Return 2 values from a function?

Question

I have an object that represents a scheduled payment. My database has a list of these payments, but I have one instance of a payment.

I need to write a method that gets the next payment after the one I have, as well as the previous date of the previous payment.

I'd like to write a method that return the two dates. But the return type of 'DateTime' only allows for one. I could return a List<DateTime> but that seems strange and ma be ambiguous. Which is the previous and which is the next?

I can also create a DTO object that has:

DateTime previousPayment {get; set;}
DateTime nextPayment {get; set;}

Tuple<DateTime, DateTime> might be another options, but it too is ambiguous. Unless I can name the properties of it?

But - is there a better way to allow for a method to return two dates? Anonymous types or something?

For multiple return you can user class object or generic list or array — Anik Islam Abhi, Nov 02 '14 at 04:59
Also look at this duplicate question: http://stackoverflow.com/q/748062/2557263 — Alejandro, Nov 02 '14 at 05:09

Levi Fuller · Answer 1 · 2015-08-11T17:44:06.000

Use the "ref" modifier. (You may use "out" instead if you do not need to read the variable before it is assigned)

public void GetNextPayment(ref DateTime previousPayment, ref DateTime nextPayment){
    // do stuff here
}

Usage:

DateTime previousPayment = DateTime.Now(); //Example
DateTime nextPayment = DateTime.Now(); // example
GetNextPayment(ref previousPayment, ref nextPayment); // Forgot to add "ref" when calling it

previousPayment and nextPayment will be modified in the function and maintain the value.

Update with Dictionary

As Anik mentioned, it might be better to use a Dictionary;

public Dictionary<string,DateTime> GetNextPayment(DateTime previousPayment, DateTime nextPayment){
    // modify payments
    Dictionary<string,DateTime> myDict = new Dictionary(string, DateTime);
    myDict.Add("PreviousPayment", [date]);
    myDict.Add("NextPayment", [date]);
    return myDict;
}

Use Class

Ilya. N. mentioned to use a class. I would have to agree with this if you're going to have lots of payment objects going to be used more than once. But I firmly believe it's better to give you all the tools available at your disposal because you never know when you might want to use out parameters or Dictionaries.

public class Payment {
    public string Name {get;set;}
    public DateTime previousPayment {get;set;}
    public DateTime nextPayment {get;set;}

    public GetNextPayment(){
        // code to get the next payment
        this.previousPayment = //whatever
        this.nextPayment = //whatever
    }
}

If you only have ONE payment you are going to be using, like ever. (good to future proof with a class), then you might use a method or dictionary.

right, out parameters can really be thought of as pass by reference. C++ ftw! — Freestyle076, Nov 02 '14 at 05:07

IKnowledge · Answer 2 · 2014-11-02T05:05:40.410

1

Why not simply return a class?

public class DateCombo {
DateTime PreviousPayment {get; set;}
DateTime NextPayment {get; set;}

}

edited Nov 02 '14 at 05:05

answered Nov 02 '14 at 04:59

IKnowledge

221
3
12

That was what I mentioned in my answer. Might be the only clean way. – Craig Nov 02 '14 at 05:00
Although I still prefer the class, Dictionary can be used as well. – IKnowledge Nov 02 '14 at 05:03
I like this better than either the Tuple answers or the `out` answers. Maybe I'm just prejudiced against out, but I find `out` appears so infrequently within the C# built-ins that it doesn't fit as well. – furkle Nov 02 '14 at 05:09

score 1 · Answer 3 · answered Nov 02 '14 at 04:59

1

Besides the two options you listed, there are two more:

Return a Tuple<DateTime, DateTime>
Use out parameters

answered Nov 02 '14 at 04:59

Matt Jacobi

864
7
17

Yeah, I just added the Tuple... I'm maybe thing 'out' is the way to go, as they're named. – Craig Nov 02 '14 at 05:00
1

Bur remeber - do not use `Tuple` for public interface - rather for internal/privte. – Nov 02 '14 at 07:09

score 0 · Answer 4 · answered Nov 02 '14 at 05:08

try this ...

private void Form1_Load(object sender, EventArgs e)
    {
        DateTime previousPayment =new DateTime();
        DateTime nextPayment=new DateTime();
        getdate(ref previousPayment, ref nextPayment);
    }
    public void getdate(ref  DateTime previousPayment, ref DateTime nextPayment)
    {
        previousPayment = System.DateTime.Now;
        nextPayment = System.DateTime.Now.AddDays(1);

    }

Return 2 values from a function?

4 Answers4