Code Inspection: Iteration variable can be declared with a more specific type

Consider the following class hierarchy:

public class Person
{
  public string Name { get; set; }
}
public class Child : Person
{

}
    

If we wanted to write a method that would print all of children’s names, we could define the following:

public void Print(IEnumerable<Child> children)
{
  foreach (Person p in children)
    Console.WriteLine(p.Name);
}
    

However, why should our iteration variable be Person? In fact, we could easily change it to Child and still get the same result. Note that there is a case when a more general type could not be replaced with a derived one without changes to the way code behaves. This case can occur if your iteration variable is declared to be of type dynamic.

Last modified: 08 March 2021