How to match items of two list in C#?

Question

I want to get list_ID value base on List_Position. How should I do? Thanks

List<int> list_ID = new List<int> (new int[ ] { 1, 2, 3, 4, 5 });

List<string> list_Position = new List<string> (new string[ ] { A, C, D, B, E});

A = 1,

B = 4,

C = 2,

D = 3,

E = 5,

Answer 1

The best option for you at this moment is Dictionary Class with list_Position as key and list_Position as value So that you can access values based on position and wise Versa. the definition will be like the following:

 Dictionary<int, string> customDictionary= 
            new Dictionary<int, string>();

 customDictionary.Add(1,"A");
 customDictionary.Add(2,"C");
....

If you want to access value corresponds o 2 means you can use

string valueAt2 = customDictionary[2]; // will be "C"

If you want to get the key/s corresponds to the specific value means you can use like the following:

var resultItem = customDictionary.FirstOrDefault(x=>x.value=="C");
if(resultItem !=null) // FirstOrDefault will returns default value if no match found
{
   int resultID = resultItem.Key; 
}

If you still want to go with two lists means you can consider this Example Which means, Get position of the required element from the list_Position and get the element at this position in the list_ID list, Keep in mind list_ID must be greater or equal in number of elements as that of in the list_Position. The code will be like this:

string searchKey="D";
int reqPosition=list_Position.IndexOf(searchKey);
if(reqPosition!=-1)
{
    Console.WriteLine("Corresponding Id is {0}",list_ID[reqPosition]);
}
else
   Console.WriteLine("Not Found");