CODEWITHSUNDEEP
c#text-files
Berker Yüceer
Berker Yüceer

Reputation: 7335

Create a .txt file if doesn't exist, and if it does append a new line

I would like to create a .txt file and write to it, and if the file already exists I just want to append some more lines:

string path = @"E:\AppServ\Example.txt";
if (!File.Exists(path))
{
    File.Create(path);
    TextWriter tw = new StreamWriter(path);
    tw.WriteLine("The very first line!");
    tw.Close();
}
else if (File.Exists(path))
{
    TextWriter tw = new StreamWriter(path);
    tw.WriteLine("The next line!");
    tw.Close(); 
}

But the first line seems to always get overwritten... how can I avoid writing on the same line (I'm using this in a loop)?

I know it's a pretty simple thing, but I never used the WriteLine method before. I'm totally new to C#.

Upvotes: 191

Views: 539981

Answers (15)

Daniel Hilgarth
Daniel Hilgarth

Reputation: 174329

Use the correct constructor:

else if (File.Exists(path))
{
    using(var sw = new StreamWriter(path, true))
    {
        sw.WriteLine("The next line!");
    }
}

Upvotes: 199

Jaideep Dhumal
Jaideep Dhumal

Reputation: 1047

Please note that AppendAllLines and AppendAllText methods only create the file, but not the path. So if you are trying to create a file in "C:\Folder", please ensure that this path exists.

Upvotes: 0

R M Shahidul Islam Shahed
R M Shahidul Islam Shahed

Reputation: 1346

.NET Core Console App:

public static string RootDir() => Path.GetFullPath(Path.Combine(AppContext.BaseDirectory, @"..\..\..\"));


string _OutputPath = RootDir() + "\\Output\\" + "MyFile.txt";
if (!File.Exists(_OutputPath))
    File.Create(_OutputPath).Dispose();
using (TextWriter _StreamWriter = new StreamWriter(_OutputPath))
{
    _StreamWriter.WriteLine(strOriginalText);
}

Upvotes: 0

Vijay Shaaruck
Vijay Shaaruck

Reputation: 692

You can just use File.AppendAllText() Method this will solve your problem. This method will take care of File Creation if not available, opening and closing the file.

var outputPath = @"E:\Example.txt";
var data = "Example Data";
File.AppendAllText(outputPath, data);

Upvotes: 5

Asiri Jayaweera
Asiri Jayaweera

Reputation: 357

Try this.

string path = @"E:\AppServ\Example.txt";
if (!File.Exists(path))
{
    using (var txtFile = File.AppendText(path))
    {
        txtFile.WriteLine("The very first line!");
    }
}
else if (File.Exists(path))
{     
    using (var txtFile = File.AppendText(path))
    {
        txtFile.WriteLine("The next line!");
    }
}

Upvotes: 3

Aek
Aek

Reputation: 499

string path=@"E:\AppServ\Example.txt";

if(!File.Exists(path))
{
   File.Create(path).Dispose();

   using( TextWriter tw = new StreamWriter(path))
   {
      tw.WriteLine("The very first line!");
   }

}    
else if (File.Exists(path))
{
   using(TextWriter tw = new StreamWriter(path))
   {
      tw.WriteLine("The next line!");
   }
}

Upvotes: 48

Andreas Gusakov
Andreas Gusakov

Reputation: 73

using(var tw = new StreamWriter(path, File.Exists(path)))
{
    tw.WriteLine(message);
}

Upvotes: 1

dubucha
dubucha

Reputation: 1057

File.AppendAllText adds a string to a file. It also creates a text file if the file does not exist. If you don't need to read content, it's very efficient. The use case is logging.

File.AppendAllText("C:\\log.txt", "hello world\n");

Upvotes: 16

David Fawzy
David Fawzy

Reputation: 1076

From microsoft documentation, you can create file if not exist and append to it in a single call File.AppendAllText Method (String, String)

.NET Framework (current version) Other Versions

Opens a file, appends the specified string to the file, and then closes the file. If the file does not exist, this method creates a file, writes the specified string to the file, then closes the file. Namespace: System.IO Assembly: mscorlib (in mscorlib.dll)

Syntax C#C++F#VB public static void AppendAllText( string path, string contents ) Parameters path Type: System.String The file to append the specified string to. contents Type: System.String The string to append to the file.

AppendAllText

Upvotes: 1

John Boling
John Boling

Reputation: 463

You don't actually have to check if the file exists, as StreamWriter will do that for you. If you open it in append-mode, the file will be created if it does not exists, then you will always append and never over write. So your initial check is redundant.

TextWriter tw = new StreamWriter(path, true);
tw.WriteLine("The next line!");
tw.Close();

Upvotes: 25

drch
drch

Reputation: 3070

string path = @"E:\AppServ\Example.txt";
File.AppendAllLines(path, new [] { "The very first line!" });

See also File.AppendAllText(). AppendAllLines will add a newline to each line without having to put it there yourself.

Both methods will create the file if it doesn't exist so you don't have to.

Upvotes: 72

Smack
Smack

Reputation: 946

 else if (File.Exists(path)) 
{ 
  using (StreamWriter w = File.AppendText(path))
        {
            w.WriteLine("The next line!"); 
            w.Close();
        }
 }

Upvotes: 3

Matan Shahar
Matan Shahar

Reputation: 3240

When you start StreamWriter it's override the text was there before. You can use append property like so:

TextWriter t = new StreamWriter(path, true);

Upvotes: 3

Tom Ceuppens
Tom Ceuppens

Reputation: 396

You could use a FileStream. This does all the work for you.

http://www.csharp-examples.net/filestream-open-file/

Upvotes: 2

Ed Manet
Ed Manet

Reputation: 3178

You just want to open the file in "append" mode.

http://msdn.microsoft.com/en-us/library/3zc0w663.aspx

Upvotes: 6

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