# Boolean Struct

## Definition

Represents a Boolean (`true` or `false`) value.

``public value class Boolean : IComparable, IComparable<bool>, IConvertible, IEquatable<bool>``
``public value class Boolean : IComparable, IConvertible``
``public value class Boolean : IComparable, IComparable<bool>, IEquatable<bool>``
``public 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)``````
Inheritance
Boolean
Attributes
Implements

## Remarks

A Boolean instance can have either of two values: `true` or `false`.

The Boolean structure provides methods that support the following tasks:

The following sections explain these tasks and other usage details:

### Format Boolean values

The string representation of a Boolean is either "True" for a `true` value or "False" for a `false` value. The string representation of a Boolean value is defined by the read-only TrueString and FalseString fields.

You use the ToString method to convert Boolean values to strings. The Boolean structure includes two ToString overloads: the parameterless ToString() method and the ToString(IFormatProvider) method, which includes a parameter that controls formatting. However, because this parameter is ignored, the two overloads produce identical strings. The ToString(IFormatProvider) method does not support culture-sensitive formatting.

The following example illustrates formatting with the ToString method. Note that the example uses the composite formatting feature, so the ToString method is called implicitly.

``````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
``````
``````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
``````

Because the Boolean structure can have only two values, it is easy to add custom formatting. For simple custom formatting in which other string literals are substituted for "True" and "False", you can use any conditional evaluation feature supported by your language, such as the conditional operator in C# or the If operator in Visual Basic. The following example uses this technique to format Boolean values as "Yes" and "No" rather than "True" and "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
``````

For more complex custom formatting operations, including culture-sensitive formatting, you can call the String.Format(IFormatProvider, String, Object[]) method and provide an ICustomFormatter implementation. The following example implements the ICustomFormatter and IFormatProvider interfaces to provide culture-sensitive Boolean strings for the English (United States), French (France), and Russian (Russia) cultures.

``````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
``````
``````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
``````

Optionally, you can use resource files to define culture-specific Boolean strings.

### Convert to and from Boolean values

The Boolean structure implements the IConvertible interface. As a result, you can use the Convert class to perform conversions between a Boolean value and any other primitive type in .NET, or you can call the Boolean structure's explicit implementations. However, conversions between a Boolean and the following types are not supported, so the corresponding conversion methods throw an InvalidCastException exception:

All conversions from integral or floating-point numbers to Boolean values convert non-zero values to `true` and zero values to `false`. The following example illustrates this by calling selected overloads of the Convert.ToBoolean class.

``````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
``````
``````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
``````

When converting from Boolean to numeric values, the conversion methods of the Convert class convert `true` to 1 and `false` to 0. However, Visual Basic conversion functions convert `true` to either 255 (for conversions to Byte values) or -1 (for all other numeric conversions). The following example converts `true` to numeric values by using a Convert method, and, in the case of the Visual Basic example, by using the Visual Basic language's own conversion operator.

``````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
``````
``````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)
``````

For conversions from Boolean to string values, see the Formatting Boolean Values section. For conversions from strings to Boolean values, see the Parsing Boolean Values section.

### Parse Boolean values

The Boolean structure includes two static parsing methods, Parse and TryParse, that convert a string to a Boolean value. The string representation of a Boolean value is defined by the case-insensitive equivalents of the values of the TrueString and FalseString fields, which are "True" and "False", respectively. In other words, the only strings that parse successfully are "True", "False", "true", "false", or some mixed-case equivalent. You cannot successfully parse numeric strings such as "0" or "1". Leading or trailing white-space characters are not considered when performing the string comparison.

The following example uses the Parse and TryParse methods to parse a number of strings. Note that only the case-insensitive equivalents of "True" and "False" can be successfully parsed.

``````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'
``````
``````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'
``````

If you are programming in Visual Basic, you can use the `CBool` function to convert the string representation of a number to a Boolean value. "0" is converted to `false`, and the string representation of any non-zero value is converted to `true`. If you are not programming in Visual Basic, you must convert your numeric string to a number before converting it to a Boolean. The following example illustrates this by converting an array of integers to Boolean values.

``````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
``````
``````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
``````

### Compare Boolean values

Because Boolean values are either `true` or `false`, there is little reason to explicitly call the CompareTo method, which indicates whether an instance is greater than, less than, or equal to a specified value. Typically, to compare two Boolean variables, you call the Equals method or use your language's equality operator.

However, when you want to compare a Boolean variable with the literal Boolean value `true` or `false`, it is not necessary to do an explicit comparison, because the result of evaluating a Boolean value is that Boolean value. For example, the expressions

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

and

``````if (booleanValue) {
``````
``````If booleanValue Then
``````

are equivalent, but the second is more compact. However, both techniques offer comparable performance.

### Work with Booleans as binary values

A Boolean value occupies one byte of memory, as the following C# example shows. The example must be compiled with the `/unsafe` switch.

``````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
``````

The byte's low-order bit is used to represent its value. A value of 1 represents `true`; a value of 0 represents `false`.

Tip

You can use the System.Collections.Specialized.BitVector32 structure to work with sets of Boolean values.

You can convert a Boolean value to its binary representation by calling the BitConverter.GetBytes(Boolean) method. The method returns a byte array with a single element. To restore a Boolean value from its binary representation, you can call the BitConverter.ToBoolean(Byte[], Int32) method.

The following example calls the BitConverter.GetBytes method to convert a Boolean value to its binary representation and displays the individual bits of the value, and then calls the BitConverter.ToBoolean method to restore the value from its binary representation.

``````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);
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
``````
``````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
``````

### Perform operations with Boolean values

This section illustrates how Boolean values are used in apps. The first section discusses its use as a flag. The second illustrates its use for arithmetic operations.

#### Boolean values as flags

Boolean variables are most commonly used as flags, to signal the presence or absence of some condition. For example, in the String.Compare(String, String, Boolean) method, the final parameter, `ignoreCase`, is a flag that indicates whether the comparison of two strings is case-insensitive (`ignoreCase` is `true`) or case-sensitive (`ignoreCase` is `false`). The value of the flag can then be evaluated in a conditional statement.

The following example uses a simple console app to illustrate the use of Boolean variables as flags. The app accepts command-line parameters that enable output to be redirected to a specified file (the `/f` switch), and that enable output to be sent both to a specified file and to the console (the `/b` switch). The app defines a flag named `isRedirected` to indicate whether output is to be sent to a file, and a flag named `isBoth` to indicate that output should be sent to the console.

``````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");
}
}
``````
``````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
``````

#### Booleans and arithmetic operations

A Boolean value is sometimes used to indicate the presence of a condition that triggers a mathematical calculation. For example, a `hasShippingCharge` variable might serve as a flag to indicate whether to add shipping charges to an invoice amount.

Because an operation with a `false` value has no effect on the result of an operation, it is not necessary to convert the Boolean to an integral value to use in the mathematical operation. Instead, you can use conditional logic.

The following example computes an amount that consists of a subtotal, a shipping charge, and an optional service charge. The `hasServiceCharge` variable determines whether the service charge is applied. Instead of converting `hasServiceCharge` to a numeric value and multiplying it by the amount of the service charge, the example uses conditional logic to add the service charge amount if it is applicable.

``````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.
``````
``````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.
``````

#### Booleans and interop

While marshaling base data types to COM is generally straightforward, the Boolean data type is an exception. You can apply the MarshalAsAttribute attribute to marshal the Boolean type to any of the following representations:

Enumeration type Unmanaged format
UnmanagedType.Bool A 4-byte integer value, where any nonzero value represents `true` and 0 represents `false`. This is the default format of a Boolean field in a structure and of a Boolean parameter in platform invoke calls.
UnmanagedType.U1 A 1-byte integer value, where the 1 represents `true` and 0 represents `false`.
UnmanagedType.VariantBool A 2-byte integer value, where -1 represents `true` and 0 represents `false`. This is the default format of a Boolean parameter in COM interop calls.

## Fields

 Represents the Boolean value `false` as a string. This field is read-only. Represents the Boolean value `true` as a string. This field is read-only.

## Methods

 Compares this instance to a specified Boolean object and returns an integer that indicates their relationship to one another. Compares this instance to a specified object and returns an integer that indicates their relationship to one another. Returns a value indicating whether this instance is equal to a specified Boolean object. Returns a value indicating whether this instance is equal to a specified object. Returns the hash code for this instance. Returns the type code for the Boolean value type. Converts the specified span representation of a logical value to its Boolean equivalent. Converts the specified string representation of a logical value to its Boolean equivalent. Converts the value of this instance to its equivalent string representation (either "True" or "False"). Converts the value of this instance to its equivalent string representation (either "True" or "False"). Tries to format the value of the current boolean instance into the provided span of characters. Tries to convert the specified span representation of a logical value to its Boolean equivalent. Tries to convert the specified string representation of a logical value to its Boolean equivalent.

## Explicit Interface Implementations

 Compares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object. Returns the TypeCode for this instance. For a description of this member, see ToBoolean(IFormatProvider). For a description of this member, see ToByte(IFormatProvider). This conversion is not supported. Attempting to use this method throws an InvalidCastException. This conversion is not supported. Attempting to use this method throws an InvalidCastException. For a description of this member, see ToDecimal(IFormatProvider). For a description of this member, see ToDouble(IFormatProvider). For a description of this member, see ToInt16(IFormatProvider). For a description of this member, see ToInt32(IFormatProvider). For a description of this member, see ToInt64(IFormatProvider). For a description of this member, see ToSByte(IFormatProvider). For a description of this member, see ToSingle(IFormatProvider). Converts the value of this instance to an equivalent string using the specified culture-specific formatting information. For a description of this member, see ToType(Type, IFormatProvider). For a description of this member, see ToUInt16(IFormatProvider). For a description of this member, see ToUInt32(IFormatProvider). For a description of this member, see ToUInt64(IFormatProvider).

## Thread Safety

All members of this type are thread safe. Members that appear to modify instance state actually return a new instance initialized with the new value. As with any other type, reading and writing to a shared variable that contains an instance of this type must be protected by a lock to guarantee thread safety.
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