Categories on atreezilla

Cycles C#

Sun, 12 Mar 2023 00:00:00 +0000

The use of loops in C# is briefly described in the article.

for (int i = 0; i < 9; i++)
{
 if (i == 5)
 break;
 //continue;
 Console.Write(i);
}

int i = 60;
while (i > 0)
{
 Console.WriteLine(
 Convert.ToString(i, 2).PadLeft(8, '0'));
 i--;
}

i = -1;
do
{
 Console.Write(i);
 i--;
} while (i > 0);

int[] numbers =
new int[] { 1, 2, 3, 4, 5 };
foreach (int i in numbers)
{
 Console.Write(i);
}

Data types C#

Sun, 12 Mar 2023 00:00:00 +0000

Data types in C# are described in a compressed format .

`Data types in C# are described in compressed format .

//(1 byte) System.Boolean
bool isStupid = false; bool isSmarty = true;
//(1 byte) from 0 to 255 System.Byte
byte_month = 1; byte DayOfWeek = 102;
//(1 byte) integer from -128 to 127
//System.SByte
sbyte t1 = -101; sbyte t2 = 102;
//(2 bytes) integer from -32768 to 32767
//System.Int16
short n1 = 1; short n2 = 102;
//(2 bytes) integer from 0 to 65535
//System.UInt16
ushort un1 = 1; ushort un2 = 102;
//(4 bytes) integer
//from -2147483648 to 2147483647 System.Int32
int age = 10; int b = 0b101; int c = 0xFF;
//(4 bytes) integer from 0 to 4294967295
//System.UInt32
uint ua = 10; uintub = 0b101;
uint uc = 0xFF; uint xa = 10U;
//(8 bytes) integer
// from -9 223 372 036 854 775 808
// up to 9 223 372 036 854 775 807
//System.Int64
long la = -10; long lb = 0b101;
longlc = 0xFF; long xb = 20L;
//(8 bytes) integer
// from 0 to 18 446 744 073 709 551 615
//System.UInt64
ulong ga = 10; ulong gb = 0b101;
ulong gc = 0xFF; ulongxc = 30UL;
//(4 bytes) floating point number
//from -3.4*1038 to 3.4*1038 System.Single
float fa = 3.14F; float fb = 30.6f;
//(8 bytes) floating point number
// from ±5.0*10-324 to ±1.7*10308 System.Double
double db=10.222;
//(16 bytes) decimal fractional number.
// If used without a decimal point,
// has the meaning
// from ±1.0*10-28 to ±7.9228*1028,
// can store 28 decimal places
// System.Decimal
decimal fc = 1005.8M; decimal d = 334.8m;
//(2 bytes) stores a single character
//encoded in Unicode System.Char
char ca = 'A'; char cb = '\x5A';
char cc = '\u0420';
//stores the Unicode character set
//System.String
stringname = "Tom";
/*can store a value of any type
data and occupies 4 bytes
on a 32-bit platform and 8 bytes
on a 64-bit platform.
System.Object , is the base for
all other .NET types and classes*/
object oa = 22; object ob = 3.14;
object oc = "hello code";

Console.WriteLine(
$"Name: {name} \n Age: {age}");
//Implicit typing
var xhello = "Hell to World";
var xc2 = 20;
Console.WriteLine(c.GetType().ToString());
Console.WriteLine(
xhello.GetType().ToString());

Console.WriteLine(
Convert.ToString(123, 2).PadLeft(16, '0')) ;
Console.WriteLine(
"Size of bool {0}",sizeof(bool));

data_types.workbook

Files C#

Sun, 12 Mar 2023 00:00:00 +0000

Examples of working with binary and text files C#

Creation methods:

FileStream(string filename, FileMode mode) ,
FileMode(Append,Create,CreateNew,Open,OpenOrCreate,Truncate)
File.Open(string file, FileMode mode),
File.OpenRead(string file), File.OpenWrite(string file);

Main properties: Length, Position

Main methods:

CopyTo(Stream destination),
int Read(byte[] array, int offset, int count),
long Seek(long offset, SeekOrigin origin),
void Write(byte[] array, int offset, int count)
ValueTask WriteAsync(byte[] array, int offset, int count),
Task CopyToAsync(Stream destination)

Helper classes: StreamReader and StreamWriter text BinaryWriter, BinaryReader binary data

SeekOrigin.Begin: the beginning of the file, SeekOrigin.End: the end of the file, SeekOrigin.Current: the current position in the file
fstream.Seek(-5, SeekOrigin.End);

Ways to use:

try
{
 fstream=
new FileStream(@"f.dat",
FileMode.OpenOrCreate);
}
catch(Exceptionex)
{
}
finally
{
 if (fstream != null)
 fstream.Close();
}

or using

using (var fs =
 new FileStream(@"filePath",
 FileMode…, FileAccess…))

{

}

Working with text files

using System;
using System.Text;
using System.Threading.Tasks;
using System.IO;

FileStream fs =
new FileStream(@"ft.txt",
FileMode.OpenOrCreate, FileAccess.Write);
using (var sw = new StreamWriter(fs)){
 sw.WriteLine(@"text\file");
}
fs.Close();

using(varfsr=
 new FileStream(@"ft.txt", FileMode.Open,
 FileAccess.Read))
{
using (var sr= new StreamReader(fsr))
{
varstr = sr.ReadLine();
Console Write(str);
}
}

Working with binary files

using (var fs = new FileStream(@"fb.bin", FileMode.OpenOrCreate, FileAccess.Write)){
 using (var bw = new BinaryWriter(fs))
 {
 bw Write((int)200);
 }
}
using (var fs = File.OpenRead(@"fb.bin")){
 using (var br = new BinaryReader(fs)){
 varv = br.ReadInt32();
 Console.WriteLine(v);
 }
}

files.workbook

Strings C#

Sun, 12 Mar 2023 00:00:00 +0000

C# String Examples

String initialization

string s1 = "hello";
string s2 = null;

string s3 = new String('a', 6);
// result will be the string "aaaaaa"
string s4 =
new String(
new char[]{'w', 'o', 'r', 'l', 'd'});
var s5 = String.Empty;
if (s5.IsNullOrWhiteSpace()){
Console.WriteLine([Empty String]);
}

Main methods of the String class:

Compare,CompareOrdinal: compares two strings
Contains: whether the substring is contained in the string
Concat: concatenate strings
CopyTo: copies to another line
EndsWith: whether end of string matches substring
Format: formats a string
IndexOf: index of first occurrence
Insert: inserts a substring into a string
Join: joins array elements
LastIndexOf: index of last occurrence
Replace: replaces
Split: splits into an array
Substring: extracts a substring from a string
ToLower: to lowercase
ToUpper: upper case
Trim: remove spaces

long number1 = 19876543210;
Console.WriteLine(
number1.ToString("+# (###) ###-##-##"));
// +1 (987) 654-32-10
Console.WriteLine(
$"{number1:+# ### ### ## ##}");
// +1 987 654 32 10
double number = 23.7;
stringresult =
 String.Format("{0:C}", number);

All used formats:

C / c currency format
D / d Integer format
E / e Exponential notation
F / f Fixed-point decimal format
G / g Specifies the shorter of the two formats: F or E
N/n fixed-point decimal format
p / p Specifies whether a percent sign is displayed next to a number
X / x Hexadecimal number format

' Single quote -" double quote
\ backslash
\0 Null
\a Warning -\b backspace
\f Form feed
\n Newline
\r carriage return
\t Horizontal tab
\v Vertical tab
\u (UTF-16) (0000 - FFFF; \u00E7 = “ç”)
\U (UTF-32) ( 000000 - 10FFFF; \U0001F47D = “👽”)
\x \xH[H][H][H] ( 0 - FFFF; \x00E7 or \x0E7 or \xE7 = “ç”)

Structures C#

Sun, 12 Mar 2023 00:00:00 +0000

Structure description, tuples, enums

Enums

enum Time : byte
{
 Morning,
 Afternoon,
 Evening,
 Night
}

Tuples

(int,int) t1 = (5, 10);
(int x, int y) t2 = (x:1, y:2);
var t3 = (x:3, y:4);
private static (int, int) GetValues()
{
 var result = (1, 3);
 return result;
}

Structures

struct User
{
 public string name;
 public int age;
 public void DisplayInfo()
 {
 Console.WriteLine(
 $"Name: {name} Age: {age}");
 }
}
User tom;
tom.name = "Tom";
tom.age = 34;
tom.DisplayInfo();

Classes

class User
{
 private string _name;
 private int _age;
 public string Name {
 get {return _name;}
 set {_name =value;}}
 public int Age {
 get {return _age;} }
 public User(string name
 ,int age)
 {
 _name =name;
 _age = age;
 }
 public void DisplayInfo(
 params int[] ar)
 {
 foreach(var item in ar)
 {
 Console.WriteLine(item);
 }
 Console.WriteLine(
 $"Name: {Name} Age: {Age}");
 }
}
User tom = new User("Serg",44);
tom.DisplayInfo(1,2,3,4);

Arrays in C#. Initialization

Sat, 11 Mar 2023 00:00:00 +0000

Described types of C# arrays (one-dimensional arrays, multidimensional arrays, array of arrays), methods of initializing arrays .

Single-Dimensional Arrays

var r1 = new int[3] { 1, 2, 3 };
var r2 = new int[] { 1, 2, 3 };
var r3 = new[] { 1, 2, 5 };
int[] r4 = { 1, 3, 5 };
r4[0] = 7;
for ( int i=0; i < r4.Length; i++ )
{
 Console.Write( r4[i] );
}

Multidimensional Arrays

int[,] r2 = new int[2, 3];

var r3 = new int[2, 3]
 { { 0, 1, 2 }, { 3, 4, 5 } };

var r4 = new int[,]
 { { 0, 1, 2 }, { 3, 4, 5 } };

var r5 = new [,]
 { { 0, 1, 2 }, { 3, 4, 5 } };

int[,] r6 =
 { { 0, 1, 2 }, { 3, 4, 5 } };

r6[1,2] = 7;
Console.WriteLine("r6.Rank = {0} ", r3.Rank);

foreach (var i in r6){
 Console.Write("{0} ", i);
}

Jagged Arrays

int[][] r = new int[2][];
r[0] = new int[2] { 1, 2 };
r[1] = new int[3] { 1, 2, 3 };

var r2 = new int[3][];
r2[0] = new int[2] { 1, 2 };
r2[1] = new int[1] { 1 };
r2[2] = new int[5] { 4,1, 2, 3, 5 };

char[][,] r3 =
{
 new char[,]
 { {'H','e'} },
 new char[,]
 { {'l','l'}, {'o',' '} },
 new char[,]
 { {'w','o'}, {'r','l'},
 {'d', '!'} }
};

foreach (var a1 in r3)
{
 foreach (var a2 in a1)
 {
 Console.Write(a2);
 }
}

int[] r0 =
 { 3, 4, 5 };

int[,] r1 =
 { { 0, 1, 2 }, { 3, 4, 5 } };

int[,,] r2 =
 {
 { {0, 1, 2}, {0, 1, 2} }
 ,{ {3, 4, 5}, {0, 1, 2} }
 ,{ {3, 4, 5}, {0, 1, 2} }
 ,{ {3, 4, 5}, {0, 1, 2} }
 ,{ {3, 4, 5}, {0, 1, 2} }
 };
for (int i = 0; i < r2.Rank; i++)
{
 Console.Write( r2.GetLength(i)+",");
}
var l = 1;
Console.WriteLine( l);
for (int i = 0; i < r2.Rank; i++)
{
 l*=r2.GetLength(i);

}
Console.WriteLine("");
Console.WriteLine(
"Length {0}=={1}",l,r2.Length);

Console.WriteLine(
"r0.Rank = {0} ", r0.Rank);
Console.WriteLine(
"r1.Rank = {0} ", r1.Rank);
Console.WriteLine(
"r2.Rank = {0} ", r2.Rank);

foreach (int i in r2)
{
Console.Write(i);
}

Collections C#. Definition, examples of use. Analogies.

Sat, 11 Mar 2023 00:00:00 +0000

Describing C# Collections. Definition, examples of use. Analogies

Collections

A collection is an object that contains a set of values and allows you to interact with these values (view, add, modify, delete, sort …) .

Classification of collections by characteristics

Permanent, dynamic
Can store objects of the same type or objects of different types

Classifying collections according to the logic of organization

Vector - Array
Matrix - Two-dimensional array
Multidimensional array
List - Ordered collection of objects
Stack - last in - first out LIFO
Queue - first in - first out FIFO
Associative array (dictionary) - an unordered collection that stores key-value pairs
Set - an unordered collection that stores a set of unique values
A multiset is a set that allows the presence of several identical values at the same time.

Classify collections by implementation

Collection interfaces

IEnumerable<T>: defines the GetEnumerator method, you can get the elements of any collection The implementation of the interface allows you to iterate over the elements of the collection using foreach

ICollection<T>: represents common properties and methods for all generic collections (e.g. CopyTo, Add, Remove, Contains methods, Count property)

IList<T>: provides functionality for creating sequential lists

IComparer<T>: defines the Compare method for comparing two objects of the same type

IDictionary<TKey, TValue>: collection must store objects as key-value pairs TKey, TValue

IEqualityComparer<T>: defines methods by which two objects of the same type are compared for equality

are implemented by collection classes in the System.Collections.Generic namespace:

Required namespaces

using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;

Collection types C#

Array

ArrayList objectList =
new ArrayList()
{ 1, 2, "string", 'c', 2.0f };

Singly linked list List<T>: sequential list. Implements interfaces IList<T>, ICollection<T>, IEnumerable<T>

List<int> numbers =
new List<int>() { 1, 2, 3, 45 };

SortedSet<T>: a sorted collection of objects of the same type. Implements interfaces ICollection<T>, ISet<T>, IEnumerable<T>

SortedList<TKey, TValue>:stores sets of key-value pairs sorted by key. Implements interfaces ICollection<T>, IEnumerable<T>, IDictionary<TKey, TValue>

Doubly linked list LinkedList<T>: Doubly linked list. Implements interfaces ICollection<T> , IEnumerable<T>

LinkedList<int> numbers1 =
new LinkedList<int>();

Stack Stack<T>: stack of similar objects. Implements interfaces ICollection<T> , IEnumerable<T>

Stack<int> numbers3 =
new Stack<int>();

Hash table Hashtable interfaces are implemented IDictionary, ICollection, IEnumerable, ISerializable, IDeserializationCallback и ICloneable

Hashtable htbl = new Hashtable();
htbl.Add("name", "key123");

Bit array BitArray(byte[] bytes) And(),Get(),Not(),Or(),Set(),SetAll(),Xor()

BitVector32 CreateMask() CreateSelection()

BitArray bits1 = new BitArray(10);
var bits2 = new BitVector32 () ;

Queue Queue<T>: FIFO(“first in, first out”). Implements interfaces ICollection, IEnumerable<T>

Queue<int> numbers2 =
new Queue<int>();

Dictionary Dictionary<TKey, TValue>: “key-value”. Implements interfaces ICollection<T>, IEnumerable<T>, IDictionary<TKey, TValue>

Dictionary<int, string> countries =
new Dictionary<int, string>(5);

SortedDictionary<TKey, TValue>: stores sets of key-value pairs sorted by key. Similar to the SortedList<TKey, TValue> class, the main differences are only in memory usage and speed of insertion and deletion

Ways to create collections

IEnumerable<int> randomCol =
Enumerable.Range(1, 10);

foreach (var item in randomCol)
 {
 Console.WriteLine((item.ToString());
 }

var r = new Random(Seed:5);
var rVal = r.Next(minValue:1,maxValue:10);

IEnumerable<int> squares =
Enumerable.Range(20, 30).Select(x => x * rVal);

Iterators and the yield statement

using System.Collections;
Numbers numbers = new Numbers();
foreach (int n in numbers)
{
Console.WriteLine(n);
}
class Numbers
{
 public IEnumerator GetEnumerator()
 {
 for(int i = 0; i < 6; i++)
 {
 yield return i * i;
 }
 }
}

collections.workbook

Arithmetic operations in C#

Fri, 26 Mar 2021 00:00:00 +0000

The article briefly describes C# arithmetic operations as well as ways to convert types

+ , - , * , / , % , ++ , --

Bitwise Operations

&(logical multiplication),
|(logical addition),
^(logical XOR),
~ (logical negation or inversion)

Assignment operations

+= , -= , *= , /= , %= , &= , |= , ^= , <<= , >>=

Conditional expressions

==,!=,<,>,<=,>=,|,^,&,||,&&,!

What types can be safely converted to

byte » short, ushort, int, uint, long, ulong, float, double, decimal
sbyte » short, int, long, float, double, decimal
short » int, long, float, double, decimal
ushort » int, uint, long, ulong, float, double, decimal
int » long, float, double, decimal
uint » long, ulong, float, double, decimal
long » float, double, decimal
ulong » float, double, decimal
float » double
char » ushort, int, uint, long, ulong, float, double, decimal

Conversion

int x=500;
long y=(int)x;
Console.WriteLine(y);

uint u =10;
float f =101;
uint.TryParse(f.ToString(),out u);
Console.WriteLine(u);
y++;
Console.WriteLine(
"16 - numeric representation of a number {0} - {1}"
,y , Convert.ToString(y,16));
Console.WriteLine(
Convert.ToUInt16(++f));

Conditional constructs C#

Fri, 26 Mar 2021 00:00:00 +0000

Discussed use cases for C# conditional constructs

var x=11;
if(x > 2){
Console.WriteLine(
$"Число {x} больше числа 2");}
else if (x < 2){
Console.WriteLine(
$"Число {x} меньше числа 2");}

string selection="";
switch (selection)
{
 case "Y":
 Console.WriteLine(
 "Вы нажали букву Y");
 break;
 case "N":
 Console.WriteLine(
 "Вы нажали букву N");
 break;
 default:
 Console.WriteLine(
 "Вы нажали неизвестную букву");
 break;
}
int z = selection=="Y"? (1+2) : (3-1);