How do I update my property in my list based on the closest key in a list

Question

I have 2 lists: list and listLookup

How do I update all the ValueToGet in list with closes KeyLookup in listLookup?

    using System.Collections.Generic;
    
    public class Program
    {
        public static void Main()
        {
            //Arrange
            //Keys needed to get ValueToGet property
            var key1 = new WidgetA{Id = 1, Key = 52};
            var key2 = new WidgetA{Id = 2, Key = 102};
            var key3 = new WidgetA{Id = 3, Key = 152};
            List<WidgetA> list = new List<WidgetA>();
            list.Add(key1);
            list.Add(key2);
            list.Add(key3);
            //Lookups
            var keyLookup1 = new WidgetB()
            {Id = 1, KeyLookup = 50, ValueLookup = "Fifty"};
            var keyLookup2 = new WidgetB()
            {Id = 2, KeyLookup = 100, ValueLookup = "One hundred"};
            var keyLookup3 = new WidgetB()
            {Id = 3, KeyLookup = 150, ValueLookup = "One hundred and fifty"};
            List<WidgetB> listLookup = new List<WidgetB>();
            listLookup.Add(keyLookup1);
            listLookup.Add(keyLookup2);
            listLookup.Add(keyLookup3);
        //Act
        /* Update all rows for ValueToGet property in list, using the closes KeyLookup in listLookup 

    Expected result:  
        
    key1: Key = 52, ValueToGet = "Fifty"
    key2: Key = 102, ValueToGet = “One hundred”
    key3: Key = 152, ValueToGet = “One hundred and fifty”       
            */
        }
    }

public class WidgetA
{
    public int Id { get; set; }

    public int Key { get; set; }

    public string ValueToGet { get; set; }
}

public class WidgetB
{
    public int Id { get; set; }

    public int KeyLookup { get; set; }

    public string ValueLookup { get; set; }
}

In SQL it would be kind of like this but finding the closest key somehow:

update list
set ValueToGet = ValueLookup
from list l1
join listLookup l2
on l1.key = l2.keyLookup

How do you define closest? What are your ranges? Is your KeyLookup list sorted? — David L, Oct 16 '22 at 14:06
int id = list.OrderBy(x => Math.Abs(x.Key - lookup)).First().Id; — jdweng, Oct 16 '22 at 14:06
Do you want [converting numbers in to words C#](https://stackoverflow.com/questions/2729752/converting-numbers-in-to-words-c-sharp)? — Olivier Jacot-Descombes, Oct 16 '22 at 14:24
@OlivierJacot-Descombes no, sorry. I want to understand how to update ValueToGet property for all rows in `list` from `listLookup` — Rod, Oct 16 '22 at 15:46
@jdweng how would i update the entire `list` for `ValueToGet` property? — Rod, Oct 16 '22 at 15:52
@DavidLCloses number in `keyLookup` to `key` for all `ValueToGet` property — Rod, Oct 16 '22 at 15:54

score 0 · Answer 1 · answered Oct 17 '22 at 07:45

If we define closest as:

Take the KeyLookup that is lower than the current Key
If there is no KeyLookup lower than the current key, take the closest higher one

Than this would solve your problem

private static void AddValueLookup(IEnumerable<WidgetA> list, IEnumerable<WidgetB> listLookup)
{
    // Ensure the collection is ordered
    using var bENumerator = listLookup.OrderBy(b => b.KeyLookup).GetEnumerator();
    
    // Get the first two values.
    // If the collection does not have at least one value, return.
    if(!bENumerator.MoveNext())
        return;
    var currentKey = bENumerator.Current;
    
    bENumerator.MoveNext();
    var nextKey = bENumerator.Current;
    
    // Ensure the collection is ordered.
    // If the list contains a key that is smaller, than the smallest one in the lookup list, 
    // it will get the next higher ValueLookup
    foreach (var a in list.OrderBy(a => a.Key))
    {
        while (a.Key > nextKey.KeyLookup)
        {
            currentKey = nextKey;
            if (bENumerator.MoveNext())
                nextKey = bENumerator.Current;
            else
                break;
        }
        a.ValueLookup = currentKey.ValueLookup;
    }
}

How do I update my property in my list based on the closest key in a list

1 Answers1