Equivalent of Tuple (.NET 4) for .NET Framework 3.5

Question

Is there a class existing in .NET Framework 3.5 that would be equivalent to the .NET 4 Tuple?

I would like to use it in order to return several values from a method, rather than create a struct.

Moir

Short answer is No. – Idiosyncrasy

Se my answer for a simple implementation of the Tuple class for two items. – Blaze

The more I use tuples, the more I like dedicated structs -- the ambiguousness of .Item1, .Item2 is kind of annoying when you can't remember what's in there.. – Libratory

Instead of a struct, why not return an instance of a class with the public members you want to return? I think that makes everything a little more self-documenting. As would a struct, but I personally prefer classes to structs. – Fart

Daft question but whats wrong with KeyValuePair<T1, T2> ?? – Preiser

@Wardy KeyValuePair implies that there is a value associated to a key. Not what I wanted at the time. – Moir

@Wardy and importantly it is a struct so can't be used with as for example. – Previse

Answer 1

No, not in .Net 3.5. But it shouldn't be that hard to create your own.

public class Tuple<T1, T2>
{
    public T1 First { get; private set; }
    public T2 Second { get; private set; }
    internal Tuple(T1 first, T2 second)
    {
        First = first;
        Second = second;
    }
}

public static class Tuple
{
    public static Tuple<T1, T2> New<T1, T2>(T1 first, T2 second)
    {
        var tuple = new Tuple<T1, T2>(first, second);
        return tuple;
    }
}

UPDATE: Moved the static stuff to a static class to allow for type inference. With the update you can write stuff like var tuple = Tuple.New(5, "hello"); and it will fix the types for you implicitly.

Blaze

it doesn't have to be more involved, it depends on your business needs. The question says: "I would like to use it in order to return several values from a method, rather than create a struct." and you don't need comparison and equality for that. – Blaze

One, you haven't provided Equals implementation which .NET 4.0 tuples give you, two, you're talking about type inference not implicit conversion in the last case. – Wernick

@nawfal, thank you regarding the type inference. Regarding the equals implementation you can need my comment. That might not be needed depending on the business needs and I answered the specific questions and did not write a complete implementation as it is implemented in .NET 4.0. Also, I didn't say that this was a complete implementation of tuples. – Blaze

Hmmm. The q is about .NET 4.0 tuple equivalent. Not to nitpick, but equatability of tuples is something beginners usually overlook. That one aspect is actually worth mentioning. – Wernick

@nawfal, reading the whole question: "I would like to use it in order to return several values from a method, rather than create a struct." He doesn't mention anything about equality between tuples and if that's an issue it's not that hard to add. But again, you are totally right about the inference part and I have updated the answer. – Blaze

since Tuples are regarded values (hence the private setters), shouldn't this be rather a struct than a class? – Callimachus

FYI, the Tuple class appears to have changed in .NET 4.5; the properties arecalled Item1 and Item2 instead of First and Second. – Sociology

For complete, and well-maintained, solutions see answer with link to Mono and answer with link to NetLegacySupport – Landry

Answer 2

I'm using this in my pre-4 projects:

public class Tuple<T1>  
{ 
    public Tuple(T1 item1) 
    { 
        Item1 = item1; 
    }   

    public T1 Item1 { get; set; }  
} 

public class Tuple<T1, T2> : Tuple<T1>  
{ 
    public Tuple(T1 item1, T2 item2) : base(item1) 
    { 
        Item2 = item2; 
    } 

    public T2 Item2 { get; set; }  
} 

public class Tuple<T1, T2, T3> : Tuple<T1, T2>  
{ 
    public Tuple(T1 item1, T2 item2, T3 item3) : base(item1, item2) 
    { 
        Item3 = item3; 
    } 

    public T3 Item3 { get; set; }  
} 

public static class Tuple  
{ 
    public static Tuple<T1> Create<T1>(T1 item1) 
    { 
        return new Tuple<T1>(item1); 
    } 

    public static Tuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2) 
    { 
        return new Tuple<T1, T2>(item1, item2); 
    } 

    public static Tuple<T1, T2, T3> Create<T1, T2, T3>(T1 item1, T2 item2, T3 item3) 
    { 
        return new Tuple<T1, T2, T3>(item1, item2, item3); 
    }  
}

Rebekahrebekkah

Why do you need Tuple<T1>? Is that even a tuple? – Blaze

Answer 3

In the event that you need them to have feature-parity with .Net 4.0 (primarily comparisson):

static class Tuple
{
    public static Tuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2)
    {
        return new Tuple<T1, T2>(item1, item2);
    }
}

[DebuggerDisplay("Item1={Item1};Item2={Item2}")]
class Tuple<T1, T2> : IFormattable
{
    public T1 Item1 { get; private set; }
    public T2 Item2 { get; private set; }

    public Tuple(T1 item1, T2 item2)
    {
        Item1 = item1;
        Item2 = item2;
    }

    #region Optional - If you need to use in dictionaries or check equality
    private static readonly IEqualityComparer<T1> Item1Comparer = EqualityComparer<T1>.Default;
    private static readonly IEqualityComparer<T2> Item2Comparer = EqualityComparer<T2>.Default;

    public override int GetHashCode()
    {
        var hc = 0;
        if (!object.ReferenceEquals(Item1, null))
            hc = Item1Comparer.GetHashCode(Item1);
        if (!object.ReferenceEquals(Item2, null))
            hc = (hc << 3) ^ Item2Comparer.GetHashCode(Item2);
        return hc;
    }
    public override bool Equals(object obj)
    {
        var other = obj as Tuple<T1, T2>;
        if (object.ReferenceEquals(other, null))
            return false;
        else
            return Item1Comparer.Equals(Item1, other.Item1) && Item2Comparer.Equals(Item2, other.Item2);
    }
    #endregion

    #region Optional - If you need to do string-based formatting
    public override string ToString() { return ToString(null, CultureInfo.CurrentCulture); }
    public string ToString(string format, IFormatProvider formatProvider)
    {
        return string.Format(formatProvider, format ?? "{0},{1}", Item1, Item2);
    }
    #endregion
}

Newmarket

Nice answer. This is what i was looking for (i'm on a project where i'm stuck at 3.5). Question : your GetHashCode() implementation is (h1 << 3) ^ h2 while MS one (trought ILSpy) is (h1 << 5) + h1 ^ h2. does it really make a difference (performance wise) ? – Chifley

@Chifley XOR should be ever so slightly faster in terms the amount of silicon that get used to do it (it's still one CPU instruction though). That is seriously overdoing micro-optimization though - feel free to use whichever you see fit. – Newmarket

I was thinking about possible collisions rather than time taken by to compute a hash code. – Chifley

@Chifley I guess the only way would be to test it. – Newmarket

This is quite good, avoids boxing (which even the .NET implementation doesn't do). A small suggestion, you dont need the null check in your hash code function, the comparer does it for you. – Wernick

Brilliant. 'nuff said. – Hypno

Answer 4

You can install NetLegacySupport.Tuple via nuget. This is the Tuple class from .Net 4.5 backported to .Net 2.0 and 3.5.

You can install this via the package manager in Visual Studio or using nuget on the commandline.

Here is the nuget package:

https://www.nuget.org/packages/NetLegacySupport.Tuple

Arthritis

Answer 5

Yes, there is a class called System.Collections.Generic.KeyValuePair that does the same thing (since .NET 2.0 I think).

http://msdn.microsoft.com/en-us/library/5tbh8a42.aspx

Rite

Yup, but that is not that useful if you want to return more than two values. Although you could nest KeyValuePairs within other KeyValuePairs for a quick fix. – Jackscrew

However, if what you have is not "a key and a value", it makes more sense to create your own custom structs or classes, or define some Tuple classes, like other answers. Poor practice to use a structure that implies you have "a key and a value", when you don't. Please avoid misleading people who have to read your code later! – Landry

Apologies for the downvote, as some people may consider this a useful work-around (though per my above comment, I consider this misleading), but more recent answers that give links to complete tuple implementations in mono and nuget should be higher than this answer. – Landry

Answer 6

Yes, you can just use Tuple.cs from mono:

You require the dependencies as well:
Tuples.cs
IStructuralComparable.cs
IStructuralEquatable.cs

You just put a

#define NET_4_0

in front of every

#if NET_4_0

and there you go, a feature-complete implementation of System.Tuple for .NET 2.0.

Exigent

Links provided are dead – Blameful

@Dav Evans: Updated. – Exigent