// static CalArepointer cpointer = CalculateArea;
static void Main(string[] args)
{
//CalArepointer cpointer = new CalArepointer(delegate (int r)
//{
// return 3.14 * r * r;
//});
//double Area = cpointer(20);
//more short and sweeter by using Lambda + Func
CalArepointer Cpointer = r => 3.12 * r * r;
var Area = Cpointer(20);
Func <double, double> cpoiner = r => 3.13 * r * r;
var Area2 = cpoiner(20);
Action <string> MyPrinter = y => Console.WriteLine(y);
MyPrinter("Hello");
Console.ReadLine();
}
/// <summary>
/// From Video: https://www.youtube.com/watch?v=8o0O-vBS8W0
/// </summary>
/// <param name="args"></param>
static void Main(string[] args)
{
//methode 1: Deklaration Delegate + Invoke
CalArepointer calPointer = CalculateArea;
double area = calPointer(4); //gleich wie calPointer.Invoke(4);
//methode 2: Lambda Anonymous Methods, code shorter
CalArepointer calPointer2 = new CalArepointer(
delegate(int r)
{
return(3.14 * r * r);
});
double area3 = calPointer2(4);
//methode 3: Lambda Expression, code short and sweet
CalArepointer calPointer3 = (int r) => 3.14 * r * r;
double area2 = calPointer3(4);
//methode 4: Lambda Expression + Func, code shorter and even more sweeter
Func <int, Double> calPointer4 = (int r) => 3.14 * r * r;
double area4 = calPointer4(4);
// Action Delegate (FUNC ohne Return-Value, VOID)
Action <string> myAction = y => Console.WriteLine(y);
myAction("Saliii");
// Predicate (Extension zur Func), for checking purpose
// you can replace Predicate with Func, in other words predicate delegate can be avoided.
Predicate <string> CheckGreaterThan5 = x => x.Length > 5;
CheckGreaterThan5("test"); //--> gibt 'false' zurück
///////////////////
// Warum delegates verwenden?
List <string> lString = new List <string>();
lString.Add("Sali");
lString.Add("Sali Fabian");
lString.Add("Sali Thomas");
//Find-predicate gibt hier jeden value der Liste in das Predicate rein und checkt, ob die Bedingung zutrifft. Falls ja, wird dieses zurückgegeben
lString.Find(CheckGreaterThan5); //gibt Sali Fabian zurück, weil es der erste Value ist, der dem Predicate entspricht.
lString.FindAll(CheckGreaterThan5); // gibt alle zurück
lString.Any <string>(); //true
lString.Any <string>((s) => s.Length > 5); //true
//////////////////
/// Important use of Lambda Expression: Expression Trees
/// for example (10+20) - (5 + 3)
// 10 + 20
BinaryExpression b1 = Expression.MakeBinary(ExpressionType.Add,
Expression.Constant(10),
Expression.Constant(20));
// 5 + 3
BinaryExpression b2 = Expression.MakeBinary(ExpressionType.Add,
Expression.Constant(5),
Expression.Constant(3));
// (10 + 20) - (5 + 3)
BinaryExpression b3 = Expression.MakeBinary(ExpressionType.Subtract,
b1,
b2);
// This statement will create a delegate by parsing the expression tree
int result = Expression.Lambda <Func <int> >(b3).Compile()();
// LINQ Expression Tree
var x = (from c in lString
where c.)
}
