Teach Linq

Program.cs

// See https://aka.ms/new-console-template for more information
Console.WriteLine("Hello, World!");

var apples = new List<Apple>(){
    new Apple(){Color = "Red", Weight = 100},
    new Apple(){Color = "Green", Weight = 200},
    new Apple(){Color = "Yellow", Weight = 300},
    new Apple(){Color = "Red", Weight= 400},
    new Apple(){Color = "Blue", Weight = 500},
};

var redApples = apples.Where(a => a.Color == "Red");
System.Console.WriteLine($"There are {redApples.Count()} red apples");

var blueApples = FilterFarbeApfel(apples, "Blue");
System.Console.WriteLine($"There are {blueApples.Count()} blue apples");

var applesWith300 = FilterWeightApfel(apples, 300);
System.Console.WriteLine($"There are {blueApples.Count()} apples with 300 weight");



var redApple = apples.FirstOrDefault(a => a.Color == "Red");
System.Console.WriteLine($"There is {redApple?.Color} apple");


bool IsAppleOver300(Apple apple){
    return apple.Weight > 300;
}

var applesOver300 = FilterApfel(apples, IsAppleOver300);
applesOver300 = FilterApfel(apples, apple => apple.Weight > 300);
applesOver300 = apples.Where(apple => apple.Weight > 300).ToList();



List<Apple> FilterApfel(List<Apple> apfels, Func<Apple, bool> filter){
    var result = new List<Apple>();
    foreach(var apfel in apfels){
        if(filter(apfel)){
            result.Add(apfel);
        }
    }
    return result;
}

List<Apple> FilterFarbeApfel(List<Apple> apfels, string color){
    var result = new List<Apple>();
    foreach(var apfel in apfels){
        if(apfel.Color == color){
            result.Add(apfel);
        }
    }
    return result;
}

List<Apple> FilterWeightApfel(List<Apple> apfels, int weight){
    var result = new List<Apple>();
    foreach(var apfel in apfels){
        if(apfel.Weight == weight){
            result.Add(apfel);
        }
    }
    return result;
}

public class Apple{
    public string Color { get; set; }
    public int Weight { get; set; }
}