IEnumerable<string> to string

Question

Consider this:

string test = "";
somestring.ToList().Take(50).Select(
    delegate(char x)
    {
        test += x;
        return x;
    }
);

Why is test empty after that? I don't care about the return of that actually (I know its IEnumerable<string>).

If this is all seems a mess then how can I convert the IEnumerable<char> returned by Select() to string ?

Answer 1

Because you didn't execute the query. Linq is lazy. It will be executed when you do either foreach or ToList/ToArray/ToDictionary.

and i advice to do it like that

string test = new string(somestring.Take(50).ToArray());

or even using

string test = somestring.Substring(0, 50);

More on that. Select is intended to apply some kind of transformation to every element in sequence. This operation is also known as map. If you want to produce single element from sequence it is Aggregate, aka reduce. It is not lazy, it forces execution of query.

Answer 2

(Others have explained why it doesn't work.)

Your question doesn't quite make sense at the moment - it's not clear whether you're actually dealing with an IEnumerable<char> or an IEnumerable<string>. (Your text suggests IEnumerable<string>; your code suggests IEnumerable<char>). If it's an IEnumerable<string> and you're using .NET 4, it's really easy:

string combined = string.Join("", list.Take(50));

If you're using .NET 3.5, it's still pretty easy:

string combined = string.Join("", list.Take(50).ToArray());

Obviously use something like "," if you want a delimiter between the strings.

If you're dealing with a general IEnumerable<char> then use

string combined = new string(chars.Take(50).ToArray());

If you're actually dealing with a string to start with, use Substring :)