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How to write to an existing txt file c# [duplicate]

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Open existing file, append a single line
(9 answers)
Closed 4 years ago.
I have created some code which creates a txt file with an initial text, however when I try to call the method again with a new msg it does not add it to the txt file. Below is my code:
string example = "test";
WriteToLgo(example);
public static void WriteToLog(String inputtext)
{
string location= #"C:\Users\";
string NameOfFile = "test.txt";
string fileName= String.Format("{0:yyyy-MM-dd}__{1}", DateTime.Now, NameOfFile);
string path= Path.Combine(location, fileName);
using (StreamWriter sr= File.CreateText(path))
{
sr.WriteLine(inputtext);
}
}
If I try and call the method a second time the new msg does not get added. Any help will be appreciated.

You should not use File.CreateText, but this StreamWriter overload instead:
//using append = true
using (StreamWriter sr = new StreamWriter(path, true))
{
sr.WriteLine(inputtext);
}
See MSDN

The File.CreateText only creates a new file each time, overwriting anything in it. Does not append to existing files.
You should use either File.AppendText(...) to open your existing file for appending content, or use the base StreamWriter class to open it with append options
Something like:
using (StreamWriter sr = File.AppendText(path))
{
sr.WriteLine(inputtext);
}
If you use the base StreamWriter class instead of File.AppendText you can use it like StreamWriter sr = new StreamWriter(path, true); HOWEVER, you must check to see if the file exists before open it for append. Probably reccomend the File.AppendText in your case.

Streamwriter is clearing the text from my text file then updating

I'm trying to get my streamwriter to add text onto the end of the text file but for some reason, it is just replacing the text with whatever I have entered. Any help is appreciated to fix this.
StreamWriter sw = new StreamWriter(Server.MapPath("~") + "/App_Data/blogMessages.txt");
sw.WriteLine(postTextBox.Text);
sw.Close();

you can use a over ridden method for stream writer
StreamWriter sw = new StreamWriter(Server.MapPath("~") + "/App_Data/blogMessages.txt", true);
this will apppend your text

You need to use the overload version of the StreamWriter constructor that take an extra parameter to configure overwrite or append to the stream. And please add the using statement
using(StreamWriter sw = new StreamWriter(Server.MapPath("~") +
"/App_Data/blogMessages.txt", true))
{
sw.WriteLine(postTextBox.Text);
}
The using statement allows for the correct close and dispose of the stream also in case you get an exception when opening or writing

try this
using (System.IO.TextWriter tw = new System.IO.StreamWriter(#"D:\TEMP\IEALog\path.txt", true))
{
tw.WriteLine(message + "Source ;- " + source + "StackTrace:- " + exc.StackTrace.ToString());
}

Append lines to a file using a StreamWriter

I want to append lines to my file. I am using a StreamWriter:
StreamWriter file2 = new StreamWriter(#"c:\file.txt");
file2.WriteLine(someString);
file2.Close();
The output of my file should be several strings below each other, but I have only one row, which is overwritten every time I run this code.
Is there some way to let the StreamWriter append to an existing file?

Use this instead:
new StreamWriter("c:\\file.txt", true);
With this overload of the StreamWriter constructor you choose if you append the file, or overwrite it.
C# 4 and above offers the following syntax, which some find more readable:
new StreamWriter("c:\\file.txt", append: true);

using (FileStream fs = new FileStream(fileName,FileMode.Append, FileAccess.Write))
using (StreamWriter sw = new StreamWriter(fs))
{
sw.WriteLine(something);
}

I assume you are executing all of the above code each time you write something to the file. Each time the stream for the file is opened, its seek pointer is positioned at the beginning so all writes end up overwriting what was there before.
You can solve the problem in two ways: either with the convenient
file2 = new StreamWriter("c:/file.txt", true);
or by explicitly repositioning the stream pointer yourself:
file2 = new StreamWriter("c:/file.txt");
file2.BaseStream.Seek(0, SeekOrigin.End);

Try this:
StreamWriter file2 = new StreamWriter(#"c:\file.txt", true);
file2.WriteLine(someString);
file2.Close();

Replace this:
StreamWriter file2 = new StreamWriter("c:/file.txt");
with this:
StreamWriter file2 = new StreamWriter("c:/file.txt", true);
true indicates that it appends text.

Actually only Jon's answer (Sep 5 '11 at 9:37) with BaseStream.Seek worked for my case. Thanks Jon! I needed to append lines to a zip archived txt file.
using (FileStream zipFS = new FileStream(#"c:\Temp\SFImport\test.zip",FileMode.OpenOrCreate))
{
using (ZipArchive arch = new ZipArchive(zipFS,ZipArchiveMode.Update))
{
ZipArchiveEntry entry = arch.GetEntry("testfile.txt");
if (entry == null)
{
entry = arch.CreateEntry("testfile.txt");
}
using (StreamWriter sw = new StreamWriter(entry.Open()))
{
sw.BaseStream.Seek(0,SeekOrigin.End);
sw.WriteLine("text content");
}
}
}

Use this StreamWriter constructor with 2nd parameter - true.

Another option is using System.IO.File.AppendText
This is equivalent to the StreamWriter overloads others have given.
Also File.AppendAllText may give a slightly easier interface without having to worry about opening and closing the stream. Though you may need to then worry about putting in your own linebreaks. :)

One more simple way is using the File.AppendText it appends UTF-8 encoded text to an existing file, or to a new file if the specified file does not exist and returns a System.IO.StreamWriter
using (System.IO.StreamWriter sw = System.IO.File.AppendText(logFilePath + "log.txt"))
{
sw.WriteLine("this is a log");
}

Replace this line:
StreamWriter sw = new StreamWriter("c:/file.txt");
with this code:
StreamWriter sw = File.AppendText("c:/file.txt");
and then write your line to the text file like this:
sw.WriteLine("text content");

You can use like this
using (System.IO.StreamWriter file =new System.IO.StreamWriter(FilePath,true))
{
`file.Write("SOme Text TO Write" + Environment.NewLine);
}

Clearing content of text file using C#

How can I clear the content of a text file using C# ?

File.WriteAllText(path, String.Empty);
Alternatively,
File.Create(path).Close();

Just open the file with the FileMode.Truncate flag, then close it:
using (var fs = new FileStream(#"C:\path\to\file", FileMode.Truncate))
{
}

using (FileStream fs = File.Create(path))
{
}
Will create or overwrite a file.

You can clear contents of a file just like writing contents in the file but replacing the texts with ""
File.WriteAllText(#"FilePath", "");

Another short version:
System.IO.File.WriteAllBytes(path, new byte[0]);

Simply write to file string.Empty, when append is set to false in StreamWriter. I think this one is easiest to understand for beginner.
private void ClearFile()
{
if (!File.Exists("TextFile.txt"))
File.Create("TextFile.txt");
TextWriter tw = new StreamWriter("TextFile.txt", false);
tw.Write(string.Empty);
tw.Close();
}

You can use always stream writer.It will erase old data and append new one each time.
using (StreamWriter sw = new StreamWriter(filePath))
{
getNumberOfControls(frm1,sw);
}

StreamWriter not writing to an existing file

I am trying to write some text to the file using StreamWriter and getting the
path for the file from FolderDialog selected folder. My code works fine if the
file does not already exist. but if the file already exist it throws the Exception
that the file is in used by other process.
using(StreamWriter sw = new StreamWriter(FolderDialog.SelectedPath + #"\my_file.txt")
{
sw.writeLine("blablabla");
}
Now if I write like this:
using(StreamWriter sw = new StreamWriter(#"C:\some_folder\my_file.txt")
it works fine with an existing file.

It may have to do with the way you are combining your path and filename. Give this a try:
using(StreamWriter sw = new StreamWriter(
Path.Combine(FolderDialog.SelectedPath, "my_file.txt"))
{
sw.writeLine("blablabla");
}
Also, check to make sure the FolderDialog.SelectedPath value isn't blank. :)

The file is already in use, so it cannot be overwritten. However, note that this message isn't always entirely accurate - the file may in fact be in use by your own process. Check your usage patterns.

This is a cheap answer, but have you tried this workaround?
string sFileName= FolderDialog.SelectedPath + #"\my_file.txt";
using(StreamWriter sw = new StreamWriter(sFileName))
{
sw.writeLine("blablabla");
}
The other thing I would suggest is verifying that FolderDialog.SelectedPath + "\my_file.txt" is equal to the hard coded path of "C:\some_folder\my_file.txt".

Check whether the file is in fact in use by some other process.
To do that, run Process Explorer, press Ctrl+F, type the filename, and click Find.
As an aside, the best way to accomplish this task is like this:
using(StreamWriter sw = File.AppendText(Path.Combine(FolderDialog.SelectedPath, #"my_file.txt")))
EDIT: Do NOT put a slash in the second argument to Path.Combine.

Try this
using (StreamWriter sw = File.AppendText(#"C:\some_folder\my_file.txt"))
{
sw.writeLine("blablabla");
}
it will only work in existing file, so to validate if the file is new or already exists, do something like
string path = #"C:\some_folder\my_file.txt";
if (!File.Exists(path))
{
// Create a file to write to.
using (StreamWriter sw = File.CreateText(path))
{
//once file was created insert the text or the columns
sw.WriteLine("blbalbala");
}
}
// if already exists just write
using (StreamWriter sw = File.AppendText(#"C:\some_folder\my_file.txt"))
{
sw.writeLine("blablabla");
}