C#
Data Types:
Data types in C# are referred to as "value types" and "reference types".
When a value type is declared, the data is stored in the memory location of the variable. When a reference type is declared, the data is stored somewhere else in memory and the variable contains a pointer it.
Reference types are always allocated in heap memory,
value types can be allocated on the heap or on the stack depending on where they're declared.
If a value type is declared inside a method, then it's stored on the stack. If it's declared in a class, then the data is stored on the heap. This is because a class is a reference type, which must always be stored on the heap.
Value types include int, byte, bool, and char. Reference types include string, arrays and class.
Integers:
An integer to be negative, it should be declared as a "signed" integer. Otherwise, it can be "unsigned". Unsigned integers can be larger than signed integers because we're not wasting a "sign" bit. We can allocate different sizes for an integer in multiples of 8 bits: 8, 16, 32 and 64 bits.
sbyte
Signed 8-bit
byte
Unsigned 8-bit
short
Signed 16-bit
ushort
Unsigned 16-bit
int
Signed 32-bit
uint
Unsigned 32-bit
long
Signed 64-bit
ulong
Unsigned 64-bit
A floating point is a number that can have decimal places, 8.2, 3.14, etc. declaring a float or double, the letter F or D should be appended to the value. There are three types (all of which are signed):
float
4 bytes
double
8 bytes
decimal
16 bytes
A bool is a true or false value
A char is a single letter or number, represented by an integer
The array and tuple are both types of collections
An array can hold multiple values of a single data type; whereas a tuple can hold multiple values but of various data types
A tuple is declared using parenthesise for both the data types and initial values; and instead of accessing a tuple index via square brackets, we use the period, .. Each item is given a name like Item1, Item2, etc. Can use a concept called "deconstruction" to assign friendly variable names to your elements.
(string, string, int) tuple = ("duck", "goose", 2);
(string firstbird, string secondbird, int numerofbirds);One way is via interpolation, denoted by a prepended $. Another is by using the + operator. Or by using the string.Concat()
string has lots of really useful methods including Split, Join, Equals, and IsNullOrEmpty/IsNullOrWhiteSpace
C# uses different text casing depending on where it's being declared. Here is a summary of the conventions:
Classes
PascalCase
Public Members
PascalCase
Private Members
_camelCase
Methods
PascalCase
Variables
camelCase
Enums
PascalCase
lists:
var list1 = new List<int>();
var list2 = new List<int> {1,2,3,4,5};
list1.Add(item:1);
list1.Remove(item:1);
list2.RemoveAt(index:3);
if list2.Contains(item:3);
var item:int = line2.Find(match:v:int => v == 3);
Dictionaries:
var dic = new Dictionary<int, string()>;
dic.Add(0, "value1");
dic.Add(1, "value2");
dic.Add(2, "value3");
foreach(var kvp:KeyValuePair<int,string> in dic)
Console.Writeline($"Key: {kvp.Key} contains: {kvp.Value}")
if (dic.TryGetValue(2, out var value:string))
console.writeline(value);
if (dic.ContainsKey(2))
dic[2] = "Updated Value";hashtables:
var table = new Hashtable
{
{0,"value1"}
{1,"value2"}
{2,"value3"}
};
foreach(DictionaryEntry entry in table)
Console.Writeline($"Entry:{entry.Key} Value: {entry.Value}");Queues:
FIFO:
var queue1 = new Queue<int>();
queue1.Enque(item:1);
queue1.Enque(item:2);
queue1.Enque(item:3);
while (queue1.TryDequeue(out var value:int))
Console.Writeline(value);LIFO:
var stack2 = new Stack<int>();
stack1.Push(item:1);
stack1.Push(item:2);
stack1.Push(item:3);
while (stack1.TryPop(out var value:int))
Console.Writeline(value);Bitwise Operators:
var rand = new Random();
var i1 = rand.Next(0,100);
var i2 = rand.Next(0,100);
Console.Writeline(i1 | i2}; // OR
Console.Writeline(i1 && i2}; // and
Console.Writeline(i1 << i2}; // shift left
Console.Writeline(i1 >> i2}; // shift right
Console.Writeline(i1 ^ i2}; // XOR If / Else:
var condition1 = true;
var condition2 = false;
var condition3 = false;
if (condition1 || condition2 && condition3) // = true - AND statement is evaluated first, followed by the OR.
if ((condition1 || condition2) && condition3) // = false
{
// do something
}
var animal = "Dog";
var sound:string = animal switch
{
"Dog" => "Woof",
"Cat" => "Meow",
_ => "who knows" // The _ => is used as a "catch all"
}
Console.Writeline(sound)
For Loops:
Statement 1 is executed one time at the start of the loop.
Statement 2 defines the condition for executing the loop code.
Statement 3 is executed after every loop.
for (var i = 0; i < 10; i++)
Console.WriteLine($"i == {i}");
var array = new[] {1,2,3,4,5};
for (var i = 0; array.Length; i++)
Console.WriteLine($"Array: {array[i]}");While Loop:
while (i < 10)
{
Console.WriteLine(i);
i++
}
// ForEach Loop
var list = new List<int> {1,2,3,4,5};
foreach(var i:int in list)
Console.WriteLine(i); Taking Arguments:
using System;
namespace Args
{
internal class Program
{
public static void Main(string[] args)
{
if (args.Length >= 2)
{
for (var i = 0; i < args.Length; i++)
Console.WriteLine($"Argument {i+1} is {args[i]}");
}
else
{
Console.WriteLine("Not Enough Arguments");
ShowUsage();
return;
}
void ShowUsage()
{
Console.WriteLine("Usage: app.exe <argv1> <argv2>");
}
}
}
}Input:
using System;
namespace ConsoleApplication1
{
internal class Program
{
public static void Main(string[] args)
{
void ShowUsage()
{
Console.WriteLine("Enter a word to echo, or enter exit to quit");
}
ShowUsage();
while (true)
{
// create a promtp
Console.Write("> ");
// read user input
var input = Console.ReadLine();
// if blank promt again
if (string.IsNullOrWhiteSpace(input))
{
ShowUsage();
continue;
}
else if (input.Equals("exit", StringComparison.OrdinalIgnoreCase))
{
Console.WriteLine("> Now exiting");
break;
}
else
{
Console.WriteLine($"You Said {input}");
}
}
}
}
}Object orientation:
using System;
using System.Runtime.Remoting.Metadata.W3cXsd2001;
var person = new Person
{
FirstName = "James",
LastName = "Hammond",
};
Console.WriteLine(person.FullName);
public
internal class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName => $"{FirstName} {LastName}";
};
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