Csharp/CSharp Tutorial/File Directory Stream/FileStream

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Binary File Reading through FileStream

<source lang="csharp">using System; using System.Collections.Generic; using System.ruponentModel; using System.Data; using System.Drawing; using System.Text; using System.Windows.Forms; using System.IO; public class MainClass { 

   public static void Main() {
       int nCols = 16;
       FileStream inStream = new FileStream("c:\\a.txt", FileMode.Open, FileAccess.Read);
       long nBytesToRead = inStream.Length;
       if (nBytesToRead > 65536 / 4)
           nBytesToRead = 65536 / 4;
       int nLines = (int)(nBytesToRead / nCols) + 1;
       string[] lines = new string[nLines];
       int nBytesRead = 0;
       for (int i = 0; i < nLines; i++) {
           StringBuilder nextLine = new StringBuilder();
           nextLine.Capacity = 4 * nCols;
           for (int j = 0; j < nCols; j++) {
               int nextByte = inStream.ReadByte();
               nBytesRead++;
               if (nextByte < 0 || nBytesRead > 65536)
                   break;
               char nextChar = (char)nextByte;
               if (nextChar < 16)
                   nextLine.Append(" x0" + string.Format("{0,1:X}", (int)nextChar));
               else if
                   (char.IsLetterOrDigit(nextChar) || char.IsPunctuation(nextChar))
                   nextLine.Append("  " + nextChar + " ");
               else
                   nextLine.Append(" x" + string.Format("{0,2:X}", (int)nextChar));
           }
       }
       inStream.Close();

   }

}</source>

Demonstrate random access file

<source lang="csharp">using System; using System.IO;

class MainClass { 

 public static void Main() { 
   FileStream f; 
   char ch; 

   try { 
     f = new FileStream("random.dat", FileMode.Create); 
   } 
   catch(IOException exc) { 
     Console.WriteLine(exc.Message); 
     return ; 
   } 

   // Write the alphabet.      
   for(int i=0; i < 26; i++) { 
     try { 
       f.WriteByte((byte)("A"+i)); 
     }  
     catch(IOException exc) { 
       Console.WriteLine(exc.Message); 
       return ; 
     } 
   } 

   try { 
     f.Seek(0, SeekOrigin.Begin); // seek to first byte 
     ch = (char) f.ReadByte(); 
     Console.WriteLine("First value is " + ch); 

     f.Seek(1, SeekOrigin.Begin); // seek to second byte 
     ch = (char) f.ReadByte(); 
     Console.WriteLine("Second value is " + ch); 

     f.Seek(4, SeekOrigin.Begin); // seek to 5th byte 
     ch = (char) f.ReadByte(); 
     Console.WriteLine("Fifth value is " + ch); 

     Console.WriteLine(); 

   }  
   catch(IOException exc) { 
     Console.WriteLine(exc.Message); 
   } 
 
   Console.WriteLine(); 
   f.Close(); 
 }

}</source> 

First value is A
Second value is B
Fifth value is E

Is a stream seekable

<source lang="csharp">using System; using System.IO; public class MainClass { 

   public static void Main() {
       byte[] buf2 = new byte[] { 97, 112, 112, 108, 101, 115, 97, 117, 99, 101 };
       FileStream s = new FileStream("Foo.txt", FileMode.Open);
       Console.WriteLine("Length: {0}, Position: {1}", s.Length, s.Position);
       if (s.CanSeek) {
           s.Seek(13, SeekOrigin.Begin);
           Console.WriteLine(
               "Position: {0}", s.Position);
           s.Write(buf2, 0, buf2.Length);
       }
   }

}</source>

Move file pointer to beginning of file

<source lang="csharp">using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; 

   class Program
   {
       static void Main(string[] args)
       {
           FileStream aFile = new FileStream("Temp.txt", FileMode.Create);
           char[] charData = "this is a test.".ToCharArray();
           byte[] byData = new byte[charData.Length];
           Encoder e = Encoding.UTF8.GetEncoder();
           e.GetBytes(charData, 0, charData.Length, byData, 0, true);
           // Move file pointer to beginning of file.
           aFile.Seek(0, SeekOrigin.Begin);
           aFile.Write(byData, 0, byData.Length);
       }
   }</source>

Open a file with exception handling

<source lang="csharp">FileStream fin;

try { 

 fin = new FileStream("test.dat", FileMode.Open);

} catch(FileNotFoundException exc) { 

 Console.WriteLine(exc.Message); 
 return;

} catch { 

 Console.WriteLine("Cannot open file."); 
 return;

}</source>

Open an existing file

<source lang="csharp">using System; using System.IO; public class MainClass { 

 static void Main(string[] args)
 {
   FileInfo MyFile = new FileInfo(@"c:\Testing.txt");
   FileStream MyStream;
   MyStream = MyFile.Open(FileMode.Open, FileAccess.Read, FileShare.None);
 }

}</source>

Read every other value using FileSeek

<source lang="csharp">using System; using System.IO;

class MainClass { 

 public static void Main() { 
   FileStream f; 
   char ch; 

   try { 
     f = new FileStream("random.dat", FileMode.Create); 
   } 
   catch(IOException exc) { 
     Console.WriteLine(exc.Message); 
     return ; 
   } 

   // Write the alphabet.      
   for(int i=0; i < 26; i++) { 
     try { 
       f.WriteByte((byte)("A"+i)); 
     }  
     catch(IOException exc) { 
       Console.WriteLine(exc.Message); 
       return ; 
     } 
   } 

   try { 
     Console.WriteLine("Here is every other value: "); 
     for(int i=0; i < 26; i += 2) { 
       f.Seek(i, SeekOrigin.Begin); // seek to ith double 
       ch = (char) f.ReadByte(); 
       Console.Write(ch + " "); 
     } 

   }  
   catch(IOException exc) { 
     Console.WriteLine(exc.Message); 
   } 
 
   Console.WriteLine(); 
   f.Close(); 
 }

}</source> 

Here is every other value:
A C E G I K M O Q S U W Y

Read file stream as an array of bytes

<source lang="csharp">using System; using System.IO; public class MainClass { 

 static void Main(string[] args)
 {
   FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);
   int NumberOfBytes = 200;
   byte[] MyByteArray = new Byte[NumberOfBytes];
   int BytesRead = MyFileStream1.Read(MyByteArray, 0, NumberOfBytes);
   
   MyFileStream1.Close();    
 }

}</source>

Read file stream on a per byte basis

<source lang="csharp">using System; using System.IO; public class MainClass { 

 static void Main(string[] args)
 {
   FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);
   
   int MyBytes = MyFileStream1.ReadByte();
   
   MyFileStream1.Close();    
 }

}</source>

Reset internal position for a FileStream

<source lang="csharp">using System; using System.IO; public class MainClass { 

   public static int Main(string[] args)
   {      
   FileInfo f = new FileInfo(@"C:\test.txt");
   FileStream  s = f.Open(FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None);    
   for(int i = 0; i < 256; i++)
   {
     s.WriteByte((byte)i);
   }
   // Reset internal position.
   s.Position = 0;
   for(int i = 0; i < 256; i++)
   {
     Console.Write(s.ReadByte());  
   }
   s.Close();
   f.Delete();
       return 0;
   }

}</source>

Text File Reading with FileStream

<source lang="csharp">using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; 

   class Program
   {
       static void Main(string[] args)
       {
           byte[] byData = new byte[200];
           char[] charData = new Char[200];
           FileStream aFile = new FileStream("Program.cs", FileMode.Open);
           aFile.Seek(113, SeekOrigin.Begin);
           aFile.Read(byData, 0, 200);
           Decoder d = Encoding.UTF8.GetDecoder();
           d.GetChars(byData, 0, byData.Length, charData, 0);
           Console.WriteLine(charData);
       }
   }</source>

The FileMode and FileAccess

Value Description FileMode.Append append to the end of file. FileMode.Create create a new output file. Any preexisting file by the same name will be destroyed. FileMode.CreateNew create a new output file. The file must not already exist. FileMode.Open open a preexisting file. FileMode.OpenOrCreate open a file if it exists, or create the file if it does not already exist. FileMode.Truncate open a preexisting file, but reduce its length to zero.

If you want to restrict access to just reading or just writing, use this constructor:


<source lang="csharp">FileStream(string filename, FileMode mode, FileAccess how)</source>

Use FileStream to read a file byte by byte

<source lang="csharp">using System; using System.Windows.Forms; using System.IO; class MainClass { 

 public static void Main() 
 {
   OpenFileDialog dlgOpen = new OpenFileDialog();
   dlgOpen.Title="Select file to back up";
   if (dlgOpen.ShowDialog() == DialogResult.OK)
   {
     FileStream inStream = File.OpenRead(dlgOpen.FileName);
     FileStream outStream =  File.OpenWrite(dlgOpen.FileName + ".bak");
     int b;
     while ((b = inStream.ReadByte()) > -1)
       outStream.WriteByte( (byte) b);
     outStream.Flush();
     outStream.Close();
     inStream.Close();
   }
 }

}</source>

Use FileStream to read a file selected from OpenFileDialog

<source lang="csharp">using System; using System.Windows.Forms; using System.IO; class MainClass { 

 public static void Main() 
 {
   OpenFileDialog dlgOpen = new OpenFileDialog();
   dlgOpen.Title="Select file to back up";
   if (dlgOpen.ShowDialog() == DialogResult.OK)
   {
     FileStream inStream = File.OpenRead(dlgOpen.FileName);
     FileStream outStream =  File.OpenWrite(dlgOpen.FileName + ".bak");
     int b;
     while ((b = inStream.ReadByte()) > -1)
       outStream.WriteByte( (byte) b);
     outStream.Flush();
     outStream.Close();
     inStream.Close();
   }
 }

}</source>

Use FileStream to write/read a file byte by byte

<source lang="csharp">using System; using System.Windows.Forms; using System.IO; class MainClass { 

 public static void Main() 
 {
   OpenFileDialog dlgOpen = new OpenFileDialog();
   dlgOpen.Title="Select file to back up";
   if (dlgOpen.ShowDialog() == DialogResult.OK)
   {
     FileStream inStream = File.OpenRead(dlgOpen.FileName);
     FileStream outStream =  File.OpenWrite(dlgOpen.FileName + ".bak");
     int b;
     while ((b = inStream.ReadByte()) > -1)
       outStream.WriteByte( (byte) b);
     outStream.Flush();
     outStream.Close();
     inStream.Close();
   }
 }

}</source>

using statement and FileStream

<source lang="csharp">using System; using System.Collections.Generic; using System.Text; using System.IO; 

 class Program
 {
   static void Main(string[] args)
   {
     using (FileStream fStream = File.Open(@"C:\myMessage.dat",FileMode.Create))
     {
       string msg = "Hello!";
       byte[] msgAsByteArray = Encoding.Default.GetBytes(msg);
       fStream.Write(msgAsByteArray, 0, msgAsByteArray.Length);
       fStream.Position = 0;
       byte[] bytesFromFile = new byte[msgAsByteArray.Length];
       for (int i = 0; i < msgAsByteArray.Length; i++)
       {
         bytesFromFile[i] = (byte)fStream.ReadByte();
         Console.Write(bytesFromFile[i]);
       }
       Console.WriteLine(Encoding.Default.GetString(bytesFromFile));
     }
   }
 }</source>

Write byte array with FileStream

<source lang="csharp">using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; 

   class Program
   {
       static void Main(string[] args)
       {
           FileStream aFile = new FileStream("Temp.txt", FileMode.Create);
           char[] charData = "this is a test.".ToCharArray();
           byte[] byData = new byte[charData.Length];
           Encoder e = Encoding.UTF8.GetEncoder();
           e.GetBytes(charData, 0, charData.Length, byData, 0, true);
           // Move file pointer to beginning of file.
           aFile.Seek(0, SeekOrigin.Begin);
           aFile.Write(byData, 0, byData.Length);
       }
   }</source>

Write data to file through FileStream per byte

<source lang="csharp">using System; using System.IO; public class MainClass { 

 static void Main(string[] args)
 {
   FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);
   byte MyWriteByte = 100;
   MyFileStream1.WriteByte(MyWriteByte);
   
   MyFileStream1.Close();    
 }

}</source>

Write data to file through FileStream via an array

<source lang="csharp">using System; using System.IO; public class MainClass { 

 static void Main(string[] args)
 {
   FileStream MyFileStream1 = new FileStream(@"c:\Testing.txt", FileMode.Create);
   int NumberOfBytesToWrite = 256;
   byte[] MyWriteByteArray = new Byte[NumberOfBytesToWrite];
   for (int i = 0; i < 256; i++)
   {
     MyWriteByteArray[i] = (byte)i;
     i++;
   }
   MyFileStream1.Write(MyWriteByteArray, 0, NumberOfBytesToWrite);
   
   MyFileStream1.Close();    
 }

}</source>

Write/read bytes using FileStream

<source lang="csharp">using System; using System.IO; public class MainClass { 

   public static int Main(string[] args)
   {
   FileStream myFStream = new FileStream("test.dat", FileMode.OpenOrCreate, FileAccess.ReadWrite);
     
   for(int i = 0; i < 256; i++)
     myFStream.WriteByte((byte)i);
   myFStream.Position = 0;
   for(int i = 0; i < 256; i++)
     Console.Write(myFStream.ReadByte());  
   Console.WriteLine();
   myFStream.Close();
   return 0;
   }

}</source> 

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