Question

My GUI is calling a service project that does some linq work, and returns data to my GUI. However, I am battling with the return type of the method. After some reading, I have this as my method:

public static IEnumerable GetDetailedAccounts()
 {
 IEnumerable accounts =(from a in Db.accounts
                        join i in Db.financial_institution on  
                            a.financial_institution.financial_institution_id
                               equals i.financial_institution_id
                        join acct in Db.z_account_type on a.z_account_type.account_type_id 
                               equals acct.account_type_id
                        orderby i.name
                        select new 
                             {
                              account_id = a.account_id, 
                              name = i.name, 
                              description = acct.description
                              });
            return accounts;
}

However, my caller is battling a bit. I think I am screwing up the return type, or not handling the caller well, but it’s not working as I’d hoped.

This is how I am attempting to call the method from my GUI.

IEnumerable accounts = Data.AccountService.GetDetailedAccounts();

Console.ForegroundColor = ConsoleColor.Green;
Console.WriteLine("Accounts:");
Console.ForegroundColor = ConsoleColor.White;

foreach (var acc in accounts)
  {
   Console.WriteLine(string.Format("{0:00} {1}", acc.account_id, acc.name + " " + acc.description));
  }

int accountid = WaitForKey();

However, my foreach, and the acc – isn’t working. acc doesn’t know about the name, description and id that I setup in the method. Am I at least close to being right?

Answer 1

@BrokenGlass is correct that the root of the issue is that you’re using an anonymous type. That results in you using the non-generic version of IEnumerable which doesn’t know what type the objects are.

Rather than using dynamic though (which requires .NET 4.0 which may or may not be an issue for you), I would recommend creating an actual Account class.

That way you can return an IEnumerable<Account> instead of just IEnumerable. Then you’ll be able to use the properties since it knows that it’s an Account.

Once you create the Account class your method then becomes:

public static IEnumerable<Account> GetDetailedAccounts()
{
    IEnumerable<Account> accounts = (from a in Db.accounts
                    join i in Db.financial_institution on a.financial_institution.financial_institution_id
                        equals i.financial_institution_id
                    join acct in Db.z_account_type on a.z_account_type.account_type_id equals
                        acct.account_type_id
                    orderby i.name
                    select new Account {account_id = a.account_id, name = i.name, description = acct.description});
    return accounts;

}

Then the calling code can remain the same.

I thought I should point out that var doesn’t work the way you probably think it does. The type of the variable is still determined compile-time, which means (for the most part) it’s just a shortcut. Your example would be identical to if you had used object instead of var because IEnumerable can only contain object.

If you’re working in .NET I’d recommend follow .NET naming conventions though so AccountId instead of account_id but that won’t affect whether it works or not.