What is C# analog of C++ std::pair?


Question

I'm interested: What is C#'s analog of std::pair in C++? I found System.Web.UI.Pair class, but I'd prefer something template-based.

Thank you!

1
269
10/19/2018 11:17:28 AM

Accepted Answer

Tuples are available since .NET4.0 and support generics:

Tuple<string, int> t = new Tuple<string, int>("Hello", 4);

In previous versions you can use System.Collections.Generic.KeyValuePair<K, V> or a solution like the following:

public class Pair<T, U> {
    public Pair() {
    }

    public Pair(T first, U second) {
        this.First = first;
        this.Second = second;
    }

    public T First { get; set; }
    public U Second { get; set; }
};

And use it like this:

Pair<String, int> pair = new Pair<String, int>("test", 2);
Console.WriteLine(pair.First);
Console.WriteLine(pair.Second);

This outputs:

test
2

Or even this chained pairs:

Pair<Pair<String, int>, bool> pair = new Pair<Pair<String, int>, bool>();
pair.First = new Pair<String, int>();
pair.First.First = "test";
pair.First.Second = 12;
pair.Second = true;

Console.WriteLine(pair.First.First);
Console.WriteLine(pair.First.Second);
Console.WriteLine(pair.Second);

That outputs:

test
12
true
305
2/9/2017 9:43:09 PM

System.Web.UI contained the Pair class because it was used heavily in ASP.NET 1.1 as an internal ViewState structure.

Update Aug 2017: C# 7.0 / .NET Framework 4.7 provides a syntax to declare a Tuple with named items using the System.ValueTuple struct.

//explicit Item typing
(string Message, int SomeNumber) t = ("Hello", 4);
//or using implicit typing 
var t = (Message:"Hello", SomeNumber:4);

Console.WriteLine("{0} {1}", t.Message, t.SomeNumber);

see MSDN for more syntax examples.

Update Jun 2012: Tuples have been a part of .NET since version 4.0.

Here is an earlier article describing inclusion in.NET4.0 and support for generics:

Tuple<string, int> t = new Tuple<string, int>("Hello", 4);

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