How to update variable in single element of struct list

Question

I`ve got a struct that includes numeral variable

public struct A
{
    public int x;
    public string y;
}

Also i have a List of a struct type:List<A> l = new List<A>()

After adding noumerus elements into the list, a want to set a value to variable y but only for the element where x=1

I am able to find the element in the list that fullfill the condition

l.Find(item => item.x == 1)

how i can to set the value of y for that specific element`? I tryed the elementary way (from my opinion) but it wrong

l.Find(item => item.x == 1).y="valueX"

Thank you in advance

Have you considered *not* using a struct, or making the struct immutable? (Yes there are ways of doing this, but I wouldn't recommend them.) — Jon Skeet, May 15 '17 at 13:00
Don't try to change values of a a struct. That's a road to nowhere. You want a class. — Ralf, May 15 '17 at 13:01
Since you have meaningless names anyway, maybe you are looking for a `Dictionary` instead. Then it's easy: `dict[1] = "valueX";` — Tim Schmelter, May 15 '17 at 13:02

score 4 · Accepted Answer · edited May 23 '17 at 12:18

This is a perfect example why using mutable strcuts is pure evil. Basically whenever your values might change you should consider to use a class instead of struct.

As of MSDN:

X DO NOT define mutable value types

The problem you got arises from the fact that structs are value-types which get copied whenever passed to or returned from a member - in your case List.Find. Thus any updates to the instance you recieved via Find won´t be reflected to the instance within the list. You could strangly bypass this by using an array instead of a list, but that´s also a bad idea as it hides the actual problem.

How to update variable in single element of struct list

1 Answers1