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Read a text file until a line contains some string file, then again keep reading next lines until another string is encountered

I have to read a text file and if line contains ".engineering $name" then look for line which contains ".default" and do some operation with this line. I need to keep reading lines until I find ".default" in a set of lines. (This set is like, until I hit next ".engineering"). Loop continue like this again for next ".engineering $name"
Note:
".engineering" keyword is fixed string, $name reading dynamically,
".default" is fixed string,
I am able to do the first part that is reading line which contains ".engineering $name"
I am unable to get logic for next part, finding ".default" until it hits next ".engineering"
Looking for logic or code for this logic in C#. Thank you
Code:
using (var stream = new FileStream(path, FileMode.Open, FileAccess.Read))
using (var reader = new StreamReader(stream))
{
while (!reader.EndOfStream)
{
string[] def_arr = null;
var line1 = reader.ReadLine();
if (line1.Contains(".engineering " + name + " ") && !reader.EndOfStream)
{
var nextLine = reader.ReadLine(); // nextLine contains ".default"
def_arr = nextLine.Split(' ');
def_val = def_arr[1].Replace("\"", "");
port_DefaultValues.Add(name + ", " + def_val);
}
}
}
var nextLine is the line containing ".default". I have coded like immidiate next line of finding ".engineering" is having ".default".But it is not always the case. ".default" can be in any line before it hits next ."engineering".
I hope the problem statement is clear.

Try this code -
using (var stream = new FileStream(path, FileMode.Open, FileAccess.Read))
using (var reader = new StreamReader(stream))
{
while (!reader.EndOfStream)
{
string[] def_arr = null;
var line1 = reader.ReadLine();
if (line1.Contains(".engineering " + name + " ") && !reader.EndOfStream)
{
var nextLine = reader.ReadLine(); // nextLine contains ".default"
while (!nextLine.Contains(".default") && !reader.EndOfStream)
{
nextLine = reader.ReadLine();
}
def_arr = nextLine.Split(' ');
def_val = def_arr[1].Replace("\"", "");
port_DefaultValues.Add(name + ", " + def_val);
}
}
}
I have just added a loop that will keep reading the next line until it encounters .default. Keep in mind it will throw exception if that is not found in rest of the file.

Replacing a certain word in a text file

I know this has been asked a few times, but I have seen a lot of regex etc., and I'm sure there is another way to do this with just a stream reader/writer. Below is my code. I'm trying to replace "tea" with the word "cabbage". Can somebody help? I believe I have the wrong syntax.
namespace Week_9_Exer_4
{
class TextImportEdit
{
public void EditorialControl()
{
string fileName;
string lineReadFromFile;
Console.WriteLine("");
// Ask for the name of the file to be read
Console.Write("Which file do you wish to read? ");
fileName = Console.ReadLine();
Console.WriteLine("");
// Open the file for reading
StreamReader fileReader = new StreamReader("C:\\Users\\Greg\\Desktop\\Programming Files\\story.txt");
// Read the lines from the file and display them
// until a null is returned (indicating end of file)
lineReadFromFile = fileReader.ReadLine();
Console.WriteLine("Please enter the word you wish to edit out: ");
string editWord = Console.ReadLine();
while (lineReadFromFile != null)
{
Console.WriteLine(lineReadFromFile);
lineReadFromFile = fileReader.ReadLine();
}
String text = File.ReadAllText("C:\\Users\\Greg\\Desktop\\Programming Files\\story.txt");
fileReader.Close();
StreamWriter fileWriter = new StreamWriter("C:\\Users\\Greg\\Desktop\\Programming Files\\story.txt", false);
string newText = text.Replace("tea", "cabbage");
fileWriter.WriteLine(newText);
fileWriter.Close();
}
}
}

If you don't care about memory usage:
string fileName = #"C:\Users\Greg\Desktop\Programming Files\story.txt";
File.WriteAllText(fileName, File.ReadAllText(fileName).Replace("tea", "cabbage"));
If you have a multi-line file that doesn't randomly split words at the end of the line, you could modify one line at a time in a more memory-friendly way:
// Open a stream for the source file
using (var sourceFile = File.OpenText(fileName))
{
// Create a temporary file path where we can write modify lines
string tempFile = Path.Combine(Path.GetDirectoryName(fileName), "story-temp.txt");
// Open a stream for the temporary file
using (var tempFileStream = new StreamWriter(tempFile))
{
string line;
// read lines while the file has them
while ((line = sourceFile.ReadLine()) != null)
{
// Do the word replacement
line = line.Replace("tea", "cabbage");
// Write the modified line to the new file
tempFileStream.WriteLine(line);
}
}
}
// Replace the original file with the temporary one
File.Replace("story-temp.txt", "story.txt", null);

In the end i used this : Hope it can help out others
public List<string> EditorialResponse(string fileName, string searchString, string replacementString)
{
List<string> list = new List<string>();
using (StreamReader reader = new StreamReader(fileName))
{
string line;
while ((line = reader.ReadLine()) != null)
{
line = line.Replace(searchString, replacementString);
list.Add(line);
Console.WriteLine(line);
}
reader.Close();
}
return list;
}
}
class Program
{
static void Main(string[] args)
{
TextImportEdit tie = new TextImportEdit();
List<string> ls = tie.EditorialResponse(#"C:\Users\Tom\Documents\Visual Studio 2013\story.txt", "tea", "cockrel");
StreamWriter writer = new StreamWriter(#"C:\Users\Tom\Documents\Visual Studio 2013\story12.txt");
foreach (string line in ls)
{
writer.WriteLine(line);
}
writer.Close();
}
}
}

Read last empty line of a text file

I have funny problem - I tried several scripts that will read text files, and that's ok.
Problem occur when text file have empty line at the end - that line is "ignored".
Code I use is "usual" code for file read, like next one:
string fullFileName;
fullFileName = "myFile.txt";
var lines = File.ReadAllLines(fullFileName);
string fileContent = null;
bool firstLine = true;
foreach (var line in lines) {
if (firstLine != true)
{
//textBox1.Text += System.Environment.NewLine;
fileContent += System.Environment.NewLine;
}
else
{
firstLine = false;
}
//textBox1.Text += line;
fileContent += line;
}
textBox1.Text = fileContent;
So, if last line of file myFile.txt is empty, it is not showed in a TextBox.
Can you help me where is a problem?

I think you could avoid the loop altogether and just do:
textBox1.Text = File.ReadAllText(fullFileName);
This will preserve all the newlines.

It is a problem with the file representation, not with ReadAllLines.
See this thread: http://www.pcreview.co.uk/forums/file-readalllines-doesnt-read-last-blank-line-weird-t3765200.html

Other solution:
using (FileStream fileStream = File.OpenRead("C:\myFile.txt"))
using (StreamReader streamReader = new StreamReader(fileStream))
{
string fileContent = streamReader.ReadToEnd();
textBox1.Text = fileContent;
}

File.ReadAllLines(fullFileName);
does not reads carriage return ('\r'). i think your last line contains only carriage return thats why its not being read. put space in last line to check.
http://msdn.microsoft.com/en-us/library/s2tte0y1.aspx

C# read line from file with StreamReader with DownloadFileAsync

I am having a problem reading file with StreamReader and while line != null add to textBox1
Code:
using(StreamReader reader = new StreamReader("lastupdate.txt"))
{
string line;
while((line = reader.ReadLine()) != null)
{
textBox1.Text = line;
}
reader.Close();
}
It's not working and I don't know why. I tried to use using StreamReader, I download the file from the URL and I can see in the folder that the file is downloaded. The lastupdate.txt is 1KB in size.
This is my current working code with MessageBox. If I remove the MessageBox, the code doesn't work. It needs some kind of wait or I don't know:
WebClient client = new WebClient();
client.DownloadFileAsync(new Uri(Settings.Default.patchCheck), "lastupdate.txt"); // ok
if(File.Exists("lastupdate.txt"))
{
MessageBox.Show("Lastupdate.txt exist");
using(StreamReader reader = new StreamReader("lastupdate.txt"))
{
string line;
while((line = reader.ReadLine()) != null)
{
textBox1.Text = line;
MessageBox.Show(line.ToString());
}
reader.Close();
}
File.Delete("lastupdate.txt");
}

Try :
StringBuilder sb = new StringBuilder();
using (StreamReader sr = new StreamReader("lastupdate.txt"))
{
while (sr.Peek() >= 0)
{
sb.Append(sr.ReadLine());
}
}
textbox.Text = sb.Tostring();

If you want the text in the text box it would be much more effective to read all of it and then put it into the text box:
var lines = File.ReadAllLines("lastupdate.txt");
textBox1.Lines = lines; //assuming multi-line text box
or:
textBox1.Text = File.ReadAllText("lastupdate.txt");
Edit:
After latest update - you are downloading the file asynchronously - it might not even be there, only partially there or in a state in-between when your code executes.
If you just want the text string in the file don't download it, use DownloadString instead:
string text = "";
using (WebClient wc = new WebClient())
{
text = wc.DownloadString(new Uri(Settings.Default.patchCheck));
}
textBox1.Text = text;

Try this :
using(StreamReader reader = new StreamReader(Path))
{
string line = reader.ReadLine();
while(line != null)
{
textBox1.Text += line;
line = reader.ReadLine()
}
reader.Close();
}

Web Client has a rather bizarre DownloadFileAsync method. The return type is void, so it is not awaitable. Also, that means we do not even get a Task, so ContinueWith is not possible. That leaves us with using the DownloadFileCompleted event.
const string FileName = "lastupdate.txt";
private void DownloadLastUpdate() {
var client = new WebClient();
client.DownloadFileCompleted += ( s, e ) => {
this.UpdateTextBox( e.Error );
client.Dispose();
};
client.DownloadFileAsync( new Uri( Settings.Default.patchCheck ), FileName );
}
I went with an optional exception parameter to relay any exception messages. Feel free to refactor as desired. File.ReadLines yields text line by line, so large files should not use very much memory.
private void UpdateTextBox( Exception exception = null ) {
textBox1.Text = string.Empty;
if ( exception != null ) {
textBox1.Text = exception.Message;
return;
}
if ( !File.Exists( FileName ) ) {
textBox1.Text = string.Format( "File '{0}' does not exist.", FileName );
return;
}
var lines = File.ReadLines( FileName );
textBox1.Text = string.Join( Environment.NewLine, lines );
}

the answer given above is correct, but in your piece of code, just change 1 line:
textBox1.Text += line;

Delete specific line from a text file?

I need to delete an exact line from a text file but I cannot for the life of me workout how to go about doing this.
Any suggestions or examples would be greatly appreciated?
Related Questions
Efficient way to delete a line from a text file (C#)

If the line you want to delete is based on the content of the line:
string line = null;
string line_to_delete = "the line i want to delete";
using (StreamReader reader = new StreamReader("C:\\input")) {
using (StreamWriter writer = new StreamWriter("C:\\output")) {
while ((line = reader.ReadLine()) != null) {
if (String.Compare(line, line_to_delete) == 0)
continue;
writer.WriteLine(line);
}
}
}
Or if it is based on line number:
string line = null;
int line_number = 0;
int line_to_delete = 12;
using (StreamReader reader = new StreamReader("C:\\input")) {
using (StreamWriter writer = new StreamWriter("C:\\output")) {
while ((line = reader.ReadLine()) != null) {
line_number++;
if (line_number == line_to_delete)
continue;
writer.WriteLine(line);
}
}
}

The best way to do this is to open the file in text mode, read each line with ReadLine(), and then write it to a new file with WriteLine(), skipping the one line you want to delete.
There is no generic delete-a-line-from-file function, as far as I know.

One way to do it if the file is not very big is to load all the lines into an array:
string[] lines = File.ReadAllLines("filename.txt");
string[] newLines = RemoveUnnecessaryLine(lines);
File.WriteAllLines("filename.txt", newLines);

Hope this simple and short code will help.
List linesList = File.ReadAllLines("myFile.txt").ToList();
linesList.RemoveAt(0);
File.WriteAllLines("myFile.txt"), linesList.ToArray());
OR use this
public void DeleteLinesFromFile(string strLineToDelete)
{
string strFilePath = "Provide the path of the text file";
string strSearchText = strLineToDelete;
string strOldText;
string n = "";
StreamReader sr = File.OpenText(strFilePath);
while ((strOldText = sr.ReadLine()) != null)
{
if (!strOldText.Contains(strSearchText))
{
n += strOldText + Environment.NewLine;
}
}
sr.Close();
File.WriteAllText(strFilePath, n);
}

You can actually use C# generics for this to make it real easy:
var file = new List<string>(System.IO.File.ReadAllLines("C:\\path"));
file.RemoveAt(12);
File.WriteAllLines("C:\\path", file.ToArray());

This can be done in three steps:
// 1. Read the content of the file
string[] readText = File.ReadAllLines(path);
// 2. Empty the file
File.WriteAllText(path, String.Empty);
// 3. Fill up again, but without the deleted line
using (StreamWriter writer = new StreamWriter(path))
{
foreach (string s in readText)
{
if (!s.Equals(lineToBeRemoved))
{
writer.WriteLine(s);
}
}
}

Read and remember each line
Identify the one you want to get rid
of
Forget that one
Write the rest back over the top of
the file

I cared about the file's original end line characters ("\n" or "\r\n") and wanted to maintain them in the output file (not overwrite them with what ever the current environment's char(s) are like the other answers appear to do). So I wrote my own method to read a line without removing the end line chars then used it in my DeleteLines method (I wanted the option to delete multiple lines, hence the use of a collection of line numbers to delete).
DeleteLines was implemented as a FileInfo extension and ReadLineKeepNewLineChars a StreamReader extension (but obviously you don't have to keep it that way).
public static class FileInfoExtensions
{
public static FileInfo DeleteLines(this FileInfo source, ICollection<int> lineNumbers, string targetFilePath)
{
var lineCount = 1;
using (var streamReader = new StreamReader(source.FullName))
{
using (var streamWriter = new StreamWriter(targetFilePath))
{
string line;
while ((line = streamReader.ReadLineKeepNewLineChars()) != null)
{
if (!lineNumbers.Contains(lineCount))
{
streamWriter.Write(line);
}
lineCount++;
}
}
}
return new FileInfo(targetFilePath);
}
}
public static class StreamReaderExtensions
{
private const char EndOfFile = '\uffff';
/// <summary>
/// Reads a line, similar to ReadLine method, but keeps any
/// new line characters (e.g. "\r\n" or "\n").
/// </summary>
public static string ReadLineKeepNewLineChars(this StreamReader source)
{
if (source == null)
throw new ArgumentNullException(nameof(source));
char ch = (char)source.Read();
if (ch == EndOfFile)
return null;
var sb = new StringBuilder();
while (ch != EndOfFile)
{
sb.Append(ch);
if (ch == '\n')
break;
ch = (char)source.Read();
}
return sb.ToString();
}
}

Are you on a Unix operating system?
You can do this with the "sed" stream editor. Read the man page for "sed"

What?
Use file open, seek position then stream erase line using null.
Gotch it? Simple,stream,no array that eat memory,fast.
This work on vb.. Example search line culture=id where culture are namevalue and id are value and we want to change it to culture=en
Fileopen(1, "text.ini")
dim line as string
dim currentpos as long
while true
line = lineinput(1)
dim namevalue() as string = split(line, "=")
if namevalue(0) = "line name value that i want to edit" then
currentpos = seek(1)
fileclose()
dim fs as filestream("test.ini", filemode.open)
dim sw as streamwriter(fs)
fs.seek(currentpos, seekorigin.begin)
sw.write(null)
sw.write(namevalue + "=" + newvalue)
sw.close()
fs.close()
exit while
end if
msgbox("org ternate jua bisa, no line found")
end while
that's all..use #d