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c# Find value in a range using lambda

Tags:

c#

find

list

range

I'm trying to find an item in a list of values based on another value using a lambda expression using the Find method. In this example I'm expecting to get back -1000, but for the life of me, I just can't come up with the proper lamda expression. If that sounds confusing I hope the code and comments below explain it better. TIA.

using System;
using System.Collections.Generic;

namespace TestingStuff {
    class Program {
        static void Main(string[] args) {
            double amount = -200;

            //The Range of values
            List<MyValue> values = new List<MyValue>();
            values.Add(new MyValue(-1000));
            values.Add(new MyValue(-100));
            values.Add(new MyValue(-10));
            values.Add(new MyValue(0));
            values.Add(new MyValue(100));
            values.Add(new MyValue(1000));

            //Find it!!!  
            MyValue fVal = values.Find(x => (x.Value > amount) && (x.Value < amount));

            //Expecting -1000 as a result here since -200 falls between -1000 and -100
            //if it were -90 I'd expect -100 since it falls between -100 and 0
            if (fVal != null)
                Console.WriteLine(fVal.Value);            
            Console.ReadKey();
        }
    }

    public class MyValue {
        public double Value { get; set; }
        public MyValue(double value) {
            Value = value;
        }        
    }
}

Mmm let me put my intentions a little clearer by specifying all the expected results.

-1000 and less to -101 should give -1000
-100 to - 11 should give -100
-10 to -1 should give -10
0 to 9 should give 0
10 to 99 should give 10
100-999 should give 100
1000 or more should give 1000

like image 991
n4rzul Avatar asked Jun 17 '26 06:06

n4rzul


2 Answers

This should work:

values.FindLast(x => amount >= x.Value);
like image 78
Julien Lebosquain Avatar answered Jun 19 '26 19:06

Julien Lebosquain


You did a logical mistake ... a value can't be > -200 AND < -200 at the same time .. U need the OR expression ( "||" )

 MyValue fVal = values.Find(x => (x.Value > amount) || (x.Value < amount));

But if you expect to get -1000 this expression is also wrong

 MyValue fVal = values.Find(x => (x.Value < amount));

Because -1000 is SMALLER than -200

EDIT : Ok I think I missunderstood your intention. But the way you want to select your value doesn't seem logical to me. Do you want the next smaller value ?

like image 25
KroaX Avatar answered Jun 19 '26 18:06

KroaX



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