Lambda expressions
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The document discusses lambda expressions in C# and their uses. It explains that lambda expressions allow writing methods in a more concise way and can speed up development. It provides examples of using lambda expressions with delegates having different numbers of arguments, including examples that take no arguments or return void. The document also discusses how to pronounce lambda expressions and introduces the Func and Action delegate types for lambda expressions.
![int[] source = new[] { 3, 8, 4, 6, 1, 7, 9, 2, 4, 8 }; foreach (int i in source.Where( x => { if (x % 2 == 0) return true; else if (x >= 7) return true; return false; } )) Console.WriteLine(i);Complex body](https://image.slidesharecdn.com/lambdaexpressions-100926172249-phpapp02/85/Lambda-expressions-9-320.jpg)
Lambda expressions
- 2. Why Lambda Expressions?Lambda expressions are simply methods;Give a shorter form of a methods;Speed up our work.
- 3. Using a Delegatepublic delegate int Arithmetic(int x);static public int Square(int x){ return x * x;}Arithmetic myOperation= new Arithmetic (Square);Console.WriteLine("{0}", myOperation(5));
- 4. Using an Anonymous Methodspublic delegate int Arithmetic(int x);Arithmetic myOperation= new Arithmetic ( delegate {return x * x; });Console.WriteLine("{0}", myOperation(5));
- 5. public delegate int Arithmetic(int x);Arithmetic myOperation= x => x * x;Console.WriteLine("{0}", myOperation(5));//Also with explicit input typeArithmetic myOperation = (int)x => x * x;Using a Lambda Expressions
- 6. Using λ with Two Argumentspublic delegate int Mul(int x, int y);MulmyOperation= (x, y) => x * y;Console.WriteLine("{0}", myOperation(5, 6));//Also with explicit input type MulmyOperation = (int x, int y) => x * y;Console.WriteLine("{0}", myOperation(5, 6));
- 7. Using λ with Zero Argumentspublic delegate long Ticks();Ticks myOperation= () => DateTime.Now.Ticks;Console.WriteLine("{0}", myOperation());
- 8. public delegate void DoNothing();DoNothingmyOperation= () => {};Using λ returns void
- 9. int[] source = new[] { 3, 8, 4, 6, 1, 7, 9, 2, 4, 8 }; foreach (int i in source.Where( x => { if (x % 2 == 0) return true; else if (x >= 7) return true; return false; } )) Console.WriteLine(i);Complex body
- 10. How to pronounceIf λ is a predicate x => x == “Predicate”=> spoken as “such that” Ex. x such that x state equals PredicateIf λ is a projection returns a new typex => newSomeObject(x) => Spoken as “becomes”Ex. x becomes new some object with name x.
- 11. The Func Delegate Typespublic delegate TR Func<TR>();public delegate TR Func<T0, TR>(T0 a0);public delegate TR Func<T0, T1, TR>(T0 a0, T1 a1);public delegate TR Func<T0, T1, T2, TR>(T0 a0, T1 a1, T2 a2);public delegate TR Func<T0, T1, T2, T3, TR>(T0 a0, T1 a1, T2 a2, T3 a3);publicList<T> FilterList<T>( List<T> source, Func<T, bool> filter ) {List<T> list = new List<T>();foreach( T l in source ) { if ( filter( l ) ) list.Add( l ); } return list; } List<int> list = new List<int>() { 3, 5, 7, 9, 5 };List<int> filteredList = FilterList<int>( list, x => x > 5 );
- 12. The Action Delegate Typespublic delegate voidAction();public delegate voidAction<T0>(T0 a0);public delegate voidAction<T0, T1>(T0 a0, T1 a1);public delegate voidAction<T0, T1, T2>(T0 a0, T1 a1, T2 a2);Public delegate voidAction<T0, T1, T2, T3>(T0 a0, T1 a1, T2 a2, T3 a3);void DoSomethingWithDelay(Action execute){ Thread.Sleep(1000); execute();} void F(){DoSomethingWithDelay( () => { Console.WriteLine("Done"); } );}
- 13. Any questions..?