C# methods with multiple return parameters

Question

Is there a need for multiple return parameters in c#/.net?

public string, string GetFirstNameAndLastName(int id)
{
    var person = from p in People
                 where p.Id = id
                 select p;
    return(p.FirstName, p.LastName);
}

Usage:

public void Main(string[] args)
{
    string firstName, lastName;
    (firstName, lastName) = GetFirstNameAndLastName(1);

    Console.WriteLine(firstName + ", " + lastName);
}

Why do you need to return the firstName & lastName as separate values? Shouldn't they be represented in a Person instance? FirstName and LastName are properties of a Person object. — Devendra D. Chavan, Apr 06 '11 at 04:44

James Webster · Answer 1 · 2011-04-06T05:16:19.447

7

You can achieve this in a lightweight fashion using Tuple in C# 4.0

public Tuple<string, string> GetFirstNameAndLastName(int id)
{
   var person = from p in People
             where p.Id = id
             select p;
   return new Tuple<string, string>(p.FirstName, p.LastName);

   // OR
   // return Tuple.Create(p.FirstName, p.LastName);
}

System.Tuple also has the benefit of interoperating with F# native tuple type (well, it IS F#'s native tuple type, there just happens to be F#-specific syntax support for declaring tuples and functions that return them).

Given the existence of multiple approaches here: System.Tuple, multiple out parameters or returning a POCO with FirstName and LastName properties, I suspect that Anders Hejlsberg is probably not going to add explicit support for multiple return values.

edited Apr 06 '11 at 05:16

answered Apr 06 '11 at 04:34

James Webster

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@James I believe you can use Tuple.Create(p.FirstName, p.LastName) to avoid having to specify the generic parameters. – Matt Hamilton Apr 06 '11 at 04:35
Yep, just updated to reflect that ;-) – James Webster Apr 06 '11 at 04:35
@James: The only problem with Tuples is the nasty `.Item1` and `.Item2` properties to get the components. Makes the code slightly less readable. – Andrew Cooper Apr 06 '11 at 04:37
... especially since they start counting from 1, an not from 0 like common for arrays f.e. – user492238 Apr 06 '11 at 04:40
`System.Tuple` also has the benefit of interoperating with F# native tuple type (well, it IS F#'s native tuple type, there just happens to be F#-specific syntax suppotr for declaring tuples and functions that return them. – James Webster Apr 06 '11 at 04:56
I know abut Tuple but it's so ugly to use. It gives no indication to the code using the method of what the tuple contains. – Jonathan Parker Apr 07 '11 at 00:49

score 5 · Answer 2 · edited Apr 06 '11 at 05:35

5

No, just use out parameters.

public void GetFirstNameAndLastName(int id, out string first, out string last)
{
    var person = from p in People
                 where p.Id = id
                 select p;
    first = p.FirstName;
    last = p.LastName;
}

edited Apr 06 '11 at 05:35

James Webster

4,046
29
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answered Apr 06 '11 at 04:33

Jonathan Wood

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your function signature looks suspicious – user492238 Apr 06 '11 at 04:41
I don't see the reason for the other answers this one seems obvious, simple, and straightforward. – Larry Watanabe Apr 06 '11 at 04:44
@user492238: Yup, got a little carried away with copy and paste there. :-) – Jonathan Wood Apr 06 '11 at 05:36

score 4 · Accepted Answer · edited May 23 '17 at 10:24

4

As suggested by @James Webster you can use tuple or you can use dynamic and ExpandoObject

class Program
{
    static void Main(string[] args)
    {
        var d = GetUserDynamic();
        Console.WriteLine("{0}.{1}", d.FirstName, d.LastName);
    }

    private static dynamic GetUserDynamic()
    {
        dynamic d = new ExpandoObject();
        d.FirstName = "amandeep";
        d.LastName = "tur";
        return d;
    }
}

edited May 23 '17 at 10:24

Community

1
1

answered Apr 06 '11 at 04:40

TheVillageIdiot

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I like this solution. It's simple and easy to understand. The obvious downside is no static type checking. – Jonathan Parker Apr 07 '11 at 01:11
@Jonathan Parker if you have few things to return then you should not worry too much. – TheVillageIdiot Apr 07 '11 at 11:59

score 1 · Answer 4 · answered Apr 06 '11 at 04:37

No. You should return a more useful data type like a class if the elements are related.

public MyPersonClassGetFirstNameAndLastName(int id)
{
    var person = from p in People
                 where p.Id = id
                 select p;

    MyPersonClassreturnValue = new MyPersonClass;
    returnValue.FirstName = p.FirstName; 
    returnValue.LastName= p.LastName;
    return returnValue;
}

score 0 · Answer 5 · answered Apr 06 '11 at 04:39

Next to the possibilities pointed out in other answers, there is are more ways to archieve this:

create your own return type (similar to the Tuple method) and return an instance of it
ref parameters: http://msdn.microsoft.com/en-us/library/14akc2c7%28v=vs.80%29.aspx

score 0 · Answer 6 · answered Apr 06 '11 at 04:40

Depends on the situation. In your case you could return the whole person record back,

public string, string GetFirstNameAndLastName(int id)
{
    var person = from p in People
             where p.Id = id
             select p;
    return person;
}

or if the situation required it you could create your own data type.

score -1 · Answer 7 · answered Apr 06 '11 at 04:34

You can do what you want like this:

public void GetFirstNameAndLastName(int id, out string firstName, out string lastName)
{
    var person = from p in People
                 where p.Id = id
                 select p;
    firstName = p.FirstName;
    lastName =  p.LastName;
}

and then call it like this:

public void Main(string[] args)
{
    string firstName, lastName;
    GetFirstNameAndLastName(1, out firstName, out lastName);

    Console.WriteLine(firstName + ", " + lastName);
}

Who did a -1 on this? I am not a big fan of out parameters, but I would like to hear from the down voter. — peter, Apr 07 '11 at 23:21

C# methods with multiple return parameters

7 Answers7