Create Custom List using Lambda Expression

Question

I need to create a List of a custom type with properties of type int, int

public class CustomClass
{
   public int EmployeeID{get;set;}
   public int ClientID{get;set;}
}

Two parameters that i have to create the list is List and int

My method is

CreateCustomClassList(List<int> EmployeeIDList, int clientID}
{
List<CustomClass> lst=new List<CustomClass>();
EmployeeIDList.ForEach
  (u=>lst.Add(new CustomClass
  {
     ClientID=clientID, 
     EmployeeID=u
  });
}

I don't want to run a Loop to do this, is there any more efficient way to do this.

Your CustomClass has only private members. Is that intentional? Also your method has no return type? — Mark Byers
– Mark Byers, Commented Apr 7, 2012 at 4:38

Mark Byers · Accepted Answer · 2012-04-07 04:42:02Z

7

I'd use ToList here:

List<CustomClass> lst = EmployeeIDList
     .Select(employeeID => new CustomClass
     {
         ClientID = clientID, 
         EmployeeID = employeeID
     })
     .ToList();

It probably won't be more efficient, but it will be clearer - which in my opinion is more important.

If you really want efficiency then your best bet is probably the solution that you have already seem to have rejected - a simple loop:

List<CustomClass> lst = new List<CustomClass>(EmployeeIDList.Count);
foreach (int employeeID in EmployeeIDList) {
    lst.Add(new CustomClass
        {
            ClientID = clientID, 
            EmployeeID = employeeID
        });
}

edited Apr 7, 2012 at 4:42

answered Apr 7, 2012 at 4:37

Mark Byers

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2 Comments

Manvinder Over a year ago

Thanks Mark, Are you suggesting that a 'for loop' is efficient that a 'select'

Manvinder Over a year ago

Thanks Kevin for your valuable comment

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