Create and write to a text file inmemory and convert to byte array in one go

Question

How can I create a .csv file implicitly/automatically by using the correct method, add text to that file existing in memory and then convert to in memory data to a byte array?

string path = @"C:\test.txt";
File.WriteAllLines(path, GetLines());
byte[] bytes = System.IO.File.ReadAllBytes(path);

With that approach I create a file always (good), write into it (good) then close it (bad) then open the file again from a path and read it from the hard disc (bad)

How can I improve that?

UPDATE

One nearly good approach would be:

  using (var fs = new FileStream(@"C:\test.csv", FileMode.Create, FileAccess.ReadWrite))
            {

                using (var memoryStream = new MemoryStream())
                {

                    fs.CopyTo(memoryStream );
                    return memoryStream .ToArray();
                }

        }

but I am not able to write text into that filestream... just bytes...

UPDATE 2

 using (var fs = File.Create(@"C:\temp\test.csv"))
            {
                using (var sw = new StreamWriter(fs, Encoding.Default))
                {
                    using (var ms = new MemoryStream())
                    {
                        String message = "Message is the correct ääüö Pi(\u03a0), and Sigma (\u03a3).";
                        sw.Write(message);
                        sw.Flush();
                        fs.CopyTo(ms);
                        return ms.ToArray();
                    }
                }
            }

The string message is not persisted to the test.csv file. Anyone knows why?

Xilmiki · Accepted Answer · 2022-02-01T13:53:05.373

42

Write text into Memory Stream.

byte[] bytes = null;
using (var ms = new MemoryStream())
{
    using(TextWriter tw = new StreamWriter(ms)){
       tw.Write("blabla");
       tw.Flush();
       ms.Position = 0;
       bytes = ms.ToArray();
    }
  
}

UPDATE

Use file stream Directly and write to File

using (var fs = new FileStream(@"C:\ed\test.csv", FileMode.Create, FileAccess.ReadWrite))
{
    using (TextWriter tw = new StreamWriter(fs))
    {
        tw.Write("blabla");
        tw.Flush();
    }
}

edited Feb 01 '22 at 13:53

answered Apr 16 '16 at 07:20

Xilmiki

1,453
15
22

how do you pass the TextWriter to the FileStream? Creating a FileStream you can not pass that. – HelloWorld Apr 16 '16 at 07:30
TextWriter accept a stream as input so you can use FileStream directly on it. – Xilmiki Apr 16 '16 at 07:35
I think you misunderstand my original question. I do not just want to create a text file... please consider also the byte[] with the "text" data I want. – HelloWorld Apr 16 '16 at 07:36
merge my answer with your first update,I think it will work – Xilmiki Apr 16 '16 at 07:50
You have any idea why UPDATE 2 does not write anything into my file? – HelloWorld Apr 16 '16 at 08:14
So you tested my code of UPDATE2 and it worked really? – HelloWorld Apr 16 '16 at 08:41
Oh... I looked in the wrong DIRectory. Yes its written into that file, but the byte[] returned to the user in the browser which results in a file if download is EMPTY. That wonders me... – HelloWorld Apr 16 '16 at 08:49
What is point of `ms.WriteTo(ms);` ? – Masoud Keshavarz Jan 30 '22 at 07:32
@MasoudKeshavarz Was a bad edit by admin (removed) – Xilmiki Feb 01 '22 at 13:55

score 18 · Answer 2 · edited Sep 05 '21 at 13:02

18

You can get a byte array from a string using encoding:

Encoding.ASCII.GetBytes(aString);

Or

Encoding.UTF8.GetBytes(aString);

But I don't know why you would want a csv as bytes. You could load the entire file to a string, add to it and then save it:

string content;

using (var reader = new StreamReader(filename))
{
    content = reader.ReadToEnd();
}

content += "x,y,z";

using (var writer = new StreamWriter(filename))
{
    writer.Write(content);
}

Update: Create a csv in memory and pass back as bytes:

var stringBuilder = new StringBuilder();
foreach(var line in GetLines())
{
    stringBuilder.AppendLine(line);
}
return Encoding.ASCII.GetBytes(stringBuilder.ToString());

edited Sep 05 '21 at 13:02

Alex

14,104
11
54
77

answered Apr 16 '16 at 08:05

Steve Harris

5,014
1
10
25

I want a .csv file as bytes returning them from a HttpGet request as a file for the user. – HelloWorld Apr 16 '16 at 08:07
Do you actually want a csv file to be created on disk, or just the bytes to pass back? – Steve Harris Apr 16 '16 at 08:11
Return byte[] is enough - if thats possible - – HelloWorld Apr 16 '16 at 08:14
Although ASCII has the chars 'ö', 'Ä' which are german. Still my excel or notepadd++ did display them as '?????' string. Is that a problem of those apps? When I use UTF8 it works. – HelloWorld Apr 16 '16 at 08:46
If you're using those chars then utf8 is better. Ascii is not really suitable for that. – Steve Harris Apr 16 '16 at 09:24

Create and write to a text file inmemory and convert to byte array in one go

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