Discard & Tuple

Discards (_)

Discards are placeholders that can be used to ignore the result of an expression or a method call. They are represented by an underscore character _ and can be used in place of a variable name when you don't need the value returned by an expression or a method call.

They are useful in situations where you need to call a method that returns a value, but you don't actually care about the value.

string[] dateStrings = {"05/01/2018 14:57:32.8", "2018-05-01 14:57:32.8", "2018-05-01T14:57:32.8375298-04:00", "5/01/2018",

"5/01/2018 14:57:32.80 -07:00", "1 May 2018 2:57:32.8 PM", "16-05-2018 1:00:32 PM", "Fri, 15 May 2018 20:10:57 GMT" };

foreach (string dateString in dateStrings)

{

if (DateTime.TryParse(dateString, out _))

Console.WriteLine($"'{dateString}': valid");

else

Console.WriteLine($"'{dateString}': invalid");

}

// The example displays output like the following:

// '05/01/2018 14:57:32.8': valid

// '2018-05-01 14:57:32.8': valid

// '2018-05-01T14:57:32.8375298-04:00': valid

// '5/01/2018': valid

// '5/01/2018 14:57:32.80 -07:00': valid

// '1 May 2018 2:57:32.8 PM': valid

// '16-05-2018 1:00:32 PM': invalid

// 'Fri, 15 May 2018 20:10:57 GMT': invalid

Tuple

A tuple is an object that contains a collection of related values, which can be of different data types. A tuple is similar to an array or a list, but it's designed to represent a fixed number of elements with specific types, rather than a variable number of elements.

var (_, _, _, pop1, _, pop2) = QueryCityDataForYears("New York City", 1960, 2010);

Console.WriteLine($"Population change, 1960 to 2010: {pop2 - pop1:N0}");

static (string, double, int, int, int, int) QueryCityDataForYears(string name, int year1, int year2)

{

int population1 = 0, population2 = 0;

double area = 0;

if (name == "New York City")

{

area = 468.48;

if (year1 == 1960) population1 = 7781984;

if (year2 == 2010) population2 = 8175133;

return (name, area, year1, population1, year2, population2);

}

return ("", 0, 0, 0, 0, 0);

}

// The example displays the following output:

// Population change, 1960 to 2010: 393,149

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