I'm new to C# and I have a problem. I would like to have the content of a file written to a RichTextBox, but the StreamReader.ReadLine method reads only the first line.
How can I solve this?
Probably the easiest way to do this would be to use the System.IO.File class's ReadAllText method:
myRichTextBox.Text = File.ReadAllText(filePath);
This class has a bunch of static methods that wrap the StreamReader class for you that make reading and writing to files quite easy.
There are several ways to read a file. If you want to it with a StreamReader and want to read the whole file, this could be a solution:
using System;
using System.IO;
class Test
{
public static void Main()
{
try
{
// Create an instance of StreamReader to read from a file.
// The using statement also closes the StreamReader.
using (StreamReader sr = new StreamReader("TestFile.txt"))
{
string line;
// Read and display lines from the file until the end of
// the file is reached.
while ((line = sr.ReadLine()) != null)
{
Console.WriteLine(line);
}
}
}
catch (Exception e)
{
// Let the user know what went wrong.
Console.WriteLine("The file could not be read:");
Console.WriteLine(e.Message);
}
}
}
You could edit the part were the output of the console happens. Here it would be possible to concatenate the string for your RichTextbox with
text += Environment.NewLine + line;
Related
I'm using the two functions to read and write huge files (write to multiple files). I want to keep the file operation in the functions because the lines may be read/write from other sources.
Update:
C# doesn't really have coroutine. Is it a good use case for Reactive extensions?
foreach (var line in ReadFrom("filename"))
{
try
{
.... // Some actions based on the line
var l = .....
WriteTo("generatedFile1", l);
}
catch (Exception e)
{
var l = ..... // get some data from line, e and other objects etc.
WriteTo("generatedFile2", l);
}
}
The following function open the file once until all the lines are read and then close and release the resource.
private static IEnumerable<string> ReadFrom(string file)
{
string line;
using (var reader = File.OpenText(file))
{
while ((line = reader.ReadLine()) != null)
yield return line;
}
}
However, the following function, which write the lines instead of read lines, open and close the file for each line it writes. Is it possible to implement it in a way so it only open the file once and continue to write to the file until EOF is sent?
private static void WriteTo(string file, string line)
{
if (!File.Exists(file)) // Remove and recreate the file if existing
using (var tw = File.CreateText(file))
{
tw.WriteLine(line);
}
else
using (var tw = new StreamWriter(file, true))
{
tw.WriteLine(line);
}
}
Just use File.WriteAllLines. It will write all of the lines in a sequence to a file, and it won't open/close the file for each line.
You can remove the entire second method, and replace the call with var writer = new StreamWriter(file, true), as that constructor creates the file if it does not exist.
You can then use writer.WriteLine() until you're done writing, and Dispose() it afterwards.
The code running on wince 5.0 / .net framework compact 2.0
Always get a exception says:
the process cannot access the file because it is being used by another process.
Really confused as i already encolse the stream in the using statement,so the filestream should be closed automaticly once leave the using block .
//read text
using (StreamReader sr = File.OpenText(fname))
{
string line;
while ((line = sr.ReadLine()) != null)
{
// append into stringbuilder
sb.Append(line);
sb.Append("\n");
}
}
//write text, below code raise the exception.
//if i comment it and re-run the code,exception disappear
using (StreamWriter sw = File.CreateText(fname))
{
sw.Write(sb.ToString());
}
addition:i just want to update the file, read and write. any better way?
sorry guys, the issue is in my code and i confused you here as i dont share that code.
actually because i wrote this in the very beginning of the program
// f is the fileinfo which point to fname as well
string text = f.OpenText().ReadToEnd();
this created a streamreader, not being assigned to any varible, but it's in the heap.so i ignored.
thanks people helpping here. BTW changed code to this then issue gone
using (StreamReader sr = f.OpenText())
{
string text = sr.ReadToEnd();
}
I tested this code on my computer. There is no problem.
Better way. For read and write full file, you can use File.ReadAllText(fname) and File.WriteAllText(fname). And instead of using \n use Environment.NewLine
I'm trying to get my program to read code from a .txt and then read it back to me, but for some reason, it crashes the program when I compile. Could someone let me know what I'm doing wrong? Thanks! :)
using System;
using System.IO;
public class Hello1
{
public static void Main()
{
string winDir=System.Environment.GetEnvironmentVariable("windir");
StreamReader reader=new StreamReader(winDir + "\\Name.txt");
try {
do {
Console.WriteLine(reader.ReadLine());
}
while(reader.Peek() != -1);
}
catch
{
Console.WriteLine("File is empty");
}
finally
{
reader.Close();
}
Console.ReadLine();
}
}
I don't like your solution for two simple reasons:
1)I don't like gotta Cath 'em all(try catch). For avoing check if the file exist using System.IO.File.Exist("YourPath")
2)Using this code you haven't dispose the streamreader. For avoing this is better use the using constructor like this: using(StreamReader sr=new StreamReader(path)){ //Your code}
Usage example:
string path="filePath";
if (System.IO.File.Exists(path))
using (System.IO.StreamReader sr = new System.IO.StreamReader(path))
{
while (sr.Peek() > -1)
Console.WriteLine(sr.ReadLine());
}
else
Console.WriteLine("The file not exist!");
If your file is located in the same folder as the .exe, all you need to do is StreamReader reader = new StreamReader("File.txt");
Otherwise, where File.txt is, put the full path to the file. Personally, I think it's easier if they are in the same location.
From there, it's as simple as Console.WriteLine(reader.ReadLine());
If you want to read all lines and display all at once, you could do a for loop:
for (int i = 0; i < lineAmount; i++)
{
Console.WriteLine(reader.ReadLine());
}
Use the code below if you want the result as a string instead of an array.
File.ReadAllText(Path.Combine(winDir, "Name.txt"));
Why not use System.IO.File.ReadAllLines(winDir + "\Name.txt")
If all you're trying to do is display this as output in the console, you could do that pretty compactly:
private static string winDir = Environment.GetEnvironmentVariable("windir");
static void Main(string[] args)
{
Console.Write(File.ReadAllText(Path.Combine(winDir, "Name.txt")));
Console.Read();
}
using(var fs = new FileStream(winDir + "\\Name.txt", FileMode.Open, FileAccess.Read))
{
using(var reader = new StreamReader(fs))
{
// your code
}
}
The .NET framework has a variety of ways to read a text file. Each have pros and cons... lets go through two.
The first, is one that many of the other answers are recommending:
String allTxt = File.ReadAllText(Path.Combine(winDir, "Name.txt"));
This will read the entire file into a single String. It will be quick and painless. It comes with a risk though... If the file is large enough, you may run out of memory. Even if you can store the entire thing into memory, it may be large enough that you will have paging, and will make your software run quite slowly. The next option addresses this.
The second solution allows you to work with one line at a time and not load the entire file into memory:
foreach(String line in File.ReadLines(Path.Combine(winDir, "Name.txt")))
// Do Work with the single line.
Console.WriteLine(line);
This solution may take a little longer for files because it's going to do work MORE OFTEN with the contents of the file... however, it will prevent awkward memory errors.
I tend to go with the second solution, but only because I'm paranoid about loading huge Strings into memory.
Lets say i have a text file with following content:
Hello!
How are you?
I want to call the file via a simple application that produces an output file with the following contents:
buildLetter.Append("Hello!").AppendLine();
buildLetter.Append("How are you?").AppendLine();
As you see, every line should be put between " ".
Any help will be appreciated.
void ConvertFile(string inPath, string outPath)
{
using (var reader = new StreamReader(inPath))
using (var writer = new StreamWriter (outPath))
{
string line = reader.ReadLine();
while (line != null)
{
writer.WriteLine("buildLetter.Append(\"{0}\").AppendLine();",line.Trim());
line = reader.ReadLine ();
}
}
}
You should add some I/O exception handling on your own.
If you want to append "" to each line you could try combining the ReadAllLines and WriteAllLines methods:
File.WriteAllLines(
"output.txt",
File
.ReadAllLines("input.txt")
.Select(line => string.Format("\"{0}\"", line))
.ToArray()
);
Notice that this loads the whole file contents into memory so it wouldn't work well with very large files. In this case stream readers and writers are more adapted.
Use the StreamReader class from System.IO
Refer this link for sample code
All you probably need to do is change the line
Console.WriteLine(sr.ReadLine());
to
Console.WriteLine(""""" + sr.ReadLine() + """""); // handwritten code - not tested :-)
For a small text files this works for me.
private void EditFile(string path, string oldText, string newText)
{
string content = File.ReadAllText(path);
content = contenido.Replace(oldText, newText);
File.WriteAllText(path, content);
}
I have a text file that contains about 100000 articles.
The structure of file is:
.Document ID 42944-YEAR:5
.Date 03\08\11
.Cat political
Article Content 1
.Document ID 42945-YEAR:5
.Date 03\08\11
.Cat political
Article Content 2
I want to open this file in c# for processing it line by line.
I tried this code:
String[] FileLines = File.ReadAllText(
TB_SourceFile.Text).Split(Environment.NewLine.ToCharArray());
But it says:
Exception of type
'System.OutOfMemoryException' was
thrown.
The question is How can I open this file and read it line by line.
File Size: 564 MB (591,886,626 bytes)
File Encoding: UTF-8
File contains Unicode characters.
You can open the file and read it as a stream rather than loading everything into memory all at once.
From MSDN:
using System;
using System.IO;
class Test
{
public static void Main()
{
try
{
// Create an instance of StreamReader to read from a file.
// The using statement also closes the StreamReader.
using (StreamReader sr = new StreamReader("TestFile.txt"))
{
String line;
// Read and display lines from the file until the end of
// the file is reached.
while ((line = sr.ReadLine()) != null)
{
Console.WriteLine(line);
}
}
}
catch (Exception e)
{
// Let the user know what went wrong.
Console.WriteLine("The file could not be read:");
Console.WriteLine(e.Message);
}
}
}
Your file is too large to be read into memory in one go, as File.ReadAllText is trying to do. You should instead read the file line by line.
Adapted from MSDN:
string line;
// Read the file and display it line by line.
using (StreamReader file = new StreamReader(#"c:\yourfile.txt"))
{
while ((line = file.ReadLine()) != null)
{
Console.WriteLine(line);
// do your processing on each line here
}
}
In this way, no more than a single line of the file is in memory at any one time.
If you are using .NET Framework 4, there is a new static method on System.IO.File called ReadLines that returns an IEnumerable of string. I believe it was added to the framework for this exact scenario; however, I have yet to use it myself.
MSDN Documentation - File.ReadLines Method (String)
Related Stack Overflow Question - Bug in the File.ReadLines(..) method of the .net framework 4.0
Something like this:
using (var fileStream = File.OpenText(#"path to file"))
{
do
{
var fileLine = fileStream.ReadLine();
// process fileLine here
} while (!fileStream.EndOfStream);
}