1.
//download https://www.linqpad.net/
dotnet new console -n MyFirstProgram //cannot use Console
cd MyFirstProgram
dotnet run MyFirstProgram
//or run the below if just want to build without running
dotnet build MyFirstProgram.csproj
2. All C# types fall into the following categories:
Value types, Reference types, Generic type parameters, Pointer types
3.
Indices: char secondToLast = vowels[^2];
Ranges: Ranges let you "slic" an array: char[] lastThree = vowels[2..];
C# supports "ref" and "out", "in" (cannot be modifierd by the method), "params" modifier for the parameters.
Also can have default value, named arguments
Ref Locals: int[] numbers = {0,1,2,3,4}; ref int numRef = ref numbers[2]; when we modify numRef, we modify the array element
string s1 = null;
string s2 = s1 ?? "nothing"; /s2 evaluates to "nothing"
myVariable ??= someDefault; //equivalent to if(myVariable ==null) myVariable = someDefault;
StringBuilder sb = null;
string s = sb?.ToString(); //No error; s instead evaluates to null
string s = sb?.ToString().ToUpper();//No error; s instead evaluates to null
string foo = null;
char? c = foo?[1];//c is null
switch on types: switch(x) { case int i: ... case string s:...case bool b when b == true: ... default:...}
readonly prevents change after construction: static readonly DateTime StartupTime = DateTime.Now;
const: evalution occus at compile time: public const string Message = "Hello World"; const can also be declared local to a method.
local method: you can define a method within another method.
Deconstruct has one or more out parameters.
var rect = new Rectangle(3,4);
(float width,float height) = rect; or var (width, height) = rect;
Bunny b1 = new Bunny{Name="Bo, LikesCarrots=true};
A static constructor executes once per type than once per instance. A type can define only one static constructor, and
must be parameterless.
You can also define module initializer which execute once per assembly.
Finilizers are class-only methods before the garbage collector reclaims the memory for an unreferenced object. //difference with deconstruct
partial types and partial methods
4.
int count = 123;
string name = nameof (count);
Asset a = new Asset();
Stock s = a as Stock;// s is null; no exception thrown
You can introduce a variable while using the is operator:
if (a is Stock s) Console.WriteLine(s.SharedOwned);
virtual->override
abstract->override
sealed: prevcent being override
GetType is evaluated at runtime, typeof is evaluated statically at compile time.
