Delegates and Lambda Expressions

Rupal Patel

Hi Friends, I was just wondering in this code why was I able to pass the Delagate in as a parameter for the lambda expression. I thought that a delegate was used as a pointer to a method or function, and then pass the Delegate as a parameter. Thanks !

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace Delagate
{
delegate bool MeDelagate(int n);
class Program
{
//static bool LessThanFive(int n) { return n < 5; }
// static bool LessThanTen(int n) { return n < 10; }
//static bool GreaterThanThirteen(int n) { return n > 13; }
static void Main(string[] args)
{
int[] numbers = new[] { 2, 7, 3, 7, 9, 17,5, 1, 8, 1700 };
IEnumerable<int> result = RunNumbersThroughGauntlet(numbers, n => n > 1500);
foreach (int n in result)
Console.WriteLine(n);
}
static IEnumerable<int> RunNumbersThroughGauntlet(IEnumerable<int> numbers, MeDelagate gauntlet)
{
foreach (int number in numbers)
if (gauntlet(number))
yield return number;
}
}
}

3 Replies

Know the answer? Post it — somebody with the same question will find it here.

Sreekanth Reddy7y ago
Accepted answer
Hi Rupal,

Yes, your doubt is valid.

To get understand about this theme, We should be aware of knowing the concepts of DELIGATES, ANONYMOUS METHODS & LAMBDA EXPRESSIONS.
Most of us(including me) initially feels that lambda expressions are unique and separate concepts.
But, we must know that they(lambda expressions) exists only because of existance of DELGATES.
If you knew all those concepts, I hope you can understand my below statement, Else please gothrough those concepts and think about this :
"As lambda expressions are simplified versions of theory for the deligates, we can pass the lambda too"
If you are not interested with lambda...
Then pass the deligate object related method.

If it helps, mark as answer.
Thank you.
Rupal Patel7y ago
I guess I meant where in the code is the lambda expression ever associated with the delegate?
Jignesh Kumar7y ago
Hi Rupal,

Delegate we can use as parameter as well, Here this example delegate used as parameter and its read off hard code condition check here. Its based on your ladmda expression you can wirte to pass delegate.

Lets take below example where first parameter is list and second is your condtion so if you want to change you condition you can there will be no change in your code of this method RunNumbersThroughGauntlet().
Lets you want to get number less then 100 then just you lamada expression changes with second parameter n => n <100. So here lamda expression is used as parameter and it will help us to remove had coded condition.
RunNumbersThroughGauntlet(numbers, n => n > 1500);