Question

How to apply a callback to an array (apply a function to each element) in C#

Answer 1

// Using Array.ForEach with a callback

using System;

public class CallbackProgram
{
    public static void Main(string[] args)
    {
        int[] numbers = { 1, 2, 3, 4, 5 };

        // The callback is the lambda: n => Console.WriteLine(n * 2)
        Array.ForEach(numbers, n => Console.WriteLine(n * 2));
    }
}



/*
run:

2
4
6
8
10

*/

 

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Answer 2

// Using a custom callback method

using System;

public class CallbackProgram
{
    // callback
    public static void PrintSquare(int x) {
        Console.WriteLine(x * x);
    }

    public static void Main(string[] args)
    {
        int[] arr = { 1, 2, 3, 4, 5 };

        Array.ForEach(arr, PrintSquare);
    }
}


/*
run:

1
4
9
16
25

*/

 

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Answer 3

// Use LINQ Select when the callback returns a value

using System;
using System.Linq;

public class CallbackProgram
{
    public static void Main(string[] args)
    {
        int[] arr = { 1, 2, 3, 4, 5 };
        
        // Callback: n => n * 2
        var doubled_array = arr.Select(n => n * 2).ToArray();

        // Print the array after callback
        Console.WriteLine("Doubled array:");
        Array.ForEach(doubled_array, n => Console.Write(n + " "));
        Console.WriteLine();
    }
}



/*
run:

Doubled array:
2 4 6 8 10 

*/

 

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Answer 4

// Use Func<T, TResult> if the callback must return something

using System;
using System.Linq;

public class CallbackProgram
{
    public static void Main(string[] args)
    {
        int[] arr = { 1, 2, 3, 4, 5 };
        
        Func<int, int> callback = x => x + 10;

        var result = arr.Select(callback).ToArray();


        // Print the array after callback
        Console.WriteLine("Result:");
        Array.ForEach(result, n => Console.Write(n + " "));
        Console.WriteLine();
    }
}



/*
run:

Result:
11 12 13 14 15 

*/

 

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