DateTime addition

Leap
Leap in C# 
using System; // for DateTime

public static bool IsLeapYear(int year) => (new DateTime(year, 2, 28)).AddDays(1.0).Day == 29;

This approach may be considered a "cheat" for this exercise. By adding a day to February 28th for the year, you can see if the new day is the 29th or the 1st. If it is the 29th, then the year is a leap year. This is done by using the AddDays method and the Day property of the DateTime struct.

Shortening

When the body of a function is a single expression, the function can be implemented as an expression-bodied member, like so

public static bool IsLeapYear(int year) =>
  (new DateTime(year, 2, 28)).AddDays(1.0).Day == 29;

or

public static bool IsLeapYear(int year) => (new DateTime(year, 2, 28)).AddDays(1.0).Day == 29;
8th May 2024 · Found it useful?

Other Approaches to Leap in C#

Other ways our community solved this exercise
public static bool IsLeapYear(int year)
{
    return year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
}
Boolean chain

Use a chain of boolean expressions. 

public static bool IsLeapYear(int year)
{
    return year % 100 == 0 ? year % 400 == 0 : year % 4 == 0;
}
Ternary operator

Use a ternary operator of boolean expressions. 

return (year % 4, year % 100, year % 400) switch
{
    (_, 0, 0) => true,
    (_, 0, _) => false,
    (0, _, _) => true,
    _ => false,
};
switch on a tuple

Use a switch on a tuple made from boolean expressions. 

public static bool IsLeapYear(int year)
{
    return DateTime.IsLeapYear(year);
}
Built-in method

Use the built-in method.