This question seems to have been asked a million times around the web, but I cannot find an answer which will work for me.
Basically, I have a CSV file which has a number of columns (say two). The program goes through each row in the CSV file, taking the first column value, then asks the user for the value to be placed in the second column. This is done on a handheld running Windows 6. I am developing using C#.
It seems a simple thing to do. But I cant seem to add text to a line.
I cant use OleDb, as System.Data.Oledb isnt in the .Net version I am using. I could use another CSV file, and when they complete each line, it writes it to another CSV file. But the problems with that are - The file thats produced at the end needs to contain EVERY line (so what if they pull the batterys out half way). And what if they go back, to continue doing this another time, how will the program know where to start back from.
For every row, open the output file, append the new row to it, and then close the output file. To restart, count the number of rows in the existing output file from the previous run, which will give you your starting in the input file (i.e., skip that number of rows in the input file).
Edit: right at the start, use System.IO.File.Copy to copy the input file to the output file, so you have all the file in case of failure. Now open the input file, read a line, convert it, use File.ReadAllLines to read ALL of the output file into an array, replace the line you have changed at the right index in the array, then use File.WriteAllLines to write out the new output file.
Something like this:
string inputFileName = ""; // Use a sensible file name.
string outputFileName = ""; // Use a sensible file name.
File.Copy(inputFileName, outputFileName, true);
using (StreamReader reader = new StreamReader(inputFileName))
{
string line = null;
int inputLinesIndex = 0;
while ((line = reader.ReadLine()) != null)
{
string convertedLine = ConvertLine(line);
string[] outputFileLines = File.ReadAllLines(outputFileName);
if (inputLinesIndex < outputFileLines.Length)
{
outputFileLines[inputLinesIndex] = convertedLine;
File.WriteAllLines(outputFileName, outputFileLines);
}
inputLinesIndex++;
}
}
Related
I want to edit some text files automatically, but I don't know what to used to do it.
I want to open a file, check all lines, if one line begins with a 'C', I remove first 39-characters, etc .. then save all the file with an other name.
I already have a portion of code :
var car = ligne[0];
if(car != 'C') { continue; }
ligne.Remove(0, 39);
I use StreamReader to read, but what is the simple way to read and save in another file ?
Try File.ReadAllLines, which opens a file, reads everything, closes the file and returns an array containing all lines.
Do your processing....
Then File.WriteAllLines to open a file, write data, and close the file.
When modifying a file, is it always necessary to rewrite the entire file or is it possible to find and change some small part of a file without having to rewrite the whole thing?
If you're not inserting or deleting data, then you don't need to rewrite the file. You will be replacing existing bytes with new values, or appending to the file.
If you need to insert or delete, you only need to rewrite the file from that point onwards. The only time you would need to rewrite the entire file is if you are inserting bytes at the beginning.
It's okay to open a file with both read and write permissions. That way you can search the file for whatever you're looking for, and once you have the position you can seek to it (from memory, the write pointer is separate from the read pointer) and overwrite data to your heart's content =)
If you're not changing the length of the data, you can always just seek to the appropriate position in the file, and write a new set of bytes. This replaces whatever bytes where originally there.
There are two possible ways:
when you use StreamWriter sw = new StreamWriter it will delete the data from file.
To change only, you can store the file data in a List<string>. This works nice for me:
List<string> lines_list = new List<string>();
int file_l = 0
StreamReader sr_temp = new StreamReader(_path);
string line;
while ((line = sr_temp.ReadLine()) != null)
{
lines_list.Add(line);
file_l++;
}
sr_temp.Close();
StreamWriter sw = new StreamWriter(_path);
for (int i = 0; i < file_l; i++)
{
sw.WriteLine(lines_list[i]);
}
//here you add some data
sw.Close();
I have a program that reads text files filled with code designed to be executed line by line by the program, like a batch file. The problem is that I don't no how to do the line executing part. Here is my code, I thought using the \r would fool the console. But it just shows me a list of lines in the file.
if (tok[0] == "read" && length == 2)
{
try
{
StreamReader tr = new StreamReader(#"C:\Users\Public\"+tok[1]+".txt");
while (!tr.EndOfStream)
{
Console.WriteLine(tr.ReadLine());
}
}
catch
{
Console.WriteLine("No such text file.\n");
}
Prompt();
}
If I knew what to search for to fix my problem in Google, I would have. But I've got no idea.
Thanks
EDIT - My program is a crude synthesizer. It takes inputs in the form of 440 5, or 415 2. The first number is frequency, the second duration. What I'm wanting to do is read text files, which my code does, and execute the sound info line by line, which it doesn't, hence my question. It works perfectly fine from standard input.
Audio synthesis is not straightforward, there used to be
Console.Beep(frequency,duration);
but that's using the PC speaker most systems don't have anymore - here's an example though using DirectSound to achieve something close to what you want.
To read the frequency and duration from your text file you can use something like this (splitting on space):
StreamReader tr = new StreamReader(#"test.txt");
while(!tr.EndOfStream)
{
string[] parts = tr.ReadLine().Split(new[]{' '});
int frequency = Convert.ToInt32(parts[0]);
int duration = Convert.ToInt32(parts[1]);
}
You should load your code and compile it in the runtime.
Check out following examples:
http://www.csharpfriends.com/articles/getarticle.aspx?articleid=118
http://www.codeproject.com/KB/dotnet/evaluator.aspx
EDIT:
You should use Process.Start(cmd); to execute commands in the shell. Here I've found few nice examples: http://dotnetperls.com/process-start
If your program works fine using Standard Input just pass the text file to it like this:
yourprogram.exe < textFile.txt
Then the contents of the text file will be passed to your program on Standard Input.
I want to insert the data at some positions in the text file without actually overwriting on the existing data. I have two text file. "one.txt" file have 1000 lines, "two.txt" file have 10000 lines. I want to read "one.txt" file content and insert into first 1000 lines of "two.txt" file content(Append the content of "one.txt" to the beginning of "two.txt").
Criteria:
Minimum code .
Less Memory consumption(irrespective of programming language )
Performance (will be considered based on size of the file).
just open up a streamreader for the first file, and a stream writer (in append mode) for the second file. As your reading the first 1000 lines from the first file, insert them into the second.
Something like this:
StreamReader sr = new StreamReader("one.txt");
StreamWriter sw = new StreamWriter("two.txt", true); //true for append
index i = 0;
while (i < 1000) {
sw.WriteLine(sr.ReadLine());
i++;
}
You may want to check for end of file on the StreamReader, but this will give you the general idea....
Based on the new information in OP:
You can use this same type of method, but just create a brand new file, reading the data from the first file, followed by the data from the second file. Once it's inside the new file, replace the original "two.txt".
If you're not limited to c# you can just do the following from a windows command line:
copy one.txt + two.txt three.txt
This would create the file you want, but it would be called three.txt. If you must have it in two.txt, you could simply rename two.txt to something else first and then do the copy append with two.txt as the third parm.
If you only have to do this once, here is some code that will do what you want. I did not compile this, but I believe there are no issues.
string[] linesOne = File.ReadAllLines(pathToFile1);
string[] linesTwo = File.ReadAllLines(pathToFile2);
List<string> result = new List<string>();
for(int i=0;i<1000;i++)
{
result.Add(linesOne[i]);
}
result.AddRange(linesTwo);
File.WriteAllLines(pathToFile2, result);
Hope this gets you started.
Bob
//Introduction
Hey, Welcome.....
This is the tutorial
//EndIntro
//Help1
Select a Stock
To use this software you first need to select the stock. To do that, simply enter the stock symbol in the stock text-box (such as "MSFT").
To continue enter "MSFT" in the stock symbol box.
//EndHelp1
//Help2
Download Stock Data
Next step is to to download the stock data from the online servers. To start the process simply press the "Update" button or hit the <ENTER> key.
After stock data is downloaded the "Refresh" button will appear instead. Press it when you want to refresh the data with the latest quote.
To continue make sure you are online and press the "Update" button
//EndHelp2
First time I want to display the content between //Introduction and //EndIntro then second time the content between //Help1 and //EndHelp1 and so on.
That's a very open-ended question - what sort of file? To read binary data from it you'd usually use:
using (Stream stream = File.OpenRead(filename))
{
// Read from the stream here
}
or
byte[] data = File.ReadAllBytes(filename);
To read text you could use any of:
using (TextReader reader = File.OpenText(filename))
{
// Read from the reader
}
or
string text = File.ReadAllText(filename);
or
string[] lines = File.ReadAllLines(filename);
If you could give more details about the kind of file you want to read, we could help you with more specific advice.
EDIT: To display content from an RTF file, I suggest you load it as text (but be careful of the encoding - I don't know what encoding RTF files use) and then display it in a RichTextBox control by setting the Rtf property. Make the control read-only to avoid the user editing the control (although if the user does edit the control, that wouldn't alter the file anyway).
If you only want to display part of the file, I suggest you load the file, find the relevant bit of text, and use it appropriately with the Rtf property. If you load the whole file as a single string you can use IndexOf and Substring to find the relevant start/end markers and take the substring between them; if you read the file as multiple lines you can look for the individual lines as start/end markers and then concatenate the content between them.
(I also suggest that next time you ask a question, you include this sort of detail to start with rather than us having to tease it out of you.)
EDIT: As Mark pointed out in a comment, RTF files should have a header section. What you've shown isn't really an RTF file in the first place - it's just plain text. If you really want RTF, you could have a header section and then the individual sections. A better alternative would probably be to have separate files for each section - it would be cleaner that way.
Not sure I understand your question correctly. But you can read and write content using System.IO.StreamReader and StreamWriter classes
string content = string.Empty;
using (StreamReader sr = new StreamReader("C:\\sample.txt"))
{
content = sr.ReadToEnd();
}
using (StreamWriter sw = new StreamWriter("C:\\Sample1.txt"))
{
sw.Write(content);
}
Your question needs more clarification. Look at System.IO.File for many ways to read data.
The easiest way of reading a text file is probably this:
string[] lines = File.ReadAllLines("filename.txt");
Note that this automatically handles closing the file so no using statement is need.
If the file is large or you don't need all lines you might prefer to reading the text file in a streaming manner:
using (StreamReader streamReader = File.OpenText(path))
{
while (true)
{
string line = streamReader.ReadLine();
if (line == null)
{
break;
}
// Do something with line...
}
}
If the file contains XML data you might want to open it using an XML parser:
XDocument doc = XDocument.Load("input.xml");
var nodes = doc.Descendants();
There are many, many other ways to read data from a file. Could you be more specific about what the file contains and what information you need to read?
Update: To read an RTF file and display it:
richTextBox.Rtf = File.ReadAllText("input.rtf");