How to achieve multiple return values in C# like python style

Question

I have a python script:

def f():
    a = None
    b = None
    return (a, b)


a, b = f()

It's so easy to achieve multiple return values in python. And now I want to achieve the same result in C#. I tried several ways, like return int[] or KeyValuePair. But both ways looked not elegant. I wonder a exciting solution. thanks a lot.

The Tuple class is a little more elegant, msdn.microsoft.com/en-us/library/system.tuple.aspx — Maarten
– Maarten, Commented Jan 25, 2013 at 9:07
Are multiple return values a good and desirable thing? Should functions be able to return anonymous types? — Jodrell
– Jodrell, Commented Jan 25, 2013 at 9:21
You might try F#, which supports this: let f() = (14, 29) then let (a, b) = f() — phoog
– phoog, Commented Jan 25, 2013 at 9:24
@Jodrell they are very useful indeed. F#, for example, handles TryParse much more concisely than C#, because it returns out parameters as part of a tuple: let (success, result) = Int32.TryParse(someString) — phoog
– phoog, Commented Jan 25, 2013 at 9:25
@phoog, on consideration, I'm inclined to agree, as long as the types in the tuple are defined, unlike the OPs example. — Jodrell
– Jodrell, Commented Jan 25, 2013 at 9:30

D J · Accepted Answer · 2013-01-25 09:26:34Z

6

Use Tuple class.

  public Tuple<int,int> f()
  {
        Tuple<int,int> myTuple = new Tuple<int,int>(5,5);
        return myTuple;
  }

edited Jan 25, 2013 at 9:26

answered Jan 25, 2013 at 9:10

D J

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Comments

Aasmund Eldhuset · Accepted Answer · 2013-01-25 09:07:27Z

3

Unfortunately, C# does not support this. The closest you can get is to use out parameters:

void f(out int a, out int b) {
    a = 42;
    b = 9;
}

int a, b;
f(out a, out b);

answered Jan 25, 2013 at 9:07

Aasmund Eldhuset

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2 Comments

Jun HU Over a year ago

does it like the reference parameter passing？

Aasmund Eldhuset Over a year ago

@JunHU: I don't understand - what is "it"?

Jodrell · Accepted Answer · 2013-01-25 09:34:50Z

2

You can obviously do

object F(out object b)
{
    b = null;
    return null
}

object b;
var a = F(out b)

but better to use Tuple with a functional style,

Tuple<object, object> F()
{
    return Tuple.Create<object, object>(null, null);
}

var r = F();
var a = r.Item1;
var b = r.Item2;

but, since in c# you can be explicit, why not define your return type.

struct FResult
{
    public object A;
    public object B;
}

FResult F()
{
    return new FResult();
}

var r = F();
var a = F.A;
var b = F.B;

This seems like a small price to pay for the semantic benefits.

edited Jan 25, 2013 at 9:34

answered Jan 25, 2013 at 9:11

Jodrell

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1 Comment

phoog Over a year ago

F# is type safe, but you can also have let f x = (x*2, x*x) and let (a, b) = f 5, which assigns the values 10 and 25 to a and b, respectively.

relatively_random · Accepted Answer · 2017-08-02 13:58:13Z

0

This feature is available in C#7 with .Net 4.7.

private (string a, string b) f()
{
    return (a: null, b: null);
    // or simply: return (null, null);
}

var (a, b) = f();

answered Aug 2, 2017 at 13:58

relatively_random

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