C# bool

bool 关键字是 System.Boolean 的别名。它用于声明变量来存储布尔值 true 和 false。

可将布尔值赋给 bool 变量。也可以将计算为 bool 类型的表达式赋给 bool 变量。

public class BoolTest
{
    static void Main()
    {
        bool b = true;

        // WriteLine automatically converts the value of b to text.
        Console.WriteLine(b);

        int days = DateTime.Now.DayOfYear;


        // Assign the result of a boolean expression to b.
        b = (days % 2 == 0);

        if (true == b)
        {
            Console.WriteLine("days is an even number");
        }
        else
        {
            Console.WriteLine("days is an odd number");
        }   
    }
}
/* Output:
  True
  days is an <even/odd> number
*/

 

若要测试 int
类型的变量，必须将该变量与一个值（例如零）进行显式比较，如下所示：

 

if (x != 0)   // The C# way
{
    Console.Write("The value of x is nonzero.");
}

在此例中，您从键盘输入一个字符，然后程序检查输入的字符是否是一个字母。如果字符是一个字母，则程序检查它是大写还是小写。这些检查是使用 IsLetter 和 IsLower（两者均返回 bool 类型）来执行的：

public class BoolKeyTest
{
    static void Main()
    {
        Console.Write("Enter a character: ");
        char c = (char)Console.Read();
        if (Char.IsLetter(c))
        {
            if (Char.IsLower(c))
            {
                Console.WriteLine("The character is lowercase.");
            }
            else
            {
                Console.WriteLine("The character is uppercase.");
            }
        }
        else
        {
            Console.WriteLine("Not an alphabetic character.");
        }
    }
}
/* Sample Output:
    Enter a character: X
    The character is uppercase.

    Enter a character: x
    The character is lowercase.

    Enter a character: 2
    The character is not an alphabetic character.
 */