How to populate List<int> from List<class> that contains int variable in getter

For example:

public List<Data> dataList;
public List<int> idList;

public class Data
{
  public int id;
  public string name;
}

I need to get all ‘id’ variables from ‘dataList’ into ‘idList’.
Something like that

public List<Data> dataList;
public List<int> idList
{
 get 
 {
   for (int i = 0; i < dataList.Count; i++)
   {
     idList.Add(dataList[i].id);
   }

   return idList
 }
};

But how to optimize this in a better way?

I tried to create local list, populate it with ids and then give it to the ‘idList’. But I think this method is not optimized

>Solution :

You can use Linq Select for that. select can be use to "project" from your object collection to another collection (in your case, List of int)

public List<Data> dataList;
public List<int> idList
{
   get 
   {
      return dataList.Select(x => x.id).ToList();
   };
}

More about Linq here – https://docs.microsoft.com/en-us/previous-versions/bb397926(v=vs.140)?redirectedfrom=MSDN