Does C# support multiple return values?

Question

The noob here again. This is a very basic question, and if what I am thinking of doing is complicated/involved, then I don't expect you to go into detail... I've read that this may involve structs or hash or some other scary procedure I've not gotten to yet. If so, I'm sure it'll get me soon.

Working on learning classes, methods, and return values.

I'd like to have my class/method return Current Hour and Minute. Simple enough, really. Is this constructed correctly, or properly? My class:

class MyClass
        {
        public int GetHour (int hr, int min)
            {
            DateTime dt = DateTime.Now;

            int hour = dt.Hour;
            int minute = dt.Minute;

            return hour;
            return minute;

            }
        }

And, calling it from Main(): Getting some errors (No overload for method and Unreachable code detected)

static void Main ( string[] args )
            {
            MyClass mc = new MyClass ();
            Console.WriteLine ("Hour: {0} \n Minute: {1}", mc.GetHour());

            Console.ReadLine ();
            }

Question is: Am I Close?! :-) or not? Thanks! dong

Answer 1

C# does not support multiple return values so in this case you should return a DateTime struct which is the idiomatic approach. The client code can simply ignore the properties that they don't care about. You could create your own simple struct but it really isn't worth the effort.

Answer 2

Yeah, you can only return one 'thing' from method in C#.

The other problem you have is you are calling a method without any parameters. The things in the brackets:

public int GetHour (int hr, int min) // here
{
}

Are parameters. And you need to specify them when calling the method, like so:

mc.GetHour(1, 2);

But of course, in your case, it doesn't make sense to do this.

To answer the general question of: "How do I return more than one thing?" You encapsulate it in a class, set the properties, and return that class. It so happens, in the example you've given, the DateTime class does just that.

Hope this is helpful.

Answer 3

Sorry, you can't do that. You'd be better served returning an array or an object. You could return the DateTime object and use it.

Also as stated, your function signature wasn't being called properly.

class MyClass
        {
        public int[] GetHour ()
            {
            DateTime dt = DateTime.Now;

            int hour = dt.Hour;
            int minute = dt.Minute;

            return new int[]{hour, minute};
            }
        }

static void Main ( string[] args )
            {
            MyClass mc = new MyClass ();
int[] temp = mc.GetHour();
            Console.WriteLine ("Hour: {0} \n Minute: {1}", temp[0], temp[1]);

            Console.ReadLine ();
            }

Answer 4

C# doesn't support the idea of directly returning multiple values from a method in that fashion. However there are a couple of ways to create methods which return multiple values. The first is to use ref / out parameters.

public void GetHourMinute(out int hour, out int minute) { 
  var now = DateTime.Now;
  hour = now.Hour;
  minute = now.Minute;
}

The second is to create a wrapper type which encapsulates the two values. Starting in 4.0 this can be made a bit easier by using the Tuple type.

public Tuple<int,int> GetHourMinute() {
  var now = DateTime.Now;
  return Tuple.Create(now.Hour, now.Minute);
}

Answer 5

1: You can't have two returns. Once the compiler reaches the return statement, the operation of the method is finished.
2: Why would you want your method to receive parameters if you don't use them? DateTime.Now gives you the current time, if you'll think of yourself as that method - what do you need in order to complete your task? Nothing.

So, practical tips:
1. Actually, the DateTime does what you need better than your method.

Console.WriteLine ("Hour: {0} \n Minute: {1}", DateTime.Now.Hour,DateTime.Now.Minute);

Would have been better,
but let's ignore that and consider it an exercise in classes.

2 Returning two values is against the concept of a method - a method returns one thing (there are exceptions as out ref, but we'll ignore them).
You can actually see that in your own code - your method name is GetHour not GetHourAndMinutes. I don't think I've ever seen a method's name with the word "and" - a method does only one thing.

Answer 6

I suggest you return the DateTime object. Then in your main method you call Hour and Minute properties.

Answer 7

You cant return multiple value. TimeSpan is exactly what you are looking for. Create an object of that with hour, minute and even second that you want to capture and return it.

Come to think about it, for what you need above, you dont even have to write the method above. Just use DateTime.Now.TimeOfDay directly in your code

Answer 8

As mentioned by @ChaosPandion, in that specific case you would return a DateTime struct.

In general, however, you would have the following options:

Using out parameters

This is a simple way that will usually always work. However, it is a bit clunky, as the result is returned where you usually would expect the function arguments to be passed and the method signature might get lengthy and hard to refactor.

public void GetTime(out int hr, out int min) 
{ 
    DateTime dt = DateTime.Now;
    hr = dt.Hour;
    min = dt.Minute;
}

static void Main(string[] args)
{
     // declare variables for out parameters first
     int hour, minute;
     GetTime(out hour, out minute);
}

Using an array

This is a simple method that works well if the values to be returned have the same type.

public int[] GetTime() 
{ 
    DateTime dt = DateTime.Now;
    return new[] { dt.Hour, dt.Minute};
}

Using a property bag (A property bag is a simple class which only has properties)

This is very convenient and allows easy modification of the type and number of returned values later on without changing the method signature.

class A
{ 
     int Prop1 { get; set; }
     int Prop2 { get; set; }
}

public A SomeMethod()
{
    return new A() { Prop1 = 1, Prop2 = 2 }
}    

Using a Tuple

In C# 4.0 (requires VS 2010) you can use the Tuple<T1, T2, ...> class:

public Tuple<int, int> GetTime() 
{ 
    DateTime dt = DateTime.Now;
    return Tuple.Create(dt.Hour, dt.Minute);
}

Answer 9

You can't return twice, only once.
Several return values at once require lambda expressions, and AFAIK, only Python is capable of that.
Syntax there goes like this:

return x, y

So maybe you should try IronPython, and then decompile to C#.

In C#, there are exactly two ways to return more than one value:
1. Use arguments as call by reference, that way you can assign 3 variables and then return.
2. Use some kind of struct/class/array/tuple/vector and place your multiple values into it.

Call by reference is something like this:

public static void xxx(ref var1, ref var2, ref var3) { var1 = 123; var2 = 456; var3 = 789; return; }

then you do:

int a =1;
int b=2;
int c=3;

xxx(ref a, ref b, ref c);

Console.WriteLine(a.ToString());
Console.WriteLine(b.ToString());
Console.WriteLine(c.ToString());

Answer 10

In C# a method can return multiple times, if you use yield return format.

using System.Collections.Generic;

namespace YieldReturn
{
    class Program
    {
        public static void Main(string[] args)
        {
            MyClass mc = new MyClass();
            IEnumerator<int> enu = mc.GetHour().GetEnumerator();
            enu.MoveNext();
            int hour = enu.Current;
            enu.MoveNext();
            int min = enu.Current;
            Console.WriteLine("Hour {0} min {1}", hour, min);
            Console.ReadKey(true);
        }
    }

    class MyClass
    {
        DateTime dt;

        public MyClass()
        {
            dt = DateTime.Now;
        }
        public IEnumerable<int> GetHour()
        {
            int hour = dt.Hour;
            int minute = dt.Minute;
            yield return hour;
            yield return minute;
        }
    }
}

Gives "Hour 8 min 50"

Answer 11

The question I would like to ask you is why do you want to return multiple values? Returning multiple values for me means having multiple responsibilities in the function and that should be a big don't since it is violating SRP. But, if those return values are related maybe they make an object that you're missing and should be created instead? Or a list with one type of object.

So for short. Why? Encapsulate your return values in ONE object? Don't do multiple things in one function.

EDIT: In your case I wouldn't even wrap your functionality in a function just write:

static void Main ( string[] args )
        {
        MyClass mc = new MyClass ();
        DateTime now = DateTime.Now;
        int hour = now.Hour;
        int min = now.Minute;
        Console.WriteLine ("Hour: {0} \n Minute: {1}", hour, min);

        Console.ReadLine ();
        }

And your function name GetHour doesn't do what the function says... if it says GetHour it should return the hour and not the hour plus the minute.