List of references to strcutures

Question

Hello,

I believed that structure is a reference type.

public struct struct_A
{
     public int  struct_member1;
     public int  struct_member2;
     public int  struct_member3;
}

struct_A [] arrA_1 = new struct_A [7];
struct_A [] arrA_2 = new struct_A [7];

List<struct_A> lst_A = new List<struct_A>();

// list initialization
for (int i = 0; i < arrA_1.Length; i++)
{
    lst_A.Add(arrA_1[i];
    lst_A.Add(arrA_2[i];
}

Then I assign arrA_1[0]. struct_member2:

arrA_1[2].struct_member2 = 10;

and check lst_A[0]. struct_member2:

int check_value = lst_A[0].struct_member2

The check_value should be 10, but it isn't. Why ?

Thanks in advance.