There are a lot of different ways to read and write files (text files, not binary) in C#.
I just need something that is easy and uses the least amount of code, because I am going to be working with files a lot in my project. I only need something for string since all I need is to read and write strings.
Use File.ReadAllText and File.WriteAllText.
MSDN example excerpt:
// Create a file to write to.
string createText = "Hello and Welcome" + Environment.NewLine;
File.WriteAllText(path, createText);
...
// Open the file to read from.
string readText = File.ReadAllText(path);
In addition to File.ReadAllText, File.ReadAllLines, and File.WriteAllText (and similar helpers from File class) shown in another answer you can use StreamWriter/StreamReader classes.
Writing a text file:
using(StreamWriter writetext = new StreamWriter("write.txt"))
{
writetext.WriteLine("writing in text file");
}
Reading a text file:
using(StreamReader readtext = new StreamReader("readme.txt"))
{
string readText = readtext.ReadLine();
}
Notes:
You can use readtext.Dispose() instead of using, but it will not close file/reader/writer in case of exceptions
Be aware that relative path is relative to current working directory. You may want to use/construct absolute path.
Missing using/Close is very common reason of "why data is not written to file".
FileStream fs = new FileStream(txtSourcePath.Text,FileMode.Open, FileAccess.Read);
using(StreamReader sr = new StreamReader(fs))
{
using (StreamWriter sw = new StreamWriter(Destination))
{
sw.Writeline("Your text");
}
}
The easiest way to read from a file and write to a file:
//Read from a file
string something = File.ReadAllText("C:\\Rfile.txt");
//Write to a file
using (StreamWriter writer = new StreamWriter("Wfile.txt"))
{
writer.WriteLine(something);
}
using (var file = File.Create("pricequote.txt"))
{
...........
}
using (var file = File.OpenRead("pricequote.txt"))
{
..........
}
Simple, easy and also disposes/cleans up the object once you are done with it.
#AlexeiLevenkov pointed me at another "easiest way" namely the extension method. It takes just a little coding, then provides the absolute easiest way to read/write, plus it offers the flexibility to create variations according to your personal needs. Here is a complete example:
This defines the extension method on the string type. Note that the only thing that really matters is the function argument with extra keyword this, that makes it refer to the object that the method is attached to. The class name does not matter; the class and method must be declared static.
using System.IO;//File, Directory, Path
namespace Lib
{
/// <summary>
/// Handy string methods
/// </summary>
public static class Strings
{
/// <summary>
/// Extension method to write the string Str to a file
/// </summary>
/// <param name="Str"></param>
/// <param name="Filename"></param>
public static void WriteToFile(this string Str, string Filename)
{
File.WriteAllText(Filename, Str);
return;
}
// of course you could add other useful string methods...
}//end class
}//end ns
This is how to use the string extension method, note that it refers automagically to the class Strings:
using Lib;//(extension) method(s) for string
namespace ConsoleApp_Sandbox
{
class Program
{
static void Main(string[] args)
{
"Hello World!".WriteToFile(#"c:\temp\helloworld.txt");
return;
}
}//end class
}//end ns
I would never have found this myself, but it works great, so I wanted to share this. Have fun!
These are the best and most commonly used methods for writing to and reading from files:
using System.IO;
File.AppendAllText(sFilePathAndName, sTextToWrite);//add text to existing file
File.WriteAllText(sFilePathAndName, sTextToWrite);//will overwrite the text in the existing file. If the file doesn't exist, it will create it.
File.ReadAllText(sFilePathAndName);
The old way, which I was taught in college was to use stream reader/stream writer, but the File I/O methods are less clunky and require fewer lines of code. You can type in "File." in your IDE (make sure you include the System.IO import statement) and see all the methods available. Below are example methods for reading/writing strings to/from text files (.txt.) using a Windows Forms App.
Append text to an existing file:
private void AppendTextToExistingFile_Click(object sender, EventArgs e)
{
string sTextToAppend = txtMainUserInput.Text;
//first, check to make sure that the user entered something in the text box.
if (sTextToAppend == "" || sTextToAppend == null)
{MessageBox.Show("You did not enter any text. Please try again");}
else
{
string sFilePathAndName = getFileNameFromUser();// opens the file dailog; user selects a file (.txt filter) and the method returns a path\filename.txt as string.
if (sFilePathAndName == "" || sFilePathAndName == null)
{
//MessageBox.Show("You cancalled"); //DO NOTHING
}
else
{
sTextToAppend = ("\r\n" + sTextToAppend);//create a new line for the new text
File.AppendAllText(sFilePathAndName, sTextToAppend);
string sFileNameOnly = sFilePathAndName.Substring(sFilePathAndName.LastIndexOf('\\') + 1);
MessageBox.Show("Your new text has been appended to " + sFileNameOnly);
}//end nested if/else
}//end if/else
}//end method AppendTextToExistingFile_Click
Get file name from the user via file explorer/open file dialog (you will need this to select existing files).
private string getFileNameFromUser()//returns file path\name
{
string sFileNameAndPath = "";
OpenFileDialog fd = new OpenFileDialog();
fd.Title = "Select file";
fd.Filter = "TXT files|*.txt";
fd.InitialDirectory = Environment.CurrentDirectory;
if (fd.ShowDialog() == DialogResult.OK)
{
sFileNameAndPath = (fd.FileName.ToString());
}
return sFileNameAndPath;
}//end method getFileNameFromUser
Get text from an existing file:
private void btnGetTextFromExistingFile_Click(object sender, EventArgs e)
{
string sFileNameAndPath = getFileNameFromUser();
txtMainUserInput.Text = File.ReadAllText(sFileNameAndPath); //display the text
}
Or, if you are really about lines:
System.IO.File also contains a static method WriteAllLines, so you could do:
IList<string> myLines = new List<string>()
{
"line1",
"line2",
"line3",
};
File.WriteAllLines("./foo", myLines);
It's good when reading to use the OpenFileDialog control to browse to any file you want to read. Find the code below:
Don't forget to add the following using statement to read files: using System.IO;
private void button1_Click(object sender, EventArgs e)
{
if (openFileDialog1.ShowDialog() == DialogResult.OK)
{
textBox1.Text = File.ReadAllText(openFileDialog1.FileName);
}
}
To write files you can use the method File.WriteAllText.
class Program
{
public static void Main()
{
//To write in a txt file
File.WriteAllText("C:\\Users\\HP\\Desktop\\c#file.txt", "Hello and Welcome");
//To Read from a txt file & print on console
string copyTxt = File.ReadAllText("C:\\Users\\HP\\Desktop\\c#file.txt");
Console.Out.WriteLine("{0}",copyTxt);
}
}
private void Form1_Load(object sender, EventArgs e)
{
//Write a file
string text = "The text inside the file.";
System.IO.File.WriteAllText("file_name.txt", text);
//Read a file
string read = System.IO.File.ReadAllText("file_name.txt");
MessageBox.Show(read); //Display text in the file
}
Reading from file
string filePath = #"YOUR PATH";
List<string> lines = File.ReadAllLines(filePath).ToList();
Writing to file
List<string> lines = new List<string>();
string a = "Something to be written"
lines.Add(a);
File.WriteAllLines(filePath, lines);
Simply:
String inputText = "Hello World!";
File.WriteAllText("yourfile.ext",inputText); //writing
var outputText = File.ReadAllText("yourfile.ext"); //reading
You're looking for the File, StreamWriter, and StreamReader classes.
Related
Been looking through other people's answers and nothing seems to work.
Here is my code:
public void TaskOnClick() //getting multi-values
{
foreach (string inputJson in File.ReadLines("Assets/Text/multi-import.txt"))
{
string temperature = GetTemperatureByRegex(inputJson);
Debug.Log(temperature);
string filename = "Assets/Text/TEMP/multi-export.txt";
{
using (StreamWriter writeFile = new StreamWriter(filename, false))
{
writeFile.AutoFlush = true;
Console.SetOut(writeFile);
writeFile.WriteLineAsync(temperature.ToString());
}
}
}
}
The idea is that my parsing script gets my data and then streamwriter writes the data to a txt file. Problem is that streamwriter keeps appending the txt file instead of overwriting the file.
Whenever I try to use filestream it overwrites the file, yes, but only the first line of the data gets written, no matter what I tried.
My username speaks for itself...
What you do wrong is creating StreamWriter inside a loop. If you provide an overwrite settings it will only write 1 line.
public void TaskOnClick() //getting multi-values
{
string filename = "Assets/Text/TEMP/multi-export.txt";
using (StreamWriter writeFile = new StreamWriter(filename, false))
{
foreach (string inputJson in File.ReadLines("Assets/Text/multi-import.txt"))
{
string temperature = GetTemperatureByRegex(inputJson);
Debug.Log(temperature);
writeFile.AutoFlush = true;
Console.SetOut(writeFile);
writeFile.WriteLine(temperature.ToString());
}
}
}
But there is a shorter way of doing this with the help of LINQ.
public void TaskOnClick() //getting multi-values
{
string filename = "Assets/Text/TEMP/multi-export.txt";
var tempratures = File.ReadAllLines("Assets/Text/multi-import.txt")
.Select(GetTemperatureByRegex).ToArray();
File.WriteAllLines(filename,tempratures); // it creates a new file or overwrites
}
I have to state that above method may be dangerous if input file is too large. Because it reads entire file into memory.
Why don’t you just delete the file before opening the stream writer?
if(File.Exists(filename)){
File.Delete(filename);
}
//here whatever you need to do next
How do i read and sort a text file
sorry if this is an easy question I'm new to coding. I've tried many online solution but none seems to fix my problem:
namespace Login_but_it_hopefully_works
{
public partial class Leaderboard : Form
{
string Line = "";
private string filepath1 = #"Compdetails.txt";
FileStream readerStream = new FileStream("Compdetails.txt", FileMode.Open);
string[] content = null;
public Leaderboard()
{
InitializeComponent();
}
public object ListReadFile { get; private set; }
private void bttn_load_Click(object sender, EventArgs e)
{
string[] content = null;
//Read the content
using (StreamReader CompTXT = File.OpenText(filepath1))
{
content = CompTXT.ReadToEnd().Split(new string[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);
//Remove the entries in the file
readerStream.SetLength(0);
}
FileStream writerStream = new FileStream(#"Desktop\Source\text.txt", FileMode.OpenOrCreate);
using (StreamWriter writer = new StreamWriter(writerStream))
{
//Sort the content and write back to the same file
Array.Sort(content);
writer.Write(string.Join(Environment.NewLine, content));
}
}
}
}
The error is:
Additional information: The process cannot access the file
'E:\CS\Login\Login but it hopefully works\bin\Debug\Compdetails.txt'
because it is being used by another process and the line is " using
(StreamReader CompTXT = File.OpenText(filepath3))"
Remove the 2 lines involving readerStream. They are not accomplishing what do you think they are, but they are causing that error. :-) Your next task will be to overwrite the file rather than append to it.
To elaborate on the cause of the error: having that field declared in the class and initialized by opening a stream causes the file to be locked for as long as an instance of the class exists. When you then call the button event method and try to open another stream with another lock on the same file, an exception results.
i try to write line in file when this exists:
My code is next:
string strRuta = "C:\File.txt"
if (!Directory.Exists(strRuta))
Directory.CreateDirectory(strRuta);
string psContenido = "Hola";
if (!(File.Exists(strRuta + strNombreArchivo)))
{
swArchivo = File.CreateText(strRuta + strNombreArchivo);
}
if (!psContenido.ToLower().Contains("error"))
{
swArchivo.WriteLine(psContenido);
swArchivo.Flush();
swArchivo.Close();
swArchivo.Dispose();
File.SetCreationTime(strRuta + strNombreArchivo, DateTime.Now);
}
but when run this program i have a error in WriteLine, i don´t undertand which is the reason, could you help me?
I would like to know how to write in the file(in the next line the word)
There are a couple of problems, I think. First, you're specifying what looks like a file name and creating a directory with that name (not sure if this is intentional or not). Second, you can use the static helper method AppendAllText of the File class to both create the file if it doesn't exist, and to write the contents to the end of the file. It handles all the streamwriter stuff for you, so you don't have to worry about calling close and dispose.
private static void Main(string[] args)
{
string directory = #"C:\private\temp";
string fileName = "MyFile.txt";
string filePath = Path.Combine(directory, fileName);
string fileContents = "This will be written to the end of the file\r\n";
// This will create the directory if it doesn't exist
Directory.CreateDirectory(directory);
// This will create the file if it doesn't exist, and then write the text at the end.
File.AppendAllText(filePath, fileContents);
File.SetCreationTime(filePath, DateTime.Now);
}
I know this is a bit of a "Day one" question, but I'm still having trouble understanding why my Stream writer is writing empty lines after each time it writes
namespace PostFinder
{
class HistorySaver
{
public static void Save(string item, string path)
{
StreamReader sre = new StreamReader(path);
string historyList = sre.ReadToEnd();
sre.Dispose();
StreamWriter sr = new StreamWriter(path);
sr.WriteLine(historyList+sr.NewLine+item);
sr.Dispose();
}
}
}
sr.WriteLine(historyList+sr.NewLine+item);
The .WriteLine() method puts an end-of-line character after the contents you pass to it. If you don't want that character, use .Write().
It looks like all you are wanting to do is append text to a file, so there is really no need to open a streamreader to read in the existing contents and then write them back out with your new content.
You can use the below to do all that you want in one step. If the input path file doesn't exist it will create a new one, and if it already exists it will just append your new item.
namespace PostFinder
{
class HistorySaver
{
public static void Save(string item, string path)
{
File.AppendAllText(path, item + Environment.NewLine);
}
}
}
I am sending and receiving data using COM port (serial). I have written the following code. This is actually my first C# project as I am kinda new to it. I am trying to write the received data to the text file on my desktop, the program actually creates the file but writes nothing in it. Similarly, I am able to see the received data on the console but it is not being written to the text file. Any help on what I am doing wrong will be much appreciated.
Thank you. The code is below.
class Program
{
SerialPort p = new SerialPort("COM7", 300, Parity.None, 8, StopBits.One);
string sbuffer = string.Empty;
byte i = 0;
static void Main(string[] args)
{
new Program();
}
Program()
{
string[] names = SerialPort.GetPortNames();
Console.WriteLine("Serial ports:");
foreach (string name in names)
{
Console.WriteLine(name);
}
Console.WriteLine("Using COM7");
p.Open();
string data_ = "$1RB\r";
Console.WriteLine("Writing data: {0}",data_);
p.Write(data_);
p.DataReceived += new SerialDataReceivedEventHandler(p_DataReceived);
Console.ReadKey();
p.Close();
}
void p_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
Thread.Sleep(5);
sbuffer += (sender as SerialPort).ReadExisting();
i++;
if (i > 9)
{
Console.WriteLine(sbuffer);
System.IO.File.WriteAllText(#"C:\Users\myname\Desktop\WriteText.txt", sbuffer);
sbuffer = string.Empty;
}
}
}
}
You could use events, or simply use this method and pass your data string to it. It will simply append to the file as long as it exists, or create a new file if it does not. The data written should be identical to whatever output is appearing in your console screen.
static void WriteOutputToTextFile(string _data)
{
string FolderName = Environment.GetFolderPath(Environment.SpecialFolder.Desktop); //set destination as your desktop
using (StreamWriter SW = new StreamWriter(FolderName + "\\test.txt", true)) //true makes it append to the file instead of overwrite
{
SW.WriteLine(_data);
SW.Close();
}
}
You are opening and overwriting the same file again and again. Use the FileStream (or even better, StreamWriter) class instead, keep the stream open together with the serial port and close it when you're done.
Also, if you transmit text via the serial port, you might want to consider the SerialPort.ReadLine() method that is much easier to use.
Extending #Alan's answer, you can use File.AppendAllText instead of File.WriteAllText which will overwrite the file again and again. So if you receive empty text before you check the file, the file will be overwritten with empty text.