All lists gets updated instead of just one element

Question

In my C# algorithm, I am using a list in which I update a specific index, but whenever I update one index all list gets updated. Please tell me what I am doing wrong.

internal class Global
    {
        public string ChromosomeName { get; set; }
        public int start { get; set; }
        public int end { get; set; }
        public int Cluster { get; set; }
        public List<int> Marks { get; set; }
        public List<int> Annotations { get; set; }
    }
var globals= new List<Global>();
var this_global = globals.Where(a => a.ChromosomeName == ChromosomeName).ToList();

((this_global[k]).Marks)[indexOfMark] += value;

This is the code of this specific part, for example when I updated (this_global[25].Marks)[0]+=37; it updated whole list and all elements of 'this_global' gets updated and each of them has a list of 'List marks' and everyone's mark list gets value '37' on index 0.

my willing result:

index 25 :

chromosomename ....
start....
end....
Cluster....
Anno....
Marks = [37,0,0] 

all other indexes apart from index 25 :

chromosomename ....
start....
end....
Cluster....
Anno....
Marks = [0,0,0] 

the actual result:

index 25 :

chromosomename ....
start....
end....
Cluster....
Anno....
Marks = [37,0,0] 

all other indexes apart from index 25 :

chromosomename ....
start....
end....
Cluster....
Anno....
Marks = [37,0,0] 

Answer 1

Looks like you're storing the same instance of List<int> with Marks property.

When you set this value It might be worth just copying the array instead, try the following

global.Marks = new List<int>(marks);