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

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

CodePudding user response：

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