CODEWITHSUNDEEP
c#listpass-by-reference
Ahmad
Ahmad

Reputation: 13436

Return reference to a generic list?

Suppose I have classes set up like this:

public abstract class GenericCustomerInformation
{
    //abstract methods declared here
}

public class Emails : GenericCustomerInformation
{
    //some new stuff, and also overriding methods from GenericCustomerInformation
}

public class PhoneNumber : GenericCustomerInformation
{
    //some new stuff, and also overriding methods from GenericCustomerInformation
}

//and more derivative classes for emails, addresses, etc ..

Then I have this function to return a specific list:

public List<GenericCustomerInformation> GetLists<T>()
{
    if (typeof(T) == typeof(Alias))
    {
        return aliases.Cast<GenericCustomerInformation>().ToList();
    }

    if (typeof(T) == typeof(PhoneNumber))
    {
        return phoneNumbers.Cast<GenericCustomerInformation>().ToList();
    }
    // .. and the same for emails, addresses, etc ..
}

Now suppose I want to add to these lists using just one function:

public void AddToList<T>(T iGenericCustomerInformation)
{
    GetLists<T>().Add((T)(object)iGenericCustomerInformation); //Doesn't work as intended. GetLists<T> seems to be returning lists as value, which is why any additions 
}

The problem is that AddToList<T> doesn't work as intended. GetLists<T> seems to be returning lists as value, which is why any additions I do are not reflected in the primary list structure ...

So how to return the list as a reference, so that I can use that reference to do list additions through other functions ?

Upvotes: 0

Views: 615

Answers (2)

Marc
Marc

Reputation: 998

Why not keep all your lists in a dictionary of lists ?

private Dictionary<Type, List<GenericCustomerInformation>> MyLists;

public List<GenericCustomerInformation> GetLists<T>()
{
    return MyLists[typeof(T)];
}

public void AddToLists<T>(GenericCustomerInformation item)
{
    GetLists<T>().Add(item);
}

Upvotes: 0

JLRishe
JLRishe

Reputation: 101758

You're already defeating the point of generics by having all those typeof()s and if statements. That's not generic at all. I'd say just put the if statement in your AddToList() method and nix the generics.

public void AddToList(GenericCustomerInformation item)
{
    Alias aliasItem = item as Alias;
    if(aliasItem != null)
    {
        aliases.Add(aliasItem);
        return;
    }

    PhoneNumber phoneNumberItem = item as PhoneNumber;
    if(phoneNumberItem != null) 
    {
         phoneNumbers.Add(phoneNumberItem);
    }
}

Upvotes: 1

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