Casting new tuple to old one gives compilation error

Question

With the code below,

class Program
{
    static void Main(string[] args)
    {
        Tuple<int, int> test = TupleTest();

    }

    static (int, int) TupleTest()
    {
        return (1, 2);
    }

I am getting following compile time error.

Error CS0029 Cannot implicitly convert type '(int, int)' to 'System.Tuple < int, int >'

Does it mean the new version of Tuple is not compatible with the old version implicitly? Or am I doing something wrong here?

The "new tuple" is a different type called [`System.ValueTuple`](https://msdn.microsoft.com/en-us/library/system.valuetuple(v=vs.110).aspx) (see [this question](http://stackoverflow.com/questions/41084411/whats-the-difference-between-system-valuetuple-and-system-tuple) for a discussion of the differences) and AFAIK there are no plans to make it implicitly convertible to `System.Tuple` — UnholySheep, Apr 23 '17 at 21:58
As Matej answered below you should use the extension methods (`ToTuple`). The reason those cannot be implemented as user-defined conversions is that we need them to go above arity 7. — Julien Couvreur, May 28 '17 at 21:26

Matěj Pokorný · Accepted Answer · 2017-10-31T10:16:46.813

18

Yeah, you should use extension method ToTuple. So in your example...

class Program
{
    static void Main(string[] args)
    {
        Tuple<int, int> test = TupleTest().ToTuple();

    }

    static (int, int) TupleTest()
    {
        return (1, 2);
    }

edited Oct 31 '17 at 10:16

answered Apr 23 '17 at 22:25

Matěj Pokorný

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score 3 · Answer 2 · edited May 02 '23 at 17:51

3

Use ValueTuple instead:

ValueTuple<int, int> test = TupleTest();

Use the ToTuple extension method (ToValueTuple is also available):
```
Tuple<int, int> test = TupleTest().ToTuple();
```

edited May 02 '23 at 17:51

KyleMit

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answered Oct 17 '18 at 22:51

Shimmy Weitzhandler

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Casting new tuple to old one gives compilation error

2 Answers2