Tuples

In C#, a tuple is a data structure which organizes data, holding two or more fields of any type. A tuple is typically created by placing 2 or more expressions separated by commas, within a set of parentheses:

string boast = "All you need to know";
bool success = !string.IsNullOrWhiteSpace(boast);

// A tuple with three fields (triple)
(bool, int, string) triple = (success, 42, boast);

A tuple can be used in assignment and initialization operations, as a return value or a method argument. Fields are extracted using dot syntax. By default, the first field is Item1, the second Item2, etc. Non-default names are discussed below.

// initialization
(int, int, int) vertices = (90, 45, 45);

// assignment
vertices = (60, 60, 60);

//  return value
(bool, int) GetSameOrBigger(int num1, int num2)
{
    return (num1 == num2, num1 > num2 ? num1 : num2);
}

// method argument
int Add((int, int) operands)
{
    return operands.Item1 + operands.Item2;
}

Field names Item1 etc. do not make for readable code. The code below shows 2 ways to name the fields of tuples:

// name items in declaration
(bool success, string message) results = (true, "well done!");
bool mySuccess = results.success;
string myMessage = results.message;

// name items in creating expression
var results2 = (success: true, message: "well done!");
bool mySuccess2 = results2.success;
string myMessage2 = results2.message;

Use cases of tuples

One of the most common use cases of tuples is as a method return type. That is, instead of defining out method parameters, you can group method results in a tuple return type, as the following example shows:

(int min, int max) FindMinMax(int[] input)
{
    ...
}

var xs = new[] { 4, 7, 9 };
var limits = FindMinMax(xs);
Console.WriteLine($"Limits of [{string.Join(" ", xs)}] are {limits.min} and {limits.max}");

var ys = new[] { -9, 0, 67, 100 };
var (minimum, maximum) = FindMinMax(ys);
Console.WriteLine($"Limits of [{string.Join(" ", ys)}] are {minimum} and {maximum}");

• As the preceding example shows, you can work with the returned tuple instance directly or deconstruct it into separate variables.
• You can also use tuple types instead of anonymous types; for example, in LINQ queries. For more information, see Choosing between anonymous and tuple types.
• Typically, you use tuples to group loosely related data elements. In public APIs, consider defining a class or a structure type.