("myfile.txt");
foreach (string s in readText) //string contains 1 line of text from above example
{
string[] currentline = s.Split('*');
if (currentline[0] == "REF"&&currentline[1] == "11")
{
found=false;
needed=current+2;
}
}

string[] readText = File.ReadAllLines("myfile.txt");
for(int linenum = 0;linenum < readText.Length; linenum++)
{
string s = readText[linenum];
string[] currentline = s.Split('*');
if (currentline[0] == "OTI")
{
//move down 2 lines and grab the 10 digit
linenum +=2;
string refLine = readText[linenum];
//number from the line that starts with REF*11
// Extract your number here from refline
}
}

Thank guys .. this is what I came up with, but I'm also reading your answers as I KNOW I will learn something! Thanks again!
string[] readText = File.ReadAllLines("myfile.txt");
int i = 0;
foreach (string s in readText)
{
string[] currentline = s.Split('*');
if (currentline[0] == "OTI")
{
lbRecon.Items.Add(readText[i+2].Substring(8, 9));
}
i++;
}

out of bounds error c#

Im trying to read contents of a csv file into different variables in order to send to a web service.It has been working fine but suddenly today i got and exception.
index was outside the bounds of the array:
what Did I do wrong?
String sourceDir = #"\\198.0.0.4\e$\Globus\LIVE\bnk.run\URA.BP\WEBOUT\";
// Process the list of files found in the directory.
string[] fileEntries = Directory.GetFiles(sourceDir);
foreach (string fileName2 in fileEntries)
{
// read values
StreamReader st = new StreamReader(fileName2);
while (st.Peek() >= 0)
{
String report1 = st.ReadLine();
String[] columns = report1.Split(','); //split columns
String prnout = columns[0];
String tinout = columns[1];
String amtout = columns[2];
String valdate = columns[3];
String paydate = columns[4];
String status = columns[5];
String branch = columns[6];
String reference = columns[7];
}
}

It's hard to guess without even seeing the .csv file, but my first one would be that you don't have 8 columns.
It would be easier if you could show the original .csv file, and tell us where the exception pops.
edit: If you think the data is alright, I'd suggest you debugging and see what the split call returns in Visual Studio. That might help
edit2: And since you're doing that processing in a loop, make sure each row has at least 8 columns.

My money is on bad data file. If that is the only thing in the equation that has changed (aka you haven't made any code changes) then that's pretty much your only option.
If your data file isn't too long post it here and we can tell you for sure.
You can add something like below to check for invalid column lengths:
while (st.Peek() >= 0)
{
String report1 = st.ReadLine();
String[] columns = report1.Split(','); //split columns
if(columns.Length < 8)
{
//Log something useful, throw an exception, whatever.
//You have the option to quitely note that there was a problem and
//continue on processing the rest of the file if you want.
continue;
}
//working with columns below
}

Just for sanity's sake, I combined all the various notes written here. This code is a bit cleaner and has some validation in it.
Try this:
string dir = #"\\198.0.0.4\e$\Globus\LIVE\bnk.run\URA.BP\WEBOUT\";
foreach (string fileName2 in Directory.GetFiles(dir)) {
StreamReader st = new StreamReader(fileName2);
while (!sr.EndOfStream) {
string line = sr.ReadLine();
if (!String.IsNullOrEmpty(line)) {
string[] columns = line.Split(',');
if (columns.Length == 8) {
string prnout = columns[0];
string tinout = columns[1];
string amtout = columns[2];
string valdate = columns[3];
string paydate = columns[4];
string status = columns[5];
string branch = columns[6];
string reference = columns[7];
}
}
}
}
EDIT: As some other users have commented, the CSV format also accepts text qualifiers, which usually means the double quote symbol ("). For example, a text qualified line may look like this:
user,"Hello!",123.23,"$123,123.12",and so on,
Writing CSV parsing code is a little more complicated when you have a fully formatted file like this. Over the years I've been parsing improperly formatted CSV files, I've worked up a standard code script that passes virtually all unit tests, but it's a pain to explain.
/// <summary>
/// Read in a line of text, and use the Add() function to add these items to the current CSV structure
/// </summary>
/// <param name="s"></param>
public static bool TryParseLine(string s, char delimiter, char text_qualifier, out string[] array)
{
bool success = true;
List<string> list = new List<string>();
StringBuilder work = new StringBuilder();
for (int i = 0; i < s.Length; i++) {
char c = s[i];
// If we are starting a new field, is this field text qualified?
if ((c == text_qualifier) && (work.Length == 0)) {
int p2;
while (true) {
p2 = s.IndexOf(text_qualifier, i + 1);
// for some reason, this text qualifier is broken
if (p2 < 0) {
work.Append(s.Substring(i + 1));
i = s.Length;
success = false;
break;
}
// Append this qualified string
work.Append(s.Substring(i + 1, p2 - i - 1));
i = p2;
// If this is a double quote, keep going!
if (((p2 + 1) < s.Length) && (s[p2 + 1] == text_qualifier)) {
work.Append(text_qualifier);
i++;
// otherwise, this is a single qualifier, we're done
} else {
break;
}
}
// Does this start a new field?
} else if (c == delimiter) {
list.Add(work.ToString());
work.Length = 0;
// Test for special case: when the user has written a casual comma, space, and text qualifier, skip the space
// Checks if the second parameter of the if statement will pass through successfully
// e.g. "bob", "mary", "bill"
if (i + 2 <= s.Length - 1) {
if (s[i + 1].Equals(' ') && s[i + 2].Equals(text_qualifier)) {
i++;
}
}
} else {
work.Append(c);
}
}
list.Add(work.ToString());
// If we have nothing in the list, and it's possible that this might be a tab delimited list, try that before giving up
if (list.Count == 1 && delimiter != DEFAULT_TAB_DELIMITER) {
string[] tab_delimited_array = ParseLine(s, DEFAULT_TAB_DELIMITER, DEFAULT_QUALIFIER);
if (tab_delimited_array.Length > list.Count) {
array = tab_delimited_array;
return success;
}
}
// Return the array we parsed
array = list.ToArray();
return success;
}
You should note that, even as complicated as this algorithm is, it still is unable to parse CSV files where there are embedded newlines within a text qualified value, for example, this:
123,"Hi, I am a CSV File!
I am saying hello to you!
But I also have embedded newlines in my text.",2012-07-23
To solve those, I have a multiline parser that uses the Try() feature to add additional lines of text to verify that the main function worked correctly:
/// <summary>
/// Parse a line whose values may include newline symbols or CR/LF
/// </summary>
/// <param name="sr"></param>
/// <returns></returns>
public static string[] ParseMultiLine(StreamReader sr, char delimiter, char text_qualifier)
{
StringBuilder sb = new StringBuilder();
string[] array = null;
while (!sr.EndOfStream) {
// Read in a line
sb.Append(sr.ReadLine());
// Does it parse?
string s = sb.ToString();
if (TryParseLine(s, delimiter, text_qualifier, out array)) {
return array;
}
}
// Fails to parse - return the best array we were able to get
return array;
}

Since you don't know how many columns will be in csv file, you might need to test for length:
if (columns.Length == 8) {
String prnout = columns[0];
String tinout = columns[1];
...
}
I bet you just got an empty line (extra EOL at the end), and that's as simple as that

C# - Read/Copy/Replace Lines In Text

I have a text file that I am opening up and it is in a similar format to this:
10 SOME TEXT
20 T A40
B B5, C45, D48
30 B E25
40 B F17, G18
60 T H20, I23,
B J6, K7, L8, M9, N10, O11, P12,
Q31, R32, S33, T34, U35, V36,
W37, X38, Y39
100 T Z65
360 B A1, B4, C5, D6, E7, F10
2000 T SOME TEXT
423 TEXT
With this text I need to be able to read it and replace values accordingly. If a ReadLine begins with a number (ie, 10, 20, 30, 40, 60, 100, 360, 2000, 423) I need to to check if there is a T, B, or text after it. The only case that I need to change/reformat the lines when they come in and output them differently.
Example: 10 is fine except for I would like to add zeros in front of every number to make them 4 digits long (ie, 10 turns to 0010, 360 turns to 0360, 2000 stays the same). When the string "B B5, C45, D48" is read (this is the third line in the text) I need to change it to say "20A B5, C45, D48". I need to grab the number above the "B" and concat it to the "B" and replace the "B" with an "A". If instead of a "B" there is a "T" I simply need to remove the "T". Also, if a line does not start with a number or a "B" (ie, Q31 or W37) I need to concat that line with the previous line.
So after the changes take place it should look like this:
0010 SOME TEXT
0020 A40
0020A B5, C45, D48
0030A E25
0040A F17, G18
0060 H20, I23,
0060A J6, K7, L8, M9, N10, O11, P12, Q31, R32, S33, T34, U35, V36, W37, X38, Y39
0100 Z65
0360A A1, B4, C5, D6, E7, F10
2000 SOME TEXT
0423 TEXT
I am currently trying to use Regex to do this but I have been told that there is an easier way to do this and I am not sure how. So far I have been able to add the zeros in front of the numbers. Also, my code is adding an "A" to the end of everything as well as keeping the original number on the next line and I am not grabbing the lines that begin with anything but a digit.
This is what my current output is turning out to look like:
0010A
0010
0020A
0020
0030A
0030
0060A
0060
0100A
0100
0360A
0360
2000
2000
0423A
0423
I am obviously doing something wrong using Regex.
Here is my current code:
private void openRefsButton_Click(object sender, EventArgs e)
{
// Initialize the OpenFileDialog to specify the .txt extension as well as
// its intial directory for the file.
openRefs.DefaultExt = "*.txt";
openRefs.Filter = ".txt Files|*.txt";
openRefs.InitialDirectory = "C:\\";
openRefs.RestoreDirectory = true;
try
{
// Open the contents of the file into the originalTextRichTextBox.
if (openRefs.ShowDialog() == DialogResult.OK && openRefs.FileName.Length > 0)
refsTextRichTextBox.LoadFile(openRefs.FileName, RichTextBoxStreamType.PlainText);
// Throws a FileNotFoundException otherwise.
else
throw new FileNotFoundException();
StreamReader refsInput = File.OpenText(openRefs.FileName);
string regExpression = #"^[\d]+";
string findNewBottomRegex = #"^B\s";
StringBuilder buildNumberText = new StringBuilder();
StringBuilder formatMatchText = new StringBuilder();
foreach (string allLines in File.ReadAllLines(openRefs.FileName))
{
Match newBottomMatch = Regex.Match(allLines, findNewBottomRegex);
Match numberStartMatch = Regex.Match(allLines, regExpression);
int counter = 0;
if (counter < numberStartMatch.Length)
{
if (numberStartMatch.Value.Length == 2)
{
if (refsTextRichTextBox.Text.Contains(newBottomMatch.ToString()))
{
finalTextRichTextBox.AppendText("00" + numberStartMatch + "A\n");
}
finalTextRichTextBox.AppendText("00" + numberStartMatch + "\n");
}
else if (numberStartMatch.Value.Length == 3)
{
if (refsTextRichTextBox.Text.Contains(newBottomMatch.ToString()))
{
finalTextRichTextBox.AppendText("0" + numberStartMatch + "A\n");
}
finalTextRichTextBox.AppendText("0" + numberStartMatch + "\n");
}
else
{
if (refsTextRichTextBox.Text.Contains(newBottomMatch.ToString()))
{
finalTextRichTextBox.AppendText(numberStartMatch + "A\n");
}
finalTextRichTextBox.AppendText(numberStartMatch + "\n");
}
counter++;
}
}
}
// Catches an exception if the file was not opened.
catch (Exception)
{
MessageBox.Show("There was not a specified file path.", "Path Not Found Error",
MessageBoxButtons.OK, MessageBoxIcon.Warning);
}
}
}
}
QUESTION(S):
What is a better way to go about doing this task?
Are there any recommendations on changing my code to be more efficient and cleaner?
How do I properly split each line into number, T/B, A40 when every line is not the same?
After the lines are properly split, how do I replace copy the line before if the current line begins with a "B"?
If the line begins with "Q31" or similar, how do I add that current line to the end of the previous one?
Once this happens, is there a way to concat everything to create the speficied format above?
WORK FLOW #jaywayco
Open Text File
Read file line by line
Save each line in a list of strings
Split each string by ' '
Find each line that starts with a digit
Replace that digit to make it 4 digits in length
Check the following text after the digit to see if it is a "B ", "T ", or "SOME TEXT"
if "B " copy the line above
Add an "A" to the end of the digit
if "T " remove the "T "
if "SOME TEXT" do nothing
Find each line that starts with a "B "
Copy the digits on the line above and concat to the front of the "B "
Follow step 4.b.i
Find each line that starts with (or similar to) "Q31"
Concat this line to the end of the previous line
...?

Here's a really lame, procedural solution:
using System.IO;
using System.Collections.Generic;
namespace ConsoleApplication
{
class Program
{
static void Main(string[] args)
{
var list = new List<string>();
using (var reader = File.OpenText(#"c:\input.txt"))
{
while (true)
{
var line = reader.ReadLine();
if (string.IsNullOrEmpty(line)) break;
list.Add(line);
}
}
list = HandleRemoveTRequirement(list);
list = HandleFourDigitRequirement(list);
list = HandleConcatRequirement(list);
list = HandleStartsWithBRequirement(list);
list = HandleSecondElementIsBRequirement(list);
using (var output = new StreamWriter(#"c:\output.txt"))
{
foreach (var line in list)
{
output.WriteLine(line);
}
}
}
static List<string> HandleSecondElementIsBRequirement(List<string> list)
{
var result = new List<string>();
foreach (var line in list)
{
var parts = line.Split(' ');
if (parts[1].Equals("B"))
{
parts[0] += "A";
parts[1] = string.Empty;
result.Add(string.Join(" ", parts).Replace(" ", " "));
}
else
{
result.Add(line);
}
}
return result;
}
static List<string> HandleStartsWithBRequirement(List<string> list)
{
var result = new List<string>();
var i = 0;
foreach (var line in list)
{
var parts = line.Split(' ');
if (parts[0].Equals("B"))
{
parts[0] = string.Empty;
result.Add(list[i - 1].Split(' ')[0] + "A" + string.Join(" ", parts));
}
else
{
result.Add(line);
}
i++;
}
return result;
}
static List<string> HandleConcatRequirement(List<string> list)
{
var result = new List<string>();
foreach (var line in list)
{
var parts = line.Split(' ');
int test;
if (int.TryParse(parts[0], out test) || parts[0].Equals("B"))
{
result.Add(line);
}
else
{
result[result.Count -1] += line;
}
}
return result;
}
static List<string> HandleRemoveTRequirement(List<string> list)
{
var result = new List<string>();
foreach (var line in list)
{
var parts = line.Split(' ');
if (parts[1].Equals("T"))
{
parts[1] = string.Empty;
}
result.Add(string.Join(" ", parts).Replace(" ", " "));
}
return result;
}
static List<string> HandleFourDigitRequirement(List<string> list)
{
var result = new List<string>();
foreach (var line in list)
{
var parts = line.Split(' ');
int test;
if (int.TryParse(parts[0], out test))
{
parts[0] = parts[0].PadLeft(4, '0');
result.Add(string.Join(" ", parts));
}
else
{
result.Add(line);
}
}
return result;
}
}
}

These are pretty complicated requirements and I would be tempted to implement this as a workflow. This way you can separate out each of the logical steps and this will increase maintainability.
I would be tempted to represent the text file as an array of string arrays or even a data table. Then you can write general functions that concatenate/transform specific values

One way to possibly approach this is similiar to jaywayco's.
I'd start with placing each line split by spaces into it's own array. Place that array into an Array of arrays. From there you can consider your workflow. Your line array that is split by the spaces you can determine how to print it based off the first value, being a number or letter B etc... If it's a B, you know that it should start with array[i-1] first value, which would be the number etc. You'd have to think through the logic a bit, but I think you can understand where I am coming from. I'm not sure if this is the best approach or not, but I think this is the way I would tackle it. Good luck!
Edit: Here is some mock code...
var mainArray = new Array[textFile.Count];
//obviously get the count of number of lines set that to the size of your array object.
for(int i=0; i < mainArray.Length; i++)
{
var line = methodToGetLineFromTextFile[i];
string[] lineArray = line.Split(' ');
mainArray[i] = lineArray;
}
//Once you have everything loaded into your arrays, apply your workflow logic.
Hope this helps!

The way I would go about this task is to write a set of unit tests based on your requirements, then make them pass one at a time (having one test per requirement).
As jaywayco suggested, I would read the file into an array of lines, then implement each of your rules as a line transformation method which can be tested in isolation. I would probably separate out the method which can select which transformation(s) to apply. Then loop over the lines and apply the transformations.