Boolean 結構

定義

代表布林值 (truefalse)。

public value class bool : IComparable, IComparable<bool>, IConvertible, IEquatable<bool>
public value class bool : IComparable, IConvertible
public value class bool : IComparable, IComparable<bool>, IEquatable<bool>
public struct Boolean : IComparable, IComparable<bool>, IConvertible, IEquatable<bool>
public readonly struct Boolean : IComparable, IComparable<bool>, IConvertible, IEquatable<bool>
[System.Serializable]
public struct Boolean : IComparable, IConvertible
[System.Serializable]
[System.Runtime.InteropServices.ComVisible(true)]
public struct Boolean : IComparable, IComparable<bool>, IConvertible, IEquatable<bool>
public struct Boolean : IComparable, IComparable<bool>, IEquatable<bool>
type bool = struct
    interface IConvertible
[<System.Serializable>]
type bool = struct
    interface IConvertible
[<System.Serializable>]
[<System.Runtime.InteropServices.ComVisible(true)>]
type bool = struct
    interface IConvertible
type bool = struct
Public Structure Boolean
Implements IComparable, IComparable(Of Boolean), IConvertible, IEquatable(Of Boolean)
Public Structure Boolean
Implements IComparable, IConvertible
Public Structure Boolean
Implements IComparable, IComparable(Of Boolean), IEquatable(Of Boolean)
繼承
Boolean
屬性
實作

備註

Boolean實例可以有兩個值之一: truefalse

結構 Boolean 提供支援下列工作的方法:

下列各節說明這些工作和其他使用詳細資料:

格式化布林值

Boolean 字串表示值為 「True」 true ,或值為 false 「False」。 值的字串表示 Boolean 是由唯讀 TrueStringFalseString 欄位所定義。

您可以使用 ToString 方法,將布林值轉換成字串。 布林結構包含兩 ToString 個多載:無 ToString() 參數方法和 ToString(IFormatProvider) 方法,其中包含控制格式設定的參數。 不過,因為忽略此參數,所以這兩個多載會產生相同的字串。 方法 ToString(IFormatProvider) 不支援區分文化特性的格式。

下列範例說明使用 ToString 方法的格式設定。 請注意,C# 和VB範例會使用複合格式設定功能,而 F# 範例則使用字串插補。 在這兩種情況下, ToString 都會隱含呼叫 方法。

using System;

public class Example
{
   public static void Main()
   {
      bool raining = false;
      bool busLate = true;

      Console.WriteLine("It is raining: {0}", raining);
      Console.WriteLine("The bus is late: {0}", busLate);
   }
}
// The example displays the following output:
//       It is raining: False
//       The bus is late: True
let raining = false
let busLate = true

printfn $"It is raining: {raining}"
printfn $"The bus is late: {busLate}"

// The example displays the following output:
//       It is raining: False
//       The bus is late: True
Module Example
   Public Sub Main()
      Dim raining As Boolean = False
      Dim busLate As Boolean = True

      Console.WriteLine("It is raining: {0}", raining)
      Console.WriteLine("The bus is late: {0}", busLate)
   End Sub
End Module
' The example displays the following output:
'       It is raining: False
'       The bus is late: True

Boolean因為 結構只能有兩個值,所以很容易加入自訂格式設定。 針對其他字串常值取代為 「True」 和 「False」 的簡單自訂格式,您可以使用語言支援的任何條件式評估功能,例如 C# 中的條件運算子或 Visual Basic 中的If 運算子。 下列範例會使用這項技術,將值格式化 Boolean 為 「Yes」 和 「No」,而不是 「True」 和 「False」。

using System;

public class Example
{
   public static void Main()
   {
      bool raining = false;
      bool busLate = true;

      Console.WriteLine("It is raining: {0}",
                        raining ? "Yes" : "No");
      Console.WriteLine("The bus is late: {0}",
                        busLate ? "Yes" : "No" );
   }
}
// The example displays the following output:
//       It is raining: No
//       The bus is late: Yes
Module Example
   Public Sub Main()
      Dim raining As Boolean = False
      Dim busLate As Boolean = True

      Console.WriteLine("It is raining: {0}", 
                        If(raining, "Yes", "No"))
      Console.WriteLine("The bus is late: {0}", 
                        If(busLate, "Yes", "No"))
   End Sub
End Module
' The example displays the following output:
'       It is raining: No
'       The bus is late: Yes
let raining = false
let busLate = true

printfn $"""It is raining: %s{if raining then "Yes" else "No"}"""
printfn $"""The bus is late: %s{if busLate then "Yes" else "No"}"""

// The example displays the following output:
//       It is raining: No
//       The bus is late: Yes

如需更複雜的自訂格式設定作業,包括區分文化特性的格式設定,您可以呼叫 String.Format(IFormatProvider, String, Object[]) 方法並提供實作 ICustomFormatter 。 下列範例會實作 ICustomFormatterIFormatProvider 介面,以提供區分文化特性的布林字串給英文 (美國) 、法文 (法國) ,以及俄文 (俄羅斯) 文化特性。

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      String[] cultureNames = { "", "en-US", "fr-FR", "ru-RU" };
      foreach (var cultureName in cultureNames) {
         bool value = true;
         CultureInfo culture = CultureInfo.CreateSpecificCulture(cultureName);
         BooleanFormatter formatter = new BooleanFormatter(culture);

         string result = string.Format(formatter, "Value for '{0}': {1}", culture.Name, value);
         Console.WriteLine(result);
      }
   }
}

public class BooleanFormatter : ICustomFormatter, IFormatProvider
{
   private CultureInfo culture;

   public BooleanFormatter() : this(CultureInfo.CurrentCulture)
   { }

   public BooleanFormatter(CultureInfo culture)
   {
      this.culture = culture;
   }

   public Object GetFormat(Type formatType)
   {
      if (formatType == typeof(ICustomFormatter))
         return this;
      else
         return null;
   }

   public string Format(string fmt, Object arg, IFormatProvider formatProvider)
   {
      // Exit if another format provider is used.
      if (! formatProvider.Equals(this)) return null;

      // Exit if the type to be formatted is not a Boolean
      if (! (arg is Boolean)) return null;

      bool value = (bool) arg;
      switch (culture.Name) {
         case "en-US":
            return value.ToString();
         case "fr-FR":
            if (value)
               return "vrai";
            else
               return "faux";
         case "ru-RU":
            if (value)
               return "верно";
            else
               return "неверно";
         default:
            return value.ToString();
      }
   }
}
// The example displays the following output:
//       Value for '': True
//       Value for 'en-US': True
//       Value for 'fr-FR': vrai
//       Value for 'ru-RU': верно
open System
open System.Globalization

type BooleanFormatter(culture) =
    interface ICustomFormatter with
        member this.Format(_, arg, formatProvider) =
            if formatProvider <> this then null
            else
                match arg with
                | :? bool as value -> 
                    match culture.Name with 
                    | "en-US" -> string arg
                    | "fr-FR" when value -> "vrai"
                    | "fr-FR" -> "faux"
                    | "ru-RU" when value -> "верно"
                    | "ru-RU" -> "неверно"
                    | _ -> string arg
                | _ -> null
    interface IFormatProvider with
        member this.GetFormat(formatType) =
            if formatType = typeof<ICustomFormatter> then this
            else null
    new() = BooleanFormatter CultureInfo.CurrentCulture

let cultureNames = [ ""; "en-US"; "fr-FR"; "ru-RU" ]
for cultureName in cultureNames do
    let value = true
    let culture = CultureInfo.CreateSpecificCulture cultureName 
    let formatter = BooleanFormatter culture

    String.Format(formatter, "Value for '{0}': {1}", culture.Name, value)
    |> printfn "%s"

// The example displays the following output:
//       Value for '': True
//       Value for 'en-US': True
//       Value for 'fr-FR': vrai
//       Value for 'ru-RU': верно
Imports System.Globalization

Module Example
   Public Sub Main()
      Dim cultureNames() As String = { "", "en-US", "fr-FR", "ru-RU" }
      For Each cultureName In cultureNames
         Dim value As Boolean = True
         Dim culture As CultureInfo = CultureInfo.CreateSpecificCulture(cultureName)
         Dim formatter As New BooleanFormatter(culture)
         
         Dim result As String = String.Format(formatter, "Value for '{0}': {1}", culture.Name, value)
         Console.WriteLine(result)
      Next
   End Sub
End Module

Public Class BooleanFormatter 
   Implements ICustomFormatter, IFormatProvider
   
   Private culture As CultureInfo
   
   Public Sub New()
      Me.New(CultureInfo.CurrentCulture)
   End Sub
   
   Public Sub New(culture As CultureInfo)
      Me.culture = culture 
   End Sub
   
   Public Function GetFormat(formatType As Type) As Object _
                   Implements IFormatProvider.GetFormat
      If formatType Is GetType(ICustomFormatter) Then
         Return Me
      Else
         Return Nothing
      End If                
   End Function
   
   Public Function Format(fmt As String, arg As Object, 
                          formatProvider As IFormatProvider) As String _
                   Implements ICustomFormatter.Format
      ' Exit if another format provider is used.
      If Not formatProvider.Equals(Me) Then Return Nothing
      
      ' Exit if the type to be formatted is not a Boolean
      If Not TypeOf arg Is Boolean Then Return Nothing
      
      Dim value As Boolean = CBool(arg)
      Select culture.Name
         Case "en-US"
            Return value.ToString()
         Case "fr-FR"
            If value Then
               Return "vrai"
            Else
               Return "faux"
            End If      
         Case "ru-RU"
            If value Then
               Return "верно"
            Else
               Return "неверно"
            End If   
         Case Else
            Return value.ToString()  
      End Select
   End Function
End Class
' The example displays the following output:
'          Value for '': True
'          Value for 'en-US': True
'          Value for 'fr-FR': vrai
'          Value for 'ru-RU': верно

您可以選擇性地使用 資源檔 來定義特定文化特性的布林字串。

轉換至布林值和從布林值

結構會 Boolean 實作 IConvertible 介面。 因此,您可以使用 Convert 類別來執行值與 .NET 中任何其他基本型別之間的 Boolean 轉換,或者您可以呼叫 Boolean 結構的明確實作。 不過,不支援 在 和下列類型之間進行 Boolean 轉換,因此對應的轉換方法會擲回 InvalidCastException 例外狀況:

從整數或浮點數到布林值的所有轉換,都會將非零值 true 轉換為 ,並將零值轉換成 false 。 下列範例會藉由呼叫 類別的選取多 Convert.ToBoolean 載來說明此問題。

using System;

public class Example
{
   public static void Main()
   {
      Byte byteValue = 12;
      Console.WriteLine(Convert.ToBoolean(byteValue));
      Byte byteValue2 = 0;
      Console.WriteLine(Convert.ToBoolean(byteValue2));
      int intValue = -16345;
      Console.WriteLine(Convert.ToBoolean(intValue));
      long longValue = 945;
      Console.WriteLine(Convert.ToBoolean(longValue));
      SByte sbyteValue = -12;
      Console.WriteLine(Convert.ToBoolean(sbyteValue));
      double dblValue = 0;
      Console.WriteLine(Convert.ToBoolean(dblValue));
      float sngValue = .0001f;
      Console.WriteLine(Convert.ToBoolean(sngValue));
   }
}
// The example displays the following output:
//       True
//       False
//       True
//       True
//       True
//       False
//       True
open System

let byteValue = 12uy
printfn $"{Convert.ToBoolean byteValue}"
let byteValue2 = 0uy
printfn $"{Convert.ToBoolean byteValue2}"
let intValue = -16345
printfn $"{Convert.ToBoolean intValue}"
let longValue = 945L
printfn $"{Convert.ToBoolean longValue}"
let sbyteValue = -12y
printfn $"{Convert.ToBoolean sbyteValue}"
let dblValue = 0.0
printfn $"{Convert.ToBoolean dblValue}"
let sngValue = 0.0001f
printfn $"{Convert.ToBoolean sngValue}"

// The example displays the following output:
//       True
//       False
//       True
//       True
//       True
//       False
//       True
Module Example
   Public Sub Main()
      Dim byteValue As Byte = 12
      Console.WriteLine(Convert.ToBoolean(byteValue))
      Dim byteValue2 As Byte = 0
      Console.WriteLine(Convert.ToBoolean(byteValue2))
      Dim intValue As Integer = -16345
      Console.WriteLine(Convert.ToBoolean(intValue))
      Dim longValue As Long = 945
      Console.WriteLine(Convert.ToBoolean(longValue))
      Dim sbyteValue As SByte = -12
      Console.WriteLine(Convert.ToBoolean(sbyteValue))
      Dim dblValue As Double = 0
      Console.WriteLine(Convert.ToBoolean(dblValue))
      Dim sngValue As Single = .0001
      Console.WriteLine(Convert.ToBoolean(sngValue))
   End Sub
End Module
' The example displays the following output:
'       True
'       False
'       True
'       True
'       True
'       False
'       True

從布林值轉換成數值時,類別的 Convert 轉換方法會轉換成 true 1 和 false 0。 不過,Visual Basic轉換函式會轉換成 255 (,以轉換成 true Byte 值) 或 -1 (,以用於所有其他數值轉換) 。 下列範例會 true 使用 Convert 方法轉換成數值,如果是Visual Basic範例,請使用Visual Basic語言自己的轉換運算子。

using System;

public class Example
{
   public static void Main()
   {
      bool flag = true;

      byte byteValue;
      byteValue = Convert.ToByte(flag);
      Console.WriteLine("{0} -> {1}", flag, byteValue);

      sbyte sbyteValue;
      sbyteValue = Convert.ToSByte(flag);
      Console.WriteLine("{0} -> {1}", flag, sbyteValue);

      double dblValue;
      dblValue = Convert.ToDouble(flag);
      Console.WriteLine("{0} -> {1}", flag, dblValue);

      int intValue;
      intValue = Convert.ToInt32(flag);
      Console.WriteLine("{0} -> {1}", flag, intValue);
   }
}
// The example displays the following output:
//       True -> 1
//       True -> 1
//       True -> 1
//       True -> 1
open System

let flag = true

let byteValue = Convert.ToByte flag
printfn $"{flag} -> {byteValue}"

let sbyteValue = Convert.ToSByte flag
printfn $"{flag} -> {sbyteValue}"

let dblValue = Convert.ToDouble flag
printfn $"{flag} -> {dblValue}"

let intValue = Convert.ToInt32(flag);
printfn $"{flag} -> {intValue}"

// The example displays the following output:
//       True -> 1
//       True -> 1
//       True -> 1
//       True -> 1
Module Example
   Public Sub Main()
      Dim flag As Boolean = true
      
      Dim byteValue As Byte   
      byteValue = Convert.ToByte(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, byteValue, 
                                            byteValue.GetType().Name)         
      byteValue = CByte(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, byteValue, 
                                            byteValue.GetType().Name)         
      
      Dim sbyteValue As SByte
      sbyteValue = Convert.ToSByte(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, sbyteValue, 
                                            sbyteValue.GetType().Name)         
      sbyteValue = CSByte(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, sbyteValue, 
                                            sbyteValue.GetType().Name)         

      Dim dblValue As Double
      dblValue = Convert.ToDouble(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, dblValue, 
                                            dblValue.GetType().Name)         
      dblValue = CDbl(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, dblValue, 
                                            dblValue.GetType().Name)         

      Dim intValue As Integer
      intValue = Convert.ToInt32(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, intValue, 
                                            intValue.GetType().Name)         
      intValue = CInt(flag)
      Console.WriteLine("{0} -> {1} ({2})", flag, intValue, 
                                            intValue.GetType().Name)         
   End Sub
End Module
' The example displays the following output:
'       True -> 1 (Byte)
'       True -> 255 (Byte)
'       True -> 1 (SByte)
'       True -> -1 (SByte)
'       True -> 1 (Double)
'       True -> -1 (Double)
'       True -> 1 (Int32)
'       True -> -1 (Int32)

如需從 Boolean 轉換成字串值的轉換,請參閱 格式化布林值 一節。 如需從字串轉換成 Boolean 值的轉換,請參閱 剖析布林值 一節。

剖析布林值

結構 Boolean 包含兩個靜態剖析方法, Parse 以及 TryParse ,可將字串轉換成布林值。 布林值的字串表示是由和 FalseString 欄位值的不區分大小寫對等值所定義,這些值 TrueString 分別為 「True」 和 「False」。 換句話說,剖析成功的唯一字串是 「True」、「False」、「true」、「false」 或某些混合大小寫的對等專案。 您無法成功剖析數值字串,例如 「0」 或 「1」。 執行字串比較時,不會考慮前置或尾端空白字元。

下列範例會使用 ParseTryParse 方法來剖析一些字串。 請注意,只能成功剖析不區分大小寫的 「True」 和 「False」。

using System;

public class Example
{
   public static void Main()
   {
      string[] values = { null, String.Empty, "True", "False",
                          "true", "false", "    true    ",
                           "TrUe", "fAlSe", "fa lse", "0",
                          "1", "-1", "string" };
      // Parse strings using the Boolean.Parse method.
      foreach (var value in values) {
         try {
            bool flag = Boolean.Parse(value);
            Console.WriteLine("'{0}' --> {1}", value, flag);
         }
         catch (ArgumentException) {
            Console.WriteLine("Cannot parse a null string.");
         }
         catch (FormatException) {
            Console.WriteLine("Cannot parse '{0}'.", value);
         }
      }
      Console.WriteLine();
      // Parse strings using the Boolean.TryParse method.
      foreach (var value in values) {
         bool flag = false;
         if (Boolean.TryParse(value, out flag))
            Console.WriteLine("'{0}' --> {1}", value, flag);
         else
            Console.WriteLine("Unable to parse '{0}'", value);
      }
   }
}
// The example displays the following output:
//       Cannot parse a null string.
//       Cannot parse ''.
//       'True' --> True
//       'False' --> False
//       'true' --> True
//       'false' --> False
//       '    true    ' --> True
//       'TrUe' --> True
//       'fAlSe' --> False
//       Cannot parse 'fa lse'.
//       Cannot parse '0'.
//       Cannot parse '1'.
//       Cannot parse '-1'.
//       Cannot parse 'string'.
//
//       Unable to parse ''
//       Unable to parse ''
//       'True' --> True
//       'False' --> False
//       'true' --> True
//       'false' --> False
//       '    true    ' --> True
//       'TrUe' --> True
//       'fAlSe' --> False
//       Cannot parse 'fa lse'.
//       Unable to parse '0'
//       Unable to parse '1'
//       Unable to parse '-1'
//       Unable to parse 'string'
open System

let values = 
    [ null; String.Empty; "True"; "False"
      "true"; "false"; "    true    "
      "TrUe"; "fAlSe"; "fa lse"; "0"
      "1"; "-1"; "string" ]
// Parse strings using the Boolean.Parse method.
for value in values do
    try
        let flag = Boolean.Parse value
        printfn $"'{value}' --> {flag}"
    with 
    | :? ArgumentException ->
        printfn "Cannot parse a null string."
    | :? FormatException ->
        printfn $"Cannot parse '{value}'."
printfn ""
// Parse strings using the Boolean.TryParse method.
for value in values do
    match Boolean.TryParse value with
    | true, flag -> 
        printfn $"'{value}' --> {flag}"
    | false, _ ->
        printfn $"Unable to parse '{value}'"

// The example displays the following output:
//       Cannot parse a null string.
//       Cannot parse ''.
//       'True' --> True
//       'False' --> False
//       'true' --> True
//       'false' --> False
//       '    true    ' --> True
//       'TrUe' --> True
//       'fAlSe' --> False
//       Cannot parse 'fa lse'.
//       Cannot parse '0'.
//       Cannot parse '1'.
//       Cannot parse '-1'.
//       Cannot parse 'string'.
//
//       Unable to parse ''
//       Unable to parse ''
//       'True' --> True
//       'False' --> False
//       'true' --> True
//       'false' --> False
//       '    true    ' --> True
//       'TrUe' --> True
//       'fAlSe' --> False
//       Cannot parse 'fa lse'.
//       Unable to parse '0'
//       Unable to parse '1'
//       Unable to parse '-1'
//       Unable to parse 'string'
Module Example
   Public Sub Main()
      Dim values() As String = { Nothing, String.Empty, "True", "False", 
                                 "true", "false", "    true    ", 
                                 "TrUe", "fAlSe", "fa lse", "0", 
                                 "1", "-1", "string" }
      ' Parse strings using the Boolean.Parse method.                    
      For Each value In values
         Try
            Dim flag As Boolean = Boolean.Parse(value)
            Console.WriteLine("'{0}' --> {1}", value, flag)
         Catch e As ArgumentException
            Console.WriteLine("Cannot parse a null string.")
         Catch e As FormatException
            Console.WriteLine("Cannot parse '{0}'.", value)
         End Try         
      Next  
      Console.WriteLine()
      ' Parse strings using the Boolean.TryParse method.                    
      For Each value In values
         Dim flag As Boolean = False
         If Boolean.TryParse(value, flag)
            Console.WriteLine("'{0}' --> {1}", value, flag)
         Else
            Console.WriteLine("Cannot parse '{0}'.", value)
         End If         
      Next  
   End Sub
End Module
' The example displays the following output:
'       Cannot parse a null string.
'       Cannot parse ''.
'       'True' --> True
'       'False' --> False
'       'true' --> True
'       'false' --> False
'       '    true    ' --> True
'       'TrUe' --> True
'       'fAlSe' --> False
'       Cannot parse 'fa lse'.
'       Cannot parse '0'.
'       Cannot parse '1'.
'       Cannot parse '-1'.
'       Cannot parse 'string'.
'       
'       Unable to parse ''
'       Unable to parse ''
'       'True' --> True
'       'False' --> False
'       'true' --> True
'       'false' --> False
'       '    true    ' --> True
'       'TrUe' --> True
'       'fAlSe' --> False
'       Cannot parse 'fa lse'.
'       Unable to parse '0'
'       Unable to parse '1'
'       Unable to parse '-1'
'       Unable to parse 'string'

如果您是在程式設計Visual Basic,您可以使用 函 CBool 式將數位的字串表示轉換成布林值。 「0」 會 false 轉換成 ,而任何非零值的字串表示會 true 轉換成 。 如果您不是在 Visual Basic 進行程式設計,您必須先將數值字串轉換成數位,才能將它轉換成布林值。 下列範例會藉由將整數陣列轉換成布林值來說明這一點。

using System;

public class Example
{
   public static void Main()
   {
      String[] values = { "09", "12.6", "0", "-13 " };
      foreach (var value in values) {
         bool success, result;
         int number;
         success = Int32.TryParse(value, out number);
         if (success) {
            // The method throws no exceptions.
            result = Convert.ToBoolean(number);
            Console.WriteLine("Converted '{0}' to {1}", value, result);
         }
         else {
            Console.WriteLine("Unable to convert '{0}'", value);
         }
      }
   }
}
// The example displays the following output:
//       Converted '09' to True
//       Unable to convert '12.6'
//       Converted '0' to False
//       Converted '-13 ' to True
open System

let values = [ "09"; "12.6"; "0"; "-13 " ]
for value in values do
    match Int32.TryParse value with
    | true, number -> 
        // The method throws no exceptions.
        let result = Convert.ToBoolean number
        printfn $"Converted '{value}' to {result}"
    | false, _ ->
        printfn $"Unable to convert '{value}'"

// The example displays the following output:
//       Converted '09' to True
//       Unable to convert '12.6'
//       Converted '0' to False
//       Converted '-13 ' to True
Module Example
   Public Sub Main()
      Dim values() As String = { "09", "12.6", "0", "-13 " }
      For Each value In values
         Dim success, result As Boolean
         Dim number As Integer 
         success = Int32.TryParse(value, number)
         If success Then
            ' The method throws no exceptions.
            result = Convert.ToBoolean(number)
            Console.WriteLine("Converted '{0}' to {1}", value, result)
         Else
            Console.WriteLine("Unable to convert '{0}'", value)
         End If         
      Next
   End Sub
End Module
' The example displays the following output:
'       Converted '09' to True
'       Unable to convert '12.6'
'       Converted '0' to False
'       Converted '-13 ' to True

比較布林值

由於布林值為 truefalse ,因此不需要明確呼叫 CompareTo 方法,這表示實例是否大於、小於或等於指定的值。 一般而言,若要比較兩個布林變數,您可以呼叫 Equals 方法或使用語言的相等運算子。

不過,當您想要比較布林變數與常值布林值 truefalse 時,不需要進行明確的比較,因為評估布林值的結果是布林值。 例如,運算式

if (booleanValue == true) {
if booleanValue = true then
If booleanValue = True Then

if (booleanValue) {
if booleanValue then
If booleanValue Then

相等,但第二個更精簡。 不過,這兩種技術都提供可比較的效能。

使用布林值做為二進位值

布林值會佔用一個位元組的記憶體,如下列 C# 或 F# 範例所示。 C# 範例必須使用 參數進行 /unsafe 編譯。

using System;

public struct BoolStruct
{
   public bool flag1;
   public bool flag2;
   public bool flag3;
   public bool flag4;
   public bool flag5;
}

public class Example
{
   public static void Main()
   {
      unsafe {
         BoolStruct b = new BoolStruct();
         bool* addr = (bool*) &b;
         Console.WriteLine("Size of BoolStruct: {0}", sizeof(BoolStruct));
         Console.WriteLine("Field offsets:");
         Console.WriteLine("   flag1: {0}", (bool*) &b.flag1 - addr);
         Console.WriteLine("   flag1: {0}", (bool*) &b.flag2 - addr);
         Console.WriteLine("   flag1: {0}", (bool*) &b.flag3 - addr);
         Console.WriteLine("   flag1: {0}", (bool*) &b.flag4 - addr);
         Console.WriteLine("   flag1: {0}", (bool*) &b.flag5 - addr);
      }
   }
}
// The example displays the following output:
//       Size of BoolStruct: 5
//       Field offsets:
//          flag1: 0
//          flag1: 1
//          flag1: 2
//          flag1: 3
//          flag1: 4
#nowarn "9" "51"
open FSharp.NativeInterop

[<Struct>]
type BoolStruct =
   val flag1: bool
   val flag2: bool
   val flag3: bool
   val flag4: bool
   val flag5: bool

let inline nint addr = NativePtr.toNativeInt addr

let mutable b = BoolStruct()
let addr = &&b

printfn $"Size of BoolStruct: {sizeof<BoolStruct>}"
printfn "Field offsets:"
printfn $"   flag1: {nint &&b.flag1 - nint addr}"
printfn $"   flag2: {nint &&b.flag2 - nint addr}"
printfn $"   flag3: {nint &&b.flag3 - nint addr}"
printfn $"   flag4: {nint &&b.flag4 - nint addr}"
printfn $"   flag5: {nint &&b.flag5 - nint addr}"

// The example displays the following output:
//       Size of BoolStruct: 5
//       Field offsets:
//          flag1: 0
//          flag1: 1
//          flag1: 2
//          flag1: 3
//          flag1: 4

位元組的低序位用來表示其值。 值為 1 表示 true ;值為 0 表示 false

提示

您可以使用 System.Collections.Specialized.BitVector32 結構來處理一組布林值。

您可以呼叫 BitConverter.GetBytes(Boolean) 方法,將布林值轉換成其二進位標記法。 方法會傳回具有單一元素的位元組陣列。 若要從其二進位標記法還原布林值,您可以呼叫 BitConverter.ToBoolean(Byte[], Int32) 方法。

下列範例會呼叫 BitConverter.GetBytes 方法,將布林值轉換成其二進位標記法,並顯示值的個別位,然後呼叫 BitConverter.ToBoolean 方法,以從其二進位標記法還原值。

using System;

public class Example
{
   public static void Main()
   {
      bool[] flags = { true, false };
      foreach (var flag in flags) {
         // Get binary representation of flag.
         Byte value = BitConverter.GetBytes(flag)[0];
         Console.WriteLine("Original value: {0}", flag);
         Console.WriteLine("Binary value:   {0} ({1})", value,
                           GetBinaryString(value));
         // Restore the flag from its binary representation.
         bool newFlag = BitConverter.ToBoolean( new Byte[] { value }, 0);
         Console.WriteLine("Restored value: {0}\n", flag);
      }
   }

   private static string GetBinaryString(Byte value)
   {
      string retVal = Convert.ToString(value, 2);
      return new string('0', 8 - retVal.Length) + retVal;
   }
}
// The example displays the following output:
//       Original value: True
//       Binary value:   1 (00000001)
//       Restored value: True
//
//       Original value: False
//       Binary value:   0 (00000000)
//       Restored value: False
open System

let getBinaryString (value: byte) =
   let retValue = Convert.ToString(value, 2)
   String('0', 8 - retValue.Length) + retValue

let flags = [ true; false ]
for flag in flags do
      // Get binary representation of flag.
      let value = BitConverter.GetBytes(flag)[0];
      printfn $"Original value: {flag}"
      printfn $"Binary value:   {value} ({getBinaryString value})"
      // Restore the flag from its binary representation.
      let newFlag = BitConverter.ToBoolean([|value|], 0)
      printfn $"Restored value: {newFlag}\n"

// The example displays the following output:
//       Original value: True
//       Binary value:   1 (00000001)
//       Restored value: True
//
//       Original value: False
//       Binary value:   0 (00000000)
//       Restored value: False
Module Example
   Public Sub Main()
      Dim flags() As Boolean = { True, False }
      For Each flag In flags
         ' Get binary representation of flag.
         Dim value As Byte = BitConverter.GetBytes(flag)(0)
         Console.WriteLine("Original value: {0}", flag)
         Console.WriteLine("Binary value:   {0} ({1})", value, 
                           GetBinaryString(value))
         ' Restore the flag from its binary representation.
         Dim newFlag As Boolean = BitConverter.ToBoolean( { value }, 0)
         Console.WriteLine("Restored value: {0}", flag)
         Console.WriteLine()
      Next
   End Sub
   
   Private Function GetBinaryString(value As Byte) As String
      Dim retVal As String = Convert.ToString(value, 2)
      Return New String("0"c, 8 - retVal.Length) + retVal
   End Function
End Module
' The example displays the following output:
'       Original value: True
'       Binary value:   1 (00000001)
'       Restored value: True
'       
'       Original value: False
'       Binary value:   0 (00000000)
'       Restored value: False

使用布林值執行作業

本節說明如何在應用程式中使用布林值。 第一節將討論其做為旗標的使用方式。 第二個說明其用於算數運算。

布林值做為旗標

布林值變數最常當做旗標使用,以發出某些條件是否存在的訊號。 例如,在 方法中 String.Compare(String, String, Boolean) ,final 參數 ignoreCase 是一個旗標,指出兩個字串的比較不區分大小寫 (ignoreCase true 是) 還是區分大小寫的 (ignoreCase false 是) 。 然後,您可以在條件陳述式中評估旗標的值。

下列範例會使用簡單的主控台應用程式來說明使用布林變數做為旗標。 應用程式會接受命令列參數,讓輸出重新導向至指定的檔案 (/f 參數) ,讓輸出同時傳送至指定的檔案和主控台 (參數) /b 。 應用程式會定義名為 isRedirected 的旗標,指出輸出是否要傳送至檔案,以及名為 isBoth 的旗標,指出輸出應該傳送至主控台。 請注意,F# 範例會使用 遞迴 函式來剖析引數。

using System;
using System.IO;
using System.Threading;

public class Example
{
   public static void Main()
   {
      // Initialize flag variables.
      bool isRedirected = false;
      bool isBoth = false;
      String fileName = "";
      StreamWriter sw = null;

      // Get any command line arguments.
      String[] args = Environment.GetCommandLineArgs();
      // Handle any arguments.
      if (args.Length > 1) {
         for (int ctr = 1; ctr < args.Length; ctr++) {
            String arg = args[ctr];
            if (arg.StartsWith("/") || arg.StartsWith("-")) {
               switch (arg.Substring(1).ToLower())
               {
                  case "f":
                     isRedirected = true;
                     if (args.Length < ctr + 2) {
                        ShowSyntax("The /f switch must be followed by a filename.");
                        return;
                     }
                     fileName = args[ctr + 1];
                     ctr++;
                     break;
                  case "b":
                     isBoth = true;
                     break;
                  default:
                     ShowSyntax(String.Format("The {0} switch is not supported",
                                              args[ctr]));
                     return;
               }
            }
         }
      }

      // If isBoth is True, isRedirected must be True.
      if (isBoth &&  ! isRedirected) {
         ShowSyntax("The /f switch must be used if /b is used.");
         return;
      }

      // Handle output.
      if (isRedirected) {
         sw = new StreamWriter(fileName);
         if (!isBoth)
            Console.SetOut(sw);
      }
      String msg = String.Format("Application began at {0}", DateTime.Now);
      Console.WriteLine(msg);
      if (isBoth) sw.WriteLine(msg);
      Thread.Sleep(5000);
      msg = String.Format("Application ended normally at {0}", DateTime.Now);
      Console.WriteLine(msg);
      if (isBoth) sw.WriteLine(msg);
      if (isRedirected) sw.Close();
   }

   private static void ShowSyntax(String errMsg)
   {
      Console.WriteLine(errMsg);
      Console.WriteLine("\nSyntax: Example [[/f <filename> [/b]]\n");
   }
}
open System
open System.IO
open System.Threading

let showSyntax errMsg =
    printfn $"{errMsg}\n\nSyntax: Example [[/f <filename> [/b]]\n" 

let mutable isRedirected = false
let mutable isBoth = false
let mutable fileName = ""

let rec parse = function
    | [] -> ()
    | "-b" :: rest
    | "/b" :: rest ->
        isBoth <- true
        // Parse remaining arguments.
        parse rest
    | "-f" :: file :: rest
    | "/f" :: file :: rest ->
        isRedirected <- true
        fileName <- file
        // Parse remaining arguments.
        parse rest
    | "-f" :: []
    | "/f" :: [] ->
        isRedirected <- true
        // No more arguments to parse.
    | x -> showSyntax $"The {x} switch is not supported"

Environment.GetCommandLineArgs()[1..]
|> List.ofArray
|> parse

// If isBoth is True, isRedirected must be True.
if isBoth && not isRedirected then
    showSyntax "The /f switch must be used if /b is used."
// If isRedirected is True, a fileName must be specified.
elif fileName = "" && isRedirected then
    showSyntax "The /f switch must be followed by a filename."    
else
    use mutable sw = null

    // Handle output.
    let writeLine =
        if isRedirected then 
            sw <- new StreamWriter(fileName)
            if isBoth then
                fun text -> 
                    printfn "%s" text
                    sw.WriteLine text
            else sw.WriteLine
        else printfn "%s"

    writeLine $"Application began at {DateTime.Now}"
    Thread.Sleep 5000
    writeLine $"Application ended normally at {DateTime.Now}"
Imports System.IO
Imports System.Threading

Module Example
   Public Sub Main()
      ' Initialize flag variables.
      Dim isRedirected, isBoth As Boolean 
      Dim fileName As String = ""
      Dim sw As StreamWriter = Nothing
      
      ' Get any command line arguments.
      Dim args() As String = Environment.GetCommandLineArgs()
      ' Handle any arguments.
      If args.Length > 1 Then
         For ctr = 1 To args.Length - 1
            Dim arg As String = args(ctr)
            If arg.StartsWith("/") OrElse arg.StartsWith("-") Then
               Select Case arg.Substring(1).ToLower()
                  Case "f"
                     isRedirected = True
                     If args.Length < ctr + 2 Then
                        ShowSyntax("The /f switch must be followed by a filename.")
                        Exit Sub
                     End If
                     fileName = args(ctr + 1)
                     ctr += 1
                  Case "b"
                     isBoth = True
                  Case Else
                     ShowSyntax(String.Format("The {0} switch is not supported", 
                                              args(ctr)))
                     Exit Sub
               End Select
            End If   
         Next
      End If

      ' If isBoth is True, isRedirected must be True.
      If isBoth And Not isRedirected Then 
         ShowSyntax("The /f switch must be used if /b is used.")
         Exit Sub
      End If

      ' Handle output.
      If isRedirected Then
         sw = New StreamWriter(fileName) 
         If Not IsBoth Then
            Console.SetOut(sw) 
         End If
      End If     
      Dim msg As String = String.Format("Application began at {0}", Date.Now)
      Console.WriteLine(msg)
      If isBoth Then sw.WriteLine(msg)
      Thread.Sleep(5000)
      msg = String.Format("Application ended normally at {0}", Date.Now)
      Console.WriteLine(msg)
      If isBoth Then sw.WriteLine(msg)
      If isRedirected Then sw.Close()
   End Sub
   
   Private Sub ShowSyntax(errMsg As String)
      Console.WriteLine(errMsg)
      Console.WriteLine()
      Console.WriteLine("Syntax: Example [[/f <filename> [/b]]")
      Console.WriteLine()
   End Sub
End Module

布林值和算數運算

布林值有時用來指出觸發數學計算的條件是否存在。 例如, hasShippingCharge 變數可能會做為旗標,以指出是否要將出貨費用新增至發票金額。

因為具有 false 值的作業不會影響運算的結果,所以不需要將布林值轉換成數學運算中使用的整數值。 相反地,您可以使用條件式邏輯。

下列範例會計算包含小計、出貨費用和選擇性服務費用的金額。 變數 hasServiceCharge 會決定是否套用服務費用。 範例會使用條件式邏輯來新增服務費用金額,而不是轉換成 hasServiceCharge 數值,並將它乘以服務費用金額。

using System;

public class Example
{
   public static void Main()
   {
      bool[] hasServiceCharges = { true, false };
      Decimal subtotal = 120.62m;
      Decimal shippingCharge = 2.50m;
      Decimal serviceCharge = 5.00m;

      foreach (var hasServiceCharge in hasServiceCharges) {
         Decimal total = subtotal + shippingCharge +
                                (hasServiceCharge ? serviceCharge : 0);
         Console.WriteLine("hasServiceCharge = {1}: The total is {0:C2}.",
                           total, hasServiceCharge);
      }
   }
}
// The example displays output like the following:
//       hasServiceCharge = True: The total is $128.12.
//       hasServiceCharge = False: The total is $123.12.
let hasServiceCharges = [ true; false ]
let subtotal = 120.62M
let shippingCharge = 2.50M
let serviceCharge = 5.00M

for hasServiceCharge in hasServiceCharges do
    let total = 
        subtotal + shippingCharge + if hasServiceCharge then serviceCharge else 0M
    printfn $"hasServiceCharge = {hasServiceCharge}: The total is {total:C2}."

// The example displays output like the following:
//       hasServiceCharge = True: The total is $128.12.
//       hasServiceCharge = False: The total is $123.12.
Module Example
   Public Sub Main()
      Dim hasServiceCharges() As Boolean = { True, False }
      Dim subtotal As Decimal = 120.62d
      Dim shippingCharge As Decimal = 2.50d
      Dim serviceCharge As Decimal = 5.00d
      
      For Each hasServiceCharge In hasServiceCharges
         Dim total As Decimal = subtotal + shippingCharge + 
                                If(hasServiceCharge, serviceCharge, 0)
         Console.WriteLine("hasServiceCharge = {1}: The total is {0:C2}.", 
                           total, hasServiceCharge)                       
      Next
   End Sub
End Module
' The example displays output like the following:
'       hasServiceCharge = True: The total is $128.12.
'       hasServiceCharge = False: The total is $123.12.

布林值和 Interop

雖然封送處理基底資料類型至 COM 通常很簡單,但 Boolean 資料類型是例外狀況。 您可以將 屬性套用 MarshalAsAttribute 至下列任一標記法封送 Boolean 處理類型:

列舉類型 Unmanaged 格式
UnmanagedType.Bool 4 位元組整數值,其中任何非零值都代表 true ,而 0 代表 false 。 這是結構中的欄位預設格式 Boolean ,以及 Boolean 平台叫用呼叫中的參數格式。
UnmanagedType.U1 1 位元組整數值,其中 1 代表 true ,而 0 代表 false
UnmanagedType.VariantBool 2 位元組整數值,其中 -1 代表 true ,而 0 代表 false 。 這是 COM Interop 呼叫中參數的預設格式 Boolean

欄位

FalseString

將布林值 false 表示為字串。 此欄位為唯讀。

TrueString

將布林值 true 表示為字串。 此欄位為唯讀。

方法

CompareTo(Boolean)

比較這個執行個體與指定的 Boolean 物件,並傳回整數,這個整數表示兩者彼此的關聯性。

CompareTo(Object)

將這個執行個體與指定的物件相比較,並傳回整數,這個整數表示兩者彼此的關聯性 (Relationship)。

Equals(Boolean)

傳回表示這個執行個體是否等於指定 Boolean 物件的值。

Equals(Object)

傳回值,該值表示這個執行個體是否和指定的物件相等。

GetHashCode()

傳回這個執行個體的雜湊碼。

GetTypeCode()

傳回 Boolean 實值類型的類型程式碼。

Parse(ReadOnlySpan<Char>)

將代表邏輯值的指定範圍轉換為其對等 Boolean

Parse(String)

將指定之邏輯值的字串表示,轉換為相等的 Boolean

ToString()

將這個執行個體的值轉換為它的對等字串表示 ("True" 或 "False")。

ToString(IFormatProvider)

將這個執行個體的值轉換為它的對等字串表示 ("True" 或 "False")。

TryFormat(Span<Char>, Int32)

嘗試將目前布林執行個體的值格式化為所提供字元範圍。

TryParse(ReadOnlySpan<Char>, Boolean)

嘗試將代表邏輯值的指定範圍轉換為對等 Boolean

TryParse(String, Boolean)

嘗試將指定之邏輯值的字串表示轉換成對等的 Boolean

明確介面實作

IComparable.CompareTo(Object)

將目前的執行個體與相同類型的另一個物件相比較,並傳回整數,這個整數表示目前的執行個體在排序次序中,位於另一個物件之前、之後或相同位置。

IConvertible.GetTypeCode()

傳回這個執行個體的 TypeCode

IConvertible.ToBoolean(IFormatProvider)

如需這個成員的說明,請參閱 ToBoolean(IFormatProvider)

IConvertible.ToByte(IFormatProvider)

如需這個成員的說明,請參閱 ToByte(IFormatProvider)

IConvertible.ToChar(IFormatProvider)

不支援此轉換。 嘗試使用這個方法會擲回 InvalidCastException

IConvertible.ToDateTime(IFormatProvider)

不支援此轉換。 嘗試使用這個方法會擲回 InvalidCastException

IConvertible.ToDecimal(IFormatProvider)

如需這個成員的說明,請參閱 ToDecimal(IFormatProvider)

IConvertible.ToDouble(IFormatProvider)

如需這個成員的說明,請參閱 ToDouble(IFormatProvider)

IConvertible.ToInt16(IFormatProvider)

如需這個成員的說明,請參閱 ToInt16(IFormatProvider)

IConvertible.ToInt32(IFormatProvider)

如需這個成員的說明,請參閱 ToInt32(IFormatProvider)

IConvertible.ToInt64(IFormatProvider)

如需這個成員的說明,請參閱 ToInt64(IFormatProvider)

IConvertible.ToSByte(IFormatProvider)

如需這個成員的說明,請參閱 ToSByte(IFormatProvider)

IConvertible.ToSingle(IFormatProvider)

如需這個成員的說明,請參閱 ToSingle(IFormatProvider)

IConvertible.ToString(IFormatProvider)

使用指定限定文化特性的格式資訊,將此執行個體的值轉換為相等字串。

IConvertible.ToType(Type, IFormatProvider)

如需這個成員的說明,請參閱 ToType(Type, IFormatProvider)

IConvertible.ToUInt16(IFormatProvider)

如需這個成員的說明,請參閱 ToUInt16(IFormatProvider)

IConvertible.ToUInt32(IFormatProvider)

如需這個成員的說明,請參閱 ToUInt32(IFormatProvider)

IConvertible.ToUInt64(IFormatProvider)

如需這個成員的說明,請參閱 ToUInt64(IFormatProvider)

適用於

執行緒安全性

此類型的所有成員都是安全線程。 看似修改實例狀態的成員,實際上會傳回以新值初始化的新實例。 如同任何其他類型,讀取和寫入包含此類型實例的共用變數必須受到鎖定保護,以確保執行緒安全。