Chapter 9: Working with Files, Streams, and Serialization

Question 1

System.IO.Directory;
can you say some useful methods of this library?

Answer 1

handle cross-platform environments
Directory.GetDirectories()
Directory.Exists()
Directory.CreateDirectory()
Directory.Delete()

Question 2

System.IO.Path
can you say some useful methods of this library?

Answer 2

Path.PathSeparator
Path.GetFullPath()
Path.Combine()
Path.GetDirectoryName()
Path.GetExtension()
Path.GetFileName()
Path.GetFileNameWithoutExtension()

Question 3

System.Environment
can you say some useful methods of this library?

Answer 3

Environment.CurrentDirectory
Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments);

Question 4

Managing drives

Answer 4

oreach (DriveInfo drive in DriveInfo.GetDrives())
{
if (drive.IsReady)
{
WriteLine(
“{0,-30} | {1,-10} | {2,-7} | {3,18:N0} | {4,18:N0}”,
drive.Name, drive.DriveType, drive.DriveFormat,
drive.TotalSize, drive.AvailableFreeSpace);
}
else
{
WriteLine(“{0,-30} | {1,-10}”, drive.Name, drive.DriveType);
}
}

Question 5

Managing files

Answer 5

// define a directory path to output files
// starting in the user’s folder
string dir = Combine(
GetFolderPath(SpecialFolder.Personal), “OutputFiles”);
CreateDirectory(dir);
// define file paths
string textFile = Combine(dir, “Dummy.txt”);
string backupFile = Combine(dir, “Dummy.bak”);
WriteLine($”Working with: {textFile}”);
// check if a file exists
WriteLine($”Does it exist? {File.Exists(textFile)}”);
// create a new text file and write a line to it
StreamWriter textWriter = File.CreateText(textFile);
textWriter.WriteLine(“Hello, C#!”);
textWriter.Close(); // close file and release resources
WriteLine($”Does it exist? {File.Exists(textFile)}”);
// copy the file, and overwrite if it already exists
File.Copy(sourceFileName: textFile,
destFileName: backupFile, overwrite: true);
WriteLine(
$”Does {backupFile} exist? {File.Exists(backupFile)}”);
Write(“Confirm the files exist, and then press ENTER: “);
ReadLine();
// delete file
File.Delete(textFile);
WriteLine($”Does it exist? {File.Exists(textFile)}”);
// read from the text file backup
WriteLine($”Reading contents of {backupFile}:”);
StreamReader textReader = File.OpenText(backupFile);
WriteLine(textReader.ReadToEnd());
textReader.Close()

Question 6

Managing paths

Answer 6

WriteLine($”Folder Name: {GetDirectoryName(textFile)}”);
WriteLine($”File Name: {GetFileName(textFile)}”);
WriteLine(“File Name without Extension: {0}”,
GetFileNameWithoutExtension(textFile));
WriteLine($”File Extension: {GetExtension(textFile)}”);
WriteLine($”Random File Name: {GetRandomFileName()}”);
WriteLine($”Temporary File Name: {GetTempFileName()}”);

Question 7

Getting file information

Answer 7

FileInfo info = new(backupFile);
WriteLine($”{backupFile}:”);
WriteLine($”Contains {info.Length} bytes”);
WriteLine($”Last accessed {info.LastAccessTime}”);
WriteLine($”Has readonly set to {info.IsReadOnly}”);

Question 8

How to open a file and read from it?

Answer 8

FileStream file = File.Open(pathToFile,
FileMode.Open, FileAccess.Read, FileShare.Read);

Question 9

How to check a file or directory’s attributes?

Answer 9

FileInfo info = new(backupFile);
WriteLine(“Is the backup file compressed? {0}”,
info.Attributes.HasFlag(FileAttributes.Compressed));

Question 10

Can you tell all of the concreate stream?

Answer 10

FileStream, MemoryStream,
BufferedStream, GZipStream, and SslStream,

Question 11

What are the common members of the Stream class ?

Answer 11

CanRead,
CanWrite
These properties determine if you can read from and write to the stream.
Length, Position
These properties determine the total number of bytes and the current position
within the stream. These properties may throw an exception for some types of
streams.
Dispose This method closes the stream and releases its resources.
Flush If the stream has a buffer, then this method writes the bytes in the buffer to the
stream and the buffer is cleared.
CanSeek This property determines if the Seek method can be used.
Seek This method moves the current position to the one specified in its parameter.
Read, ReadAsync
These methods read a specified number of bytes from the stream into a byte
array and advance the position.
ReadByte This method reads the next byte from the stream and advances the position.
Write,
WriteAsync
These methods write the contents of a byte array into the stream.
WriteByte This method writes a byte to the stream.

Question 12

How to read & write plain text?

Answer 12

File.ReadAllText(textFile);
StreamWriter text = File.CreateText(textFile);
foreach (string item in Viper.Callsigns)
{
text.WriteLine(item);
}
text.Close();

Question 13

How to read & write xml files?

Answer 13

string xmlFile = Combine(CurrentDirectory, “streams.xml”);
FileStream? xmlFileStream = null;
XmlWriter? xml = null;
try
{
xmlFileStream = File.Create(xmlFile);
xml = XmlWriter.Create(xmlFileStream,
new XmlWriterSettings { Indent = true });
xml.WriteStartDocument();
xml.WriteStartElement(“callsigns”);
foreach (string item in Viper.Callsigns)
{
xml.WriteElementString(“callsign”, item);
}
xml.WriteEndElement();
xml.Close();
xmlFileStream.Close();
}
catch (Exception ex)
{
WriteLine($”{ex.GetType()} says {ex.Message}”);
}
finally
{
if (xml != null)
{
xml.Dispose();
WriteLine(“The XML writer’s unmanaged resources have been
disposed.”);
}
if (xmlFileStream != null)
{
xmlFileStream.Dispose();
WriteLine(“The file stream’s unmanaged resources have been
disposed.”);
}
}
WriteLine(“{0} contains {1:N0} bytes.”,
arg0: xmlFile,
arg1: new FileInfo(xmlFile).Length);
WriteLine(File.ReadAllText(xmlFile));

Question 14

Simplifying disposal by using the using statement

Answer 14

using (FileStream file2 = File.OpenWrite(
Path.Combine(path, “file2.txt”)))
{
using (StreamWriter writer2 = new StreamWriter(file2))
{
try
{
writer2.WriteLine(“Welcome, .NET!”);
}
catch (Exception ex)
{
WriteLine($”{ex.GetType()} says {ex.Message}”);
}
} // automatically calls Dispose if the object is not null
}

Question 15

How to compress file by gzip algorithm?

Answer 15

static void Compress(string algorithm = “gzip”)
{
// define a file path using algorithm as file extension
string filePath = Combine(
CurrentDirectory, $”streams.{algorithm}”);
FileStream file = File.Create(filePath);
Stream compressor;
if (algorithm == “gzip”)
{
compressor = new GZipStream(file, CompressionMode.Compress);
}
else
{
compressor = new BrotliStream(file, CompressionMode.Compress);
}
using (compressor)
{
using (XmlWriter xml = XmlWriter.Create(compressor))
{
xml.WriteStartDocument();
xml.WriteStartElement(“callsigns”);
foreach (string item in Viper.Callsigns)
{
xml.WriteElementString(“callsign”, item);
}
}
}
Stream decompressor;
if (algorithm == “gzip”)
{
decompressor = new GZipStream(
file, CompressionMode.Decompress);
}
else
{
decompressor = new BrotliStream(
file, CompressionMode.Decompress);
}
using (decompressor)
using (XmlReader reader = XmlReader.Create(decompressor))
while (reader.Read())
{
// check if we are on an element node named callsign
if ((reader.NodeType == XmlNodeType.Element)
&& (reader.Name == “callsign”))
{
reader.Read(); // move to the text inside element
WriteLine($”{reader.Value}”); // read its value
}
}
}
}

Question 16

How to archive contents into a tar archive?

Answer 16

using System.Formats.Tar; // TarFile

TarFile.CreateFromDirectory(
sourceDirectoryName: sourceDirectory,
destinationFileName: tarFile,
includeBaseDirectory: true);

TarFile.ExtractToDirectory(
sourceFileName: tarFile,
destinationDirectoryName: destinationDirectory,
overwriteFiles: true);

Question 17

How to encoding string as byte array

Answer 17

Encoding.UTF8.GetBytes(message);
and reverse is
Encoding.UTF8.GetString(encoded);

Question 18

How to encoding and decoding text in files?

Answer 18

StreamReader reader = new(stream, Encoding.UTF8);
StreamWriter writer = new(stream, Encoding.UTF8);

Question 19

how to reading and writing with random access handles

Answer 19

using Microsoft.Win32.SafeHandles; // SafeFileHandle
using System.Text; // Encoding
using SafeFileHandle handle =
File.OpenHandle(path: “coffee.txt”,
mode: FileMode.OpenOrCreate,
access: FileAccess.ReadWrite);

string message = “Café £4.39”;
ReadOnlyMemory<byte> buffer = new(Encoding.UTF8.GetBytes(message));
await RandomAccess.WriteAsync(handle, buffer, fileOffset: 0);
long length = RandomAccess.GetLength(handle);
Memory<byte> contentBytes = new(new byte[length]);
await RandomAccess.ReadAsync(handle, contentBytes, fileOffset: 0);
string content = Encoding.UTF8.GetString(contentBytes.ToArray());
WriteLine($"Content of file: {content}");</byte></byte>

Question 20

How to serializing as XML

Answer 20

using System.Xml.Serialization;
XmlSerializer xs = new(type: people.GetType());
string path = Combine(CurrentDirectory, “people.xml”);
using (FileStream stream = File.Create(path))
{
xs.Serialize(stream, people);
}

Question 21

How to generating compact XML?

Answer 21

[XmlAttribute(“fname”)]
public string? FirstName { get; set; }
[XmlAttribute(“lname”)]
public string? LastName { get; set; }
[XmlAttribute(“dob”)]
public DateTime DateOfBirth { get; set; }

Question 22

How to deserializing XML files?

Answer 22

using (FileStream xmlLoad = File.Open(path, FileMode.Open))
{
// deserialize and cast the object graph into a List of Person
List<Person>? loadedPeople =
xs.Deserialize(xmlLoad) as List<Person>;
if (loadedPeople is not null)
{
foreach (Person p in loadedPeople)
{
WriteLine("{0} has {1} children.",
p.LastName, p.Children?.Count ?? 0);
}
}
}</Person></Person>

Question 23

How to serializing & deserializing with json (Newtonsoft.Json)?

Answer 23

Newtonsoft.Json.JsonSerializer.Serialize(jsonStream, people);
Newtonsoft.Json.JsonSerializer.Deserialize(jsonStream, people);c

Question 24

How to use
System.Text.Json.JsonSerializer

Answer 24

List<Person>? loadedPeople =
await System.Text.Json.JsonSerializer.DeserializeAsync(utf8Json: jsonLoad,
returnType: typeof(List<Person>)) as List<Person>;</Person></Person></Person>

Question 25

How to controlling JSON processing?

Answer 25

• Including and excluding fields.
  [JsonInclude] // include this field
  public DateTime PublishDate;
• Setting a casing policy.
• Selecting a case-sensitivity policy.
• Choosing between compact and prettified whitespace
  JsonSerializerOptions options = new()
  {
  IncludeFields = true, // includes all fields
  PropertyNameCaseInsensitive = true,
  WriteIndented = true,
  PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
  };