CODEWITHSUNDEEP
c#generics
Ciarán Bruen
Ciarán Bruen

Reputation: 5341

Returning a generic List from a function

As an exercise I'm trying to create a function that returns a generic list from another generic list that's passed to the function. The list passed in could be of either int or string, and I want to return a list of all members of the passed in list that have an even number of characters. The way I'm doing it isn't correct and it doesn't compile, but I want to know why. (I'm using an anonymous method which I know can be replaced with a Lambda expression, but I'd like to know first why it's not working).

List<T> GetEvens(List<T> list)
{
    List<T> newList = 
        list.FindAll(delegate(T t)
        {return t.ToString().Length() % 2 == 0;});

    return newList;
}

I'm getting an error on lines 3 and 4 saying "The type or namespace name 'T' could not be found". Why doesn't the function recognise 'T'? I know the function will work if I make it a specific return type such as string, but then I'd have to create a separate function for every type I wanted to use which doesn't seem very efficient.

Upvotes: 0

Views: 7449

Answers (3)

corvuscorax
corvuscorax

Reputation: 5930

Try List<T> GetEvens<T>( ... )

Upvotes: 4

slugster
slugster

Reputation: 49974

Length is a property, not a method, so remove the brackets from it.

Upvotes: 0

Darin Dimitrov
Darin Dimitrov

Reputation: 1038720

The reason is that there's no Length method. It's a property so you don't need the parentheses:

return t.ToString().Length % 2 == 0;

But to make you code shorter:

public List<T> GetEvens(List<T> list)
{
    return list.FindAll(t => t.ToString().Length % 2 == 0);
}

Upvotes: 0

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