Csharp/CSharp Tutorial/File Directory Stream/Text File Read Write

Create a file called test.txt in the current directory:

using System;
using System.IO;
class Program {
    static void Main() {
        using (Stream s = new FileStream("test.txt", FileMode.Create)) {
            Console.WriteLine(s.CanRead);       // true
            Console.WriteLine(s.CanWrite);      // true
            Console.WriteLine(s.CanSeek);       // true
            s.WriteByte(101);
            s.WriteByte(102);
            byte[] block = { 1, 2, 3, 4, 5 };
            s.Write(block, 0, block.Length);     // Write block of 5 bytes
            Console.WriteLine(s.Length);         // 7
            Console.WriteLine(s.Position);       // 7
            s.Position = 0;                       // Move back to the start
            Console.WriteLine(s.ReadByte());     // 101
            Console.WriteLine(s.ReadByte());     // 102
            Console.WriteLine(s.Read(block, 0, block.Length));   // 5
            Console.WriteLine(s.Read(block, 0, block.Length));   // 0
        }
    }
}

Display a text file.

using System; 
using System.IO;  
 
class MainClass { 
  public static void Main(string[] args) { 
    int i; 
    FileStream fin; 
 
    try { 
      fin = new FileStream("test.txt", FileMode.Open); 
    } catch(FileNotFoundException exc) { 
      Console.WriteLine(exc.Message); 
      return; 
    } catch(IndexOutOfRangeException exc) { 
      Console.WriteLine(exc.Message + "\nUsage: ShowFile File"); 
      return; 
    } 
 
    // read bytes until EOF is encountered 
    do { 
      try { 
        i = fin.ReadByte(); 
      } catch(Exception exc) { 
        Console.WriteLine(exc.Message); 
        return; 
      } 
      if(i != -1) Console.Write((char) i); 
    } while(i != -1); 
 
    fin.Close(); 
  } 
}

Get interal StringBuilder from a StringWriter

using System;
using System.IO;
using System.Text;
public class MainClass
{
    public static int Main(string[] args)
    {
    // Get a StringWriter and write some stuff.
    StringWriter writer = new StringWriter();
    writer.WriteLine("string 1");
    
    for(int i = 0; i < 10; i++)
    {
      writer.Write(i + " ");
    }
    writer.Write(writer.NewLine);
    writer.Close();
    Console.WriteLine("Contents:\n{0}", writer);
    
    StringBuilder str = writer.GetStringBuilder();
    string allOfTheData = str.ToString();
    Console.WriteLine("-> StringBuilder says:\n{0}", allOfTheData);
    str.Insert(20, "INSERTED STUFF");
    allOfTheData = str.ToString();
    Console.WriteLine("-> New StringBuilder says:\n{0}", allOfTheData);
    StringReader sr = new StringReader(writer.ToString());
    
    string input = null;
    while ((input = sr.ReadLine()) != null)
    {
      Console.WriteLine (input);
    }
    sr.Close();
        return 0;
    }
}

Contents:
string 1
0 1 2 3 4 5 6 7 8 9
-> StringBuilder says:
string 1
0 1 2 3 4 5 6 7 8 9
-> New StringBuilder says:
string 1
0 1 2 3 4 INSERTED STUFF5 6 7 8 9
string 1
0 1 2 3 4 INSERTED STUFF5 6 7 8 9

Reading Writing To Text File

using System;
using System.IO;
    class Tester
    {
        public static void Main()
        {
            FileInfo theSourceFile = new FileInfo("test.cs");
            StreamReader reader = theSourceFile.OpenText();
            StreamWriter writer = new StreamWriter("test.bak", false);
            string text;
            do
            {
                text = reader.ReadLine();
                writer.WriteLine(text);
                Console.WriteLine(text);
            } while (text != null);
            reader.Close();
            writer.Close();
        }
    }

Read text file line by line

using System;
using System.IO;
class MainClass
{
  public static void Main() 
  {
    FileStream outStream = File.Create("c:\\Test.txt");
    StreamWriter sw = new StreamWriter(outStream);
    sw.WriteLine("This is a test of the StreamWriter class");
    sw.Flush();
    sw.Close();
    StreamReader sr = new StreamReader("c:\\Test.txt");
    string FirstLine;
  
    FirstLine = sr.ReadLine();
    Console.WriteLine(FirstLine);
    sr.Close();
  }
}

Read/Write text file using the StringWriter

using System;
using System.IO;
using System.Text;
public class MainClass
{
    public static int Main(string[] args)
    {
    // Get a StringWriter and write some stuff.
    StringWriter writer = new StringWriter();
    writer.WriteLine("string 1");
    
    for(int i = 0; i < 10; i++)
    {
      writer.Write(i + " ");
    }
    writer.Write(writer.NewLine);
    writer.Close();
    Console.WriteLine("Contents:\n{0}", writer);
    
    StringBuilder str = writer.GetStringBuilder();
    string allOfTheData = str.ToString();
    Console.WriteLine("-> StringBuilder says:\n{0}", allOfTheData);
    str.Insert(20, "INSERTED STUFF");
    allOfTheData = str.ToString();
    Console.WriteLine("-> New StringBuilder says:\n{0}", allOfTheData);
    StringReader sr = new StringReader(writer.ToString());
    
    string input = null;
    while ((input = sr.ReadLine()) != null)
    {
      Console.WriteLine (input);
    }
    sr.Close();
        return 0;
    }
}

Contents:
string 1
0 1 2 3 4 5 6 7 8 9
-> StringBuilder says:
string 1
0 1 2 3 4 5 6 7 8 9
-> New StringBuilder says:
string 1
0 1 2 3 4 INSERTED STUFF5 6 7 8 9
string 1
0 1 2 3 4 INSERTED STUFF5 6 7 8 9

Simple IO with the File Type

using System;
using System.IO;
class Program
{
  static void Main(string[] args)
  {
    string[] myTasks = {"A", "C","C", "P"};
    File.WriteAllLines(@"C:\tasks.txt", myTasks);
    foreach (string task in File.ReadAllLines(@"C:\tasks.txt"))
    {
      Console.WriteLine("TODO: {0}", task);
    }
  }
}

Use while loop to read a text file

using System;
using System.IO;
class MainClass
{
  public static void Main(string[] args)
  {
    try
    {
      StreamReader sr = File.OpenText("c:\\boot.ini");
      string strLine;
      while(null != (strLine = sr.ReadLine()))
      {
        Console.WriteLine(strLine);
      }
      sr.Close();
    }
    catch(FileNotFoundException e)
    {
      Console.WriteLine(e.Message);
    }
  }
}

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Home Edition" /noexecute=optin /fa
stdetect

Write and read text file using StreamWriter

using System;
using System.IO;
public class MainClass
{
    public static int Main(string[] args)
    {
    FileInfo f = new FileInfo("test.txt");
    StreamWriter writer = f.CreateText();
    writer.WriteLine("string 1");
    writer.WriteLine("string 2");
    
    for(int i = 0; i < 10; i++)
    {
      writer.Write(i + " ");
    }
    writer.Write(writer.NewLine);
    writer.Close();
    // Now read it all back in.
    StreamReader sr = File.OpenText("test.txt");
    string input = null;
    while ((input = sr.ReadLine()) != null)
    {
      Console.WriteLine (input);
    }
        return 0;
    }
}

string 1
string 2
0 1 2 3 4 5 6 7 8 9

Write text file line by line

using System;
using System.IO;
class MainClass
{
  public static void Main() 
  {
    FileStream outStream = File.Create("c:\\Test.txt");
    StreamWriter sw = new StreamWriter(outStream);
    sw.WriteLine("This is a test of the StreamWriter class");
    sw.Flush();
    sw.Close();
    StreamReader sr = new StreamReader("c:\\Test.txt");
    string FirstLine;
  
    FirstLine = sr.ReadLine();
    Console.WriteLine(FirstLine);
    sr.Close();
  }
}

Write to a file

using System; 
using System.IO;  
 
class MainClass { 
  public static void Main(string[] args) { 
    FileStream fout; 
 
    // open output file 
    try { 
      fout = new FileStream("test.txt", FileMode.Create); 
    } catch(IOException exc) { 
      Console.WriteLine(exc.Message + "\nError Opening Output File"); 
      return; 
    } 
 
    // Write the alphabet to the file. 
    try { 
      for(char c = "A"; c <= "Z"; c++) 
        fout.WriteByte((byte) c); 
    } catch(IOException exc) { 
      Console.WriteLine(exc.Message + "File Error"); 
    } 
 
    fout.Close(); 
  } 
}