Is it better to return null or empty collection?

Question

That\'s kind of a general question (but I\'m using C#), what\'s the best way (best practice), do you return null or empty collection for a method that has a collection as a

Answer 1

I like to give explain here, with suitable example.

Consider a case here..

int totalValue = MySession.ListCustomerAccounts()
                          .FindAll(ac => ac.AccountHead.AccountHeadID 
                                         == accountHead.AccountHeadID)
                          .Sum(account => account.AccountValue);

Here Consider the functions I am using ..

1. ListCustomerAccounts() // User Defined
2. FindAll()              // Pre-defined Library Function

I can easily use ListCustomerAccount and FindAll instead of.,

int totalValue = 0; 
List custAccounts = ListCustomerAccounts();
if(custAccounts !=null ){
  List custAccountsFiltered = 
        custAccounts.FindAll(ac => ac.AccountHead.AccountHeadID 
                                   == accountHead.AccountHeadID );
   if(custAccountsFiltered != null)
      totalValue = custAccountsFiltered.Sum(account => 
                                            account.AccountValue).ToString();
}

NOTE : Since AccountValue is not null, the Sum() function will not return null., Hence I can use it directly.