Return KeyValuePair or use out variable in C#?

Question

I have a function that needs to return two strings. I've considered two different ways to do this:

string first = "this is first";
string second = "this is second";
KeyValuePair<string, string> ReturnPair()
{
    return new KeyValuePair<string, string>(first, second);
}
string ReturnOne(out string other)
{
    other = second;
    return first;
}

I would like to use the KeyValuePair<> approach but I feel that I am misusing the purpose for which this object was created.

My questions:

1. Is there a better way to return 2 strings in this example?
2. Is there anything wrong with returning the KeyValuePair?

Answer 1

While there's nothing technically wrong with returning KeyValuePair, the thing you are returning is not conceptually a "key-value" pair. It's a simple pair.

Alternatively you can use a Tuple, which is available in .NET 4.0 or in the meantime, declare your own structure.

I normally advice against out parameters for returning tuples. Specially when you are using LINQ and functional language constructs, working with out parameters is tedious.

Answer 2

If the data belongs logically together, but one is not logically the key of the other, I would define a new type that encapsulates it.

If one is a key to the other, I would use NameValuePair.