Streams and Text Files
Telerik Academy Alpha
Table of contents
What is a stream?
What is a stream?
-
A stream is an abstraction of a sequence of bytes.
-
Can be accessed in sequential order (pipe with water flowing through it)
-
Text files, Images, Network access
-
-
-
Two main streams
-
Input stream (read data)
-
Output stream (write date)
-
-
System.IO namespace in C#
What is a stream?
Program
Input stream
Output stream
Input Source (keyboard, file, network, etc.)
Output Sink (console, file, network, etc.)
What is a stream?
- Stream must be open when needed
- and closed when you don't need it anymore
- It is the programmer responsibility
- can be done with using() block
Stream fileStream = new FileStream("../../../test.jpg", FileMode.Open, FileAccess.Read);
// Do some operations with the file stream
// Close the stream
fileStream.Close();
// The stream is automatically closed
using (fileStream = new FileStream("../../../test.jpg", FileMode.Open, FileAccess.Read))
{
// Do some operations with the file stream
}File streams, readers, writers
File streams
- With FileStream you can read/write bytes from file
// Write new string to file
string str = "Telerik Academy Alpha";
using(FileStream fileStream = new FileStream("../../../test.txt", FileMode.Open))
{
for (int i = 0; i < str.Length; i++)
{
fileStream.WriteByte((byte)str[i]);
}
}
// Read all chars
using (FileStream fileStream = new FileStream("../../../test.txt", FileMode.Open))
{
for (int i = 0; i < fileStream.Length; i++)
{
Console.Write((char)fileStream.ReadByte());
}
}
File streams and writers/readers
-
StreamReader/Writer vs FileStream
-
streams handle bytes
-
readers/writers handle characters
-
var reader = new StreamReader("../../../test.txt");
Console.WriteLine((char)reader.Read()); // output: T
// Should close it before using it again below
// Otherwidse the file will be in use
reader.Close();
FileStream fileStream = new FileStream("../../../test.txt", FileMode.Open);
Console.WriteLine((char)fileStream.ReadByte()); // output: T
fileStream.Close();Readers/writers
-
StreamReader/Writer
-
Reader (byte[] to string)
-
Writer (string to byte[])
-
using (var reader = new StreamReader("../../../test.txt"))
{
Console.WriteLine(reader.ReadLine()); // Telerik Academy
// More methods: reader.ReadToEnd();
}
using (var writer = new StreamWriter("../../../test.txt"))
{
writer.WriteLine("Telerik Academy Alpha"); // Writes to text file
// More methods: writer.Write();
}Combine them
-
Combine Stream and StreamReader/Writer
-
StreamReader/Writer accepts stream or path
-
using (FileStream fileStream = new FileStream("../../../test.txt", FileMode.Open))
{
var reader = new StreamReader(fileStream);
Console.WriteLine(reader.ReadLine()); // Telerik Academy
}Files
Text Files
TextFiles
-
You could read or write text files with wrappers over a stream
-
Both StreamReader/Writer and File classes are wrappers over streams
-
Both could read all lines of text from a file
-
StreamReader/Writer gives more control
-
It could read/write file without loading the whole file
-
-
File makes your code shorter and more understandable
-
TextFiles
using (StreamReader reader = new StreamReader("../../../test.txt"))
{
Console.WriteLine(reader.ReadToEnd());
}
Console.WriteLine(File.ReadAllText("../../../test.txt"));-
Below code is reading all the text from a file with the two options
-
StreamReader
-
File
-
TextFiles
-
StreamReader/Writer could read/write to/from files line by line
-
This is very useful for certain situations
-
-
You should choose which class to use (File or StreamReader/Writer) depending on your code requirements
-
There is no right or wrong
Other Files
Copy file
// Copy an image
// This reads the file as a byte array
// You could use any other method or class
byte[] arr = File.ReadAllBytes("../../../test.jpg");
// This writes the file to the file system
File.WriteAllBytes("../../../test-copy.jpg", arr);-
You can copy any file
-
Image
-
Text file
-
pdf
-
etc.
-
Modify file
// This will read the file as byte[]
// then it will save another file with bytes only at the even positions
// if the file is an image/pdf or another type of file it will be corrupted
// but if it is a text file it will have missing parts
byte[] arr = File.ReadAllBytes("../../../test.pdf");
List<byte> list = new List<byte>();
for (int i = 0; i < arr.Length; i++)
{
if (i % 2 == 0)
{
list.Add(arr[i]);
}
}
File.WriteAllBytes("../../../test-part.pdf", list.ToArray());Questions?
[C#] Streams and files
By telerikacademy
