Very often, in programming, you will need a data type that can only have one of two values, like:
- YES / NO
- ON / OFF
- TRUE / FALSE
For this, C# has a
bool data type, which can take the values
A boolean type is declared with the
bool keyword and can only take the values
bool isCSharpFun = true; bool isFishTasty = false; Console.WriteLine(isCSharpFun); // Outputs True Console.WriteLine(isFishTasty); // Outputs False
However, it is more common to return boolean values from boolean expressions, for conditional testing (see below).
A Boolean expression is a C# expression that returns a Boolean value:
You can use a comparison operator, such as the greater than (
>) operator to find out if an expression (or a variable) is true:
int x = 10; int y = 9; Console.WriteLine(x > y); // returns True, because 10 is higher than 9
Or even easier:
Console.WriteLine(10 > 9); // returns True, because 10 is higher than 9
In the examples below, we use the equal to (
==) operator to evaluate an expression:
int x = 10; Console.WriteLine(x == 10); // returns True, because the value of x is equal to 10
Console.WriteLine(10 == 15); // returns False, because 10 is not equal to 15
The boolean value of an expression is the basis for all C# comparisons and conditions.
You will learn more about conditions in the next chapter.