What's the purpose of the Tuple(T1)/Singleton in .net?

Question

One of the Tuple Types in .net 4 is a Single-Element Tuple. I just wonder what the purpose of this struct is?

The only use I saw is when using in the 8+ Tuple as it

Answer 1

Although this is an old thread, I was preparing an answer for Why use a 1-tuple, Tuple in C#? , which is now marked as a duplicate.

One possible usage of a 1-Tuple, is to return a null instance if there is no value, but that null of the item value itself, does not mean there is no result.

For example (not a very good real life example, but hopefully it conveys the point)

    static List List = new List {"a", "b", null, "c"};

    static Tuple GetItemAtIndex(int index)
    {
        if (index < 0 || index >= List.Count)
            return null;
        return Tuple.Create(List[index]);
    }

The calling code would know that when the tuple itself is null, it did not exist in the list, but if Item1 is null, there actually was a null item in the list. Of course in this example, plenty of better workarounds exist, but it could also apply to a result out of a database: no result found or a result that is null.

Extending that same logic, a Tuple can be used to easily create generic methods that can return null for any type. For example

    static Tuple GetSomething(RecType rec, Func fn)
    {
        if (rec == null) return null;
        //extra example, access would be checked by something like CheckCurrentUserAccess(rec)
        bool AccesDenied = true;
        if (AccesDenied) return null; //sometimes you don't want to throw an exception ;)

        return Tuple.Create(fn(rec));
    }

You could return Nullable, but that would only work for structs, where this works with any type, albeit int, string, int?, MyClass, etc