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C# Booleans


C#布尔值

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 true or false.


Boolean Values

A boolean type is declared with the bool keyword and can only take the values true or false:

Example

bool isCSharpFun = true;
bool isFishTasty = false;
Console.WriteLine(isCSharpFun);   // Outputs True
Console.WriteLine(isFishTasty);   // Outputs False

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However, it is more common to return boolean values from boolean expressions, for conditional testing (see below).


Boolean Expression

A Boolean expression is a C# expression that returns a Boolean value: True or False.

You can use a comparison operator, such as the greater than (>) operator to find out if an expression (or a variable) is true:

Example

int x = 10;
int y = 9;
Console.WriteLine(x > y); // returns True, because 10 is higher than 9

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Or even easier:

Example

Console.WriteLine(10 > 9); // returns True, because 10 is higher than 9

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In the examples below, we use the equal to (==) operator to evaluate an expression:

Example

int x = 10;
Console.WriteLine(x == 10); // returns True, because the value of x is equal to 10

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Example

Console.WriteLine(10 == 15); // returns False, because 10 is not equal to 15

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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.


C# 练习

Test Yourself With 练习

Exercise:

Fill in the missing parts to print the values True and False:

 isCodingFun = true;
 isFishTasty = false;
Console.WriteLine();
Console.WriteLine();

Start the Exercise





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