Develop Reference

C# Streamwriter - Problem with the encoding

I have some product data that I want to write into a csv file. First I have a function that writes the header into the csv file:
using(StreamWriter streamWriter = new StreamWriter(path))
{
string[] headerContent = {"banana","apple","orange"};
string header = string.Join(",", headerContent);
streamWriter.WriteLine(header);
}
Another function goes over the products and writes their data into the csv file:
using (StreamWriter streamWriter = new StreamWriter(new FileStream(path, FileMode.Open), Encoding.UTF8))
{
foreach (var product in products)
{
await streamWriter.WriteLineAsync(product.ToString());
}
}
When writing the products into the csv file and do it with FileMode.Open and Encoding.UTF8, the encoding is set correctly into the file meaning that special characters in german or french get shown correctly. But the problem here is that I overwrite my header when I do it like this.
The solution I tried was to not use FileMode.Open but to use FileMode.Append which works, but then for some reason the encoding just gets ignored.
What could I do to append the data while maintaing the encoding? And also why is this happening in the first place?
EDIT:
Example with FileMode.Open:
Fußpflegecreme
Example with FileMode.Append:
Fußpflegecreme

The important question here is: what does the file actually contain; for example, if I use the following:
using System.Text;
string path = "my.txt";
using (StreamWriter streamWriter = new StreamWriter(new FileStream(path, FileMode.Create), Encoding.UTF8))
{
streamWriter.WriteLine("Fußpflegecreme 1");
}
using (StreamWriter streamWriter = new StreamWriter(new FileStream(path, FileMode.Append), Encoding.UTF8))
{
streamWriter.WriteLine("Fußpflegecreme 2");
}
// this next line is lazy and inefficient; only good for quick tests
Console.WriteLine(BitConverter.ToString(File.ReadAllBytes(path)));
then the output is (re-formatted a little):
EF-BB-BF-
46-75-C3-9F-70-66-6C-65-67-65-63-72-65-6D-65-20-31-0D-0A-
46-75-C3-9F-70-66-6C-65-67-65-63-72-65-6D-65-20-32-0D-0A
The first line (note: there aren't any "lines" in the original hex) is the UTF-8 BOM; the second and third lines are the correctly UTF-8 encoded payloads. It would help if you could show the exact bytes that get written in your case. I wonder if the real problem here is that in your version, there is no BOM, but the rest of the data is correct. Some tools, in the absence of a BOM, will choose the wrong encoding. But also, some tools: in the presence of a BOM: will incorrectly show some garbage at the start of the file (and may also, because they're clearly not using the BOM: use the wrong encoding). The preferred option is: specify the encoding explicitly when reading the file, and use a tool that can handle the presence of absence of a BOM.
Whether or not to include a BOM (especially in the case of UTF-8) is a complex question, and there are pros/cons of each - and there are tools that will work better, or worse, with each. A lot of UTF-8 text files do not include a BOM, but: there is no universal answer. The actual content is still correctly UTF-8 encoded whether or not there is a BOM - but how that is interpreted (in either case) is up to the specific tool that you're using to read the data (and how that tool is configured).

I think this will be solved once you explicitly choose the utf8 encoding when writing the header. This will prefix the file with a BOM.

How to set the BOM for a file being read

I have been having issues reading a file that contains a mix of Arabic and Western text. I read the file into a TextBox as follows:
tbx1.Text = File.ReadAllText(fileName.Text, Encoding.UTF8);
No matter what value I tried instead of "Encoding.UTF8" I got garbled characters displayed in place of the Arabic. The western text was displayed fine.
I thought it might have been an issue with the way the TextBox was defined, but on start up I write some mixed Western/Arabic text to the textbox and this displays fine:
tbx1.Text = "Start السلا عليكم" + Environment.NewLine + "Here";
Then I opened Notepad and copied the above text into it, then saved the file, at which point Notepad save dialogue asked for which encoding to use.
I then presented the saved file to my code and it displayed all the content correctly.
I examined the file and found 3 binary bytes at the beginning (not visible in Notepad):
The 3 bytes, I subsequently found through research represent the BOM, and this enables the C# "File.ReadAllText(fileName.Text, Encoding.UTF8);" to read/display the data as desired.
What puzzles me is specifying the " Encoding.UTF8" value should take care of this.
The only way I can think is to code up a step to add this data to a copy of teh file, then process that file. But this seems rather long-winded. Just wondering if there is a better way to do, or why the Encoding.UTF8 is not yielding the desired result.
Edit:
Still no luck despite trying the suggestion in the answer.
I cut the test data down to containing just Arabic as follows:
Code as follows:
FileStream fs = new FileStream(fileName.Text, FileMode.Open);
StreamReader sr = new StreamReader(fs, Encoding.UTF8, false);
tbx1.Text = sr.ReadToEnd();
sr.Close();
fs.Close();
Tried with both "true" and "false" on the 2nd line, but both give the same result.
If I open the file in Notepad++, and specify the Arabic ISO-8859-6 Character set it displays fine.
Here is what is looks like in Notepad++ (and what I would liek the textbox to display):
Not sure if the issue is in the reading from file, or the writing to the textbox.
I will try inspecting the data post read to see. But at the moment, I'm puzzled.

The StreamReader class has a constructor that will take care of testing for the BOM for you:
using (var stream = new FileStream(fileName.Text, FileAccess.Read))
{
using (var sr = new StreamReader(stream, Encoding.UTF8, true))
{
var text = sr.ReadToEnd();
}
}
The final true parameter is detectEncodingFromByteOrderMark:
The detectEncodingFromByteOrderMarks parameter detects the encoding by looking at the first three bytes of the stream. It automatically recognizes:
UTF-8
little-endian Unicode
and big-endian Unicode text
if the file
starts with the appropriate byte order marks. Otherwise, the
user-provided encoding is used. See the Encoding.GetPreamble method
for more information.

C# StreamReader/StreamWriter encoding oddity

I have a very simple c# console app that reads through a text file and outputs the same file but with a particular string replaced on each line that it appears - utilizing StreamReader and StreamWriter. I do not know the encoding of the source file. I have encountered a situation where there is a character in the file (ext ascii dec 166, broken pipe) that when running through this app gets "mangled" using the default encoding (In the output file it ends up as a "box" character). Since I do not know the source file encoding I have attempted multiple options to see what would provide an unaltered result and oddly the only way that works is having it read in UTF-7 and written in UTF-8.
UTF-7 to UTF-7 causes problems like & to change to +AC. UTF-8 to UTF-8 (which I believe is the default) converts the character in question to the "box". ASCII to ASCII turns it into ?. Unicode to Unicode results in gibberish. Shouldn't it be same encoding read and write for same results? Simplified code example below:
using (var fileStream = new FileStream(fileName, FileMode.Open))
using (var fileReader = new StreamReader(fileStream,Encoding.UTF7))
using (var fileStreamOut = new FileStream(tempFileName,FileMode.Create))
using (var fileWriter = new StreamWriter(fileStreamOut,Encoding.UTF8))
{
while (!fileReader.EndOfStream)
{
var inputLine = fileReader.ReadLine();
if (inputLine != null)
{
inputLine = inputLine.Substring(0, 3) + newRdfi + inputLine.Substring(12);
fileWriter.WriteLine(inputLine);
}
}
fileWriter.Flush();
}

After clarification on the file creation method received from the developer of the source system and knowledge of the server it is being produced on I came to the conclusion the encoding was Windows-1252. Changing my read and write streams to use Encoding.GetEncoding(1252) resulted in all characters reading and outputting as expected.

How to set a file's encoding when writing it out in c#?

I'm not full certain I understand file encoding completely. If I write out text to a file in c#, how can I set the encoding type of that file? Maybe it's just I do not understand the full spectrum of file encoding.
using (var sw = new StreamWriter(File.Open(#"c:\test.txt", FileMode.CreateNew), Encoding.GetEncoding("iso-8859-1")))
{
sw.WriteLine("my text...");
}

Your code does exactly that - you're writing out text using ISO Latin 1.
Note that there's nothing in the file itself to specify the encoding, unless you're writing out a file which allows you to specify that. The file is basically just a sequence of bytes. The encoding you're specifying in your code determines how the text you're writing is converted into bytes, that's all.

Use the constructor that accepts an Encoding parameter, which you already do, and set the encoding to the one you like.

Something like this
using (var sw = new StreamWriter(fileName, true, System.Text.Encoding.UTF8,512);
{
sw.WriteLine(""text here);
}

C# Help reading foreign characters using StreamReader

I'm using the code below to read a text file that contains foreign characters, the file is encoded ANSI and looks fine in notepad. The code below doesn't work, when the file values are read and shown in the datagrid the characters appear as squares, could there be another problem elsewhere?
StreamReader reader = new StreamReader(inputFilePath, System.Text.Encoding.ANSI);
using (reader = File.OpenText(inputFilePath))
Thanks
Update 1: I have tried all encodings found under System.Text.Encoding. and all fail to show the file correctly.
Update 2: I've changed the file encoding (resaved the file) to unicode and used System.Text.Encoding.Unicode and it worked just fine. So why did notepad read it correctly? And why didn't System.Text.Encoding.Unicode read the ANSI file?

You may also try the Default encoding, which uses the current system's ANSI codepage.
StreamReader reader = new StreamReader(inputFilePath, Encoding.Default, true)
When you try using the Notepad "Save As" menu with the original file, look at the encoding combo box. It will tell you which encoding notepad guessed is used by the file.
Also, if it is an ANSI file, the detectEncodingFromByteOrderMarks parameter will probably not help much.

I had the same problem and my solution was simple: instead of
Encoding.ASCII
use
Encoding.GetEncoding("iso-8859-1")
The answer was found here.
Edit: more solutions. This maybe more accurate one:
Encoding.GetEncoding(1252);
Also, in some cases this will work for you too if your OS default encoding matches file encoding:
Encoding.Default;

Yes, it could be with the actual encoding of the file, probably unicode. Try UTF-8 as that is the most common form of unicode encoding. Otherwise if the file ASCII then standard ASCII encoding should work.

Using Encoding.Unicode won't accurately decode an ANSI file in the same way that a JPEG decoder won't understand a GIF file.
I'm surprised that Encoding.Default didn't work for the ANSI file if it really was ANSI - if you ever find out exactly which code page Notepad was using, you could use Encoding.GetEncoding(int).
In general, where possible I'd recommend using UTF-8.

Try a different encoding such as Encoding.UTF8. You can also try letting StreamReader find the encoding itself:
StreamReader reader = new StreamReader(inputFilePath, System.Text.Encoding.UTF8, true)
Edit: Just saw your update. Try letting StreamReader do the guessing.

For swedish Å Ä Ö the only solution form the ones above working was:
Encoding.GetEncoding("iso-8859-1")
Hopefully this will save someone time.

File.OpenText() always uses an UTF-8 StreamReader implicitly. Create your own StreamReader
instance instead and specify the desired encoding.
like
using (StreamReader reader = new StreamReader(#"C:\test.txt", Encoding.Default)
{
// ...
}

I solved my problem of reading portuguese characters, changing the source file on notepad++.
C#
var url = System.Web.HttpContext.Current.Server.MapPath(#"~/Content/data.json");
string s = string.Empty;
using (System.IO.StreamReader sr = new System.IO.StreamReader(url, System.Text.Encoding.UTF8,true))
{
s = sr.ReadToEnd();
}

I'm also reading an exported file which contains french and German languages. I used Encoding.GetEncoding("iso-8859-1"), true which worked out without any challenges.

for Arabic, I used Encoding.GetEncoding(1256). it is working good.

I had a similar problem with ProcessStartInfo and the property StandardOutputEncoding. I set it for German language console output to code page 850. This way I could read the output like ausführen instead of ausf�hren.