Overview: How to format numbers, dates, enums, and other types in .NET

Formatting is the process of converting an instance of a class or structure, or an enumeration value, to a string representation. The purpose is to display the resulting string to users or to deserialize it later to restore the original data type. This article introduces the formatting mechanisms that .NET provides.

Note

Parsing is the inverse of formatting. A parsing operation creates an instance of a data type from its string representation. For more information, see Parsing Strings. For information about serialization and deserialization, see Serialization in .NET.

The basic mechanism for formatting is the default implementation of the Object.ToString method, which is discussed in the Default Formatting Using the ToString Method section later in this topic. However, .NET provides several ways to modify and extend its default formatting support. These include the following:

• Overriding the Object.ToString method to define a custom string representation of an object's value. For more information, see the Override the ToString Method section later in this topic.

• Defining format specifiers that enable the string representation of an object's value to take multiple forms. For example, the "X" format specifier in the following statement converts an integer to the string representation of a hexadecimal value.

  int integerValue = 60312;
  Console.WriteLine(integerValue.ToString("X"));   // Displays EB98.
  

  Dim integerValue As Integer = 60312
  Console.WriteLine(integerValue.ToString("X"))   ' Displays EB98.
  

  For more information about format specifiers, see the ToString Method and Format Strings section.

• Using format providers to implement the formatting conventions of a specific culture. For example, the following statement displays a currency value by using the formatting conventions of the en-US culture.

  double cost = 1632.54;
  Console.WriteLine(cost.ToString("C",
                    new System.Globalization.CultureInfo("en-US")));
  // The example displays the following output:
  //       $1,632.54
  

  Dim cost As Double = 1632.54
  Console.WriteLine(cost.ToString("C", New System.Globalization.CultureInfo("en-US")))
  ' The example displays the following output:
  '       $1,632.54
  

  For more information about formatting with format providers, see the Format Providers section.

• Implementing the IFormattable interface to support both string conversion with the Convert class and composite formatting. For more information, see the IFormattable Interface section.

• Using composite formatting to embed the string representation of a value in a larger string. For more information, see the Composite Formatting section.

• Using string interpolation, a more readable syntax to embed the string representation of a value in a larger string. For more information, see String interpolation.

• Implementing ICustomFormatter and IFormatProvider to provide a complete custom formatting solution. For more information, see the Custom Formatting with ICustomFormatter section.

The following sections examine these methods for converting an object to its string representation.

Default formatting using the ToString method

Every type that is derived from System.Object automatically inherits a parameterless ToString method, which returns the name of the type by default. The following example illustrates the default ToString method. It defines a class named Automobile that has no implementation. When the class is instantiated and its ToString method is called, it displays its type name. Note that the ToString method is not explicitly called in the example. The Console.WriteLine(Object) method implicitly calls the ToString method of the object passed to it as an argument.

using System;

public class Automobile
{
   // No implementation. All members are inherited from Object.
}

public class Example9
{
   public static void Main()
   {
      Automobile firstAuto = new Automobile();
      Console.WriteLine(firstAuto);
   }
}
// The example displays the following output:
//       Automobile

Public Class Automobile
    ' No implementation. All members are inherited from Object.
End Class

Module Example9
    Public Sub Main9()
        Dim firstAuto As New Automobile()
        Console.WriteLine(firstAuto)
    End Sub
End Module
' The example displays the following output:
'       Automobile

Warning

Starting with Windows 8.1, the Windows Runtime includes an IStringable interface with a single method, IStringable.ToString, which provides default formatting support. However, we recommend that managed types do not implement the IStringable interface. For more information, see The Windows Runtime and the IStringable Interface.

Because all types other than interfaces are derived from Object, this functionality is automatically provided to your custom classes or structures. However, the functionality offered by the default ToString method, is limited: Although it identifies the type, it fails to provide any information about an instance of the type. To provide a string representation of an object that provides information about that object, you must override the ToString method.

Note

Structures inherit from ValueType, which in turn is derived from Object. Although ValueType overrides Object.ToString, its implementation is identical.

Override the ToString method

Displaying the name of a type is often of limited use and does not allow consumers of your types to differentiate one instance from another. However, you can override the ToString method to provide a more useful representation of an object's value. The following example defines a Temperature object and overrides its ToString method to display the temperature in degrees Celsius.

public class Temperature
{
    private decimal temp;

    public Temperature(decimal temperature)
    {
        this.temp = temperature;
    }

    public override string ToString()
    {
        return this.temp.ToString("N1") + "°C";
    }
}

public class Example12
{
    public static void Main()
    {
        Temperature currentTemperature = new Temperature(23.6m);
        Console.WriteLine($"The current temperature is {currentTemperature}");
    }
}
// The example displays the following output:
//       The current temperature is 23.6°C.

Public Class Temperature
    Private temp As Decimal

    Public Sub New(temperature As Decimal)
        Me.temp = temperature
    End Sub

    Public Overrides Function ToString() As String
        Return Me.temp.ToString("N1") + "°C"
    End Function
End Class

Module Example13
    Public Sub Main13()
        Dim currentTemperature As New Temperature(23.6D)
        Console.WriteLine("The current temperature is " +
                          currentTemperature.ToString())
    End Sub
End Module
' The example displays the following output:
'       The current temperature is 23.6°C.

In .NET, the ToString method of each primitive value type has been overridden to display the object's value instead of its name. The following table shows the override for each primitive type. Note that most of the overridden methods call another overload of the ToString method and pass it the "G" format specifier, which defines the general format for its type, and an IFormatProvider object that represents the current culture.

Type	ToString override
Boolean	Returns either Boolean.TrueString or Boolean.FalseString.
Byte	Calls Byte.ToString("G", NumberFormatInfo.CurrentInfo) to format the Byte value for the current culture.
Char	Returns the character as a string.
DateTime	Calls DateTime.ToString("G", DatetimeFormatInfo.CurrentInfo) to format the date and time value for the current culture.
Decimal	Calls Decimal.ToString("G", NumberFormatInfo.CurrentInfo) to format the Decimal value for the current culture.
Double	Calls Double.ToString("G", NumberFormatInfo.CurrentInfo) to format the Double value for the current culture.
Int16	Calls Int16.ToString("G", NumberFormatInfo.CurrentInfo) to format the Int16 value for the current culture.
Int32	Calls Int32.ToString("G", NumberFormatInfo.CurrentInfo) to format the Int32 value for the current culture.
Int64	Calls Int64.ToString("G", NumberFormatInfo.CurrentInfo) to format the Int64 value for the current culture.
SByte	Calls SByte.ToString("G", NumberFormatInfo.CurrentInfo) to format the SByte value for the current culture.
Single	Calls Single.ToString("G", NumberFormatInfo.CurrentInfo) to format the Single value for the current culture.
UInt16	Calls UInt16.ToString("G", NumberFormatInfo.CurrentInfo) to format the UInt16 value for the current culture.
UInt32	Calls UInt32.ToString("G", NumberFormatInfo.CurrentInfo) to format the UInt32 value for the current culture.
UInt64	Calls UInt64.ToString("G", NumberFormatInfo.CurrentInfo) to format the UInt64 value for the current culture.

The ToString method and format strings

Relying on the default ToString method or overriding ToString is appropriate when an object has a single string representation. However, the value of an object often has multiple representations. For example, a temperature can be expressed in degrees Fahrenheit, degrees Celsius, or kelvins. Similarly, the integer value 10 can be represented in numerous ways, including 10, 10.0, 1.0e01, or $10.00.

To enable a single value to have multiple string representations, .NET uses format strings. A format string is a string that contains one or more predefined format specifiers, which are single characters or groups of characters that define how the ToString method should format its output. The format string is then passed as a parameter to the object's ToString method and determines how the string representation of that object's value should appear.

All numeric types, date and time types, and enumeration types in .NET support a predefined set of format specifiers. You can also use format strings to define multiple string representations of your application-defined data types.

Standard format strings

A standard format string contains a single format specifier, which is an alphabetic character that defines the string representation of the object to which it is applied, along with an optional precision specifier that affects how many digits are displayed in the result string. If the precision specifier is omitted or is not supported, a standard format specifier is equivalent to a standard format string.

.NET defines a set of standard format specifiers for all numeric types, all date and time types, and all enumeration types. For example, each of these categories supports a "G" standard format specifier, which defines a general string representation of a value of that type.

Standard format strings for enumeration types directly control the string representation of a value. The format strings passed to an enumeration value's ToString method determine whether the value is displayed using its string name (the "G" and "F" format specifiers), its underlying integral value (the "D" format specifier), or its hexadecimal value (the "X" format specifier). The following example illustrates the use of standard format strings to format a DayOfWeek enumeration value.

DayOfWeek thisDay = DayOfWeek.Monday;
string[] formatStrings = {"G", "F", "D", "X"};

foreach (string formatString in formatStrings)
   Console.WriteLine(thisDay.ToString(formatString));
// The example displays the following output:
//       Monday
//       Monday
//       1
//       00000001

Dim thisDay As DayOfWeek = DayOfWeek.Monday
Dim formatStrings() As String = {"G", "F", "D", "X"}

For Each formatString As String In formatStrings
    Console.WriteLine(thisDay.ToString(formatString))
Next
' The example displays the following output:
'       Monday
'       Monday
'       1
'       00000001

For information about enumeration format strings, see Enumeration Format Strings.

Standard format strings for numeric types usually define a result string whose precise appearance is controlled by one or more property values. For example, the "C" format specifier formats a number as a currency value. When you call the ToString method with the "C" format specifier as the only parameter, the following property values from the current culture's NumberFormatInfo object are used to define the string representation of the numeric value:

• The CurrencySymbol property, which specifies the current culture's currency symbol.

• The CurrencyNegativePattern or CurrencyPositivePattern property, which returns an integer that determines the following:

  • The placement of the currency symbol.

  • Whether negative values are indicated by a leading negative sign, a trailing negative sign, or parentheses.

  • Whether a space appears between the numeric value and the currency symbol.

• The CurrencyDecimalDigits property, which defines the number of fractional digits in the result string.

• The CurrencyDecimalSeparator property, which defines the decimal separator symbol in the result string.

• The CurrencyGroupSeparator property, which defines the group separator symbol.

• The CurrencyGroupSizes property, which defines the number of digits in each group to the left of the decimal.

• The NegativeSign property, which determines the negative sign used in the result string if parentheses are not used to indicate negative values.

In addition, numeric format strings may include a precision specifier. The meaning of this specifier depends on the format string with which it is used, but it typically indicates either the total number of digits or the number of fractional digits that should appear in the result string. For example, the following example uses the "X4" standard numeric string and a precision specifier to create a string value that has four hexadecimal digits.

byte[] byteValues = { 12, 163, 255 };
foreach (byte byteValue in byteValues)
   Console.WriteLine(byteValue.ToString("X4"));
// The example displays the following output:
//       000C
//       00A3
//       00FF

Dim byteValues() As Byte = {12, 163, 255}
For Each byteValue As Byte In byteValues
    Console.WriteLine(byteValue.ToString("X4"))
Next
' The example displays the following output:
'       000C
'       00A3
'       00FF

For more information about standard numeric formatting strings, see Standard Numeric Format Strings.

Standard format strings for date and time values are aliases for custom format strings stored by a particular DateTimeFormatInfo property. For example, calling the ToString method of a date and time value with the "D" format specifier displays the date and time by using the custom format string stored in the current culture's DateTimeFormatInfo.LongDatePattern property. (For more information about custom format strings, see the next section.) The following example illustrates this relationship.

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      DateTime date1 = new DateTime(2009, 6, 30);
      Console.WriteLine("D Format Specifier:     {0:D}", date1);
      string longPattern = CultureInfo.CurrentCulture.DateTimeFormat.LongDatePattern;
      Console.WriteLine("'{0}' custom format string:     {1}",
                        longPattern, date1.ToString(longPattern));
   }
}
// The example displays the following output when run on a system whose
// current culture is en-US:
//    D Format Specifier:     Tuesday, June 30, 2009
//    'dddd, MMMM dd, yyyy' custom format string:     Tuesday, June 30, 2009

Imports System.Globalization

Module Example
    Public Sub Main0()
        Dim date1 As Date = #6/30/2009#
        Console.WriteLine("D Format Specifier:     {0:D}", date1)
        Dim longPattern As String = CultureInfo.CurrentCulture.DateTimeFormat.LongDatePattern
        Console.WriteLine("'{0}' custom format string:     {1}",
                          longPattern, date1.ToString(longPattern))
    End Sub
End Module
' The example displays the following output when run on a system whose
' current culture is en-US:
'    D Format Specifier:     Tuesday, June 30, 2009
'    'dddd, MMMM dd, yyyy' custom format string:     Tuesday, June 30, 2009

For more information about standard date and time format strings, see Standard Date and Time Format Strings.

You can also use standard format strings to define the string representation of an application-defined object that is produced by the object's ToString(String) method. You can define the specific standard format specifiers that your object supports, and you can determine whether they are case-sensitive or case-insensitive. Your implementation of the ToString(String) method should support the following:

• A "G" format specifier that represents a customary or common format of the object. The parameterless overload of your object's ToString method should call its ToString(String) overload and pass it the "G" standard format string.

• Support for a format specifier that is equal to a null reference (Nothing in Visual Basic). A format specifier that is equal to a null reference should be considered equivalent to the "G" format specifier.

For example, a Temperature class can internally store the temperature in degrees Celsius and use format specifiers to represent the value of the Temperature object in degrees Celsius, degrees Fahrenheit, and kelvins. The following example provides an illustration.

using System;

public class Temperature
{
   private decimal m_Temp;

   public Temperature(decimal temperature)
   {
      this.m_Temp = temperature;
   }

   public decimal Celsius
   {
      get { return this.m_Temp; }
   }

   public decimal Kelvin
   {
      get { return this.m_Temp + 273.15m; }
   }

   public decimal Fahrenheit
   {
      get { return Math.Round(((decimal) (this.m_Temp * 9 / 5 + 32)), 2); }
   }

   public override string ToString()
   {
      return this.ToString("C");
   }

   public string ToString(string format)
   {
      // Handle null or empty string.
      if (String.IsNullOrEmpty(format)) format = "C";
      // Remove spaces and convert to uppercase.
      format = format.Trim().ToUpperInvariant();

      // Convert temperature to Fahrenheit and return string.
      switch (format)
      {
         // Convert temperature to Fahrenheit and return string.
         case "F":
            return this.Fahrenheit.ToString("N2") + " °F";
         // Convert temperature to Kelvin and return string.
         case "K":
            return this.Kelvin.ToString("N2") + " K";
         // return temperature in Celsius.
         case "G":
         case "C":
            return this.Celsius.ToString("N2") + " °C";
         default:
            throw new FormatException(String.Format("The '{0}' format string is not supported.", format));
      }
   }
}

public class Example1
{
   public static void Main()
   {
      Temperature temp1 = new Temperature(0m);
      Console.WriteLine(temp1.ToString());
      Console.WriteLine(temp1.ToString("G"));
      Console.WriteLine(temp1.ToString("C"));
      Console.WriteLine(temp1.ToString("F"));
      Console.WriteLine(temp1.ToString("K"));

      Temperature temp2 = new Temperature(-40m);
      Console.WriteLine(temp2.ToString());
      Console.WriteLine(temp2.ToString("G"));
      Console.WriteLine(temp2.ToString("C"));
      Console.WriteLine(temp2.ToString("F"));
      Console.WriteLine(temp2.ToString("K"));

      Temperature temp3 = new Temperature(16m);
      Console.WriteLine(temp3.ToString());
      Console.WriteLine(temp3.ToString("G"));
      Console.WriteLine(temp3.ToString("C"));
      Console.WriteLine(temp3.ToString("F"));
      Console.WriteLine(temp3.ToString("K"));

      Console.WriteLine(String.Format("The temperature is now {0:F}.", temp3));
   }
}
// The example displays the following output:
//       0.00 °C
//       0.00 °C
//       0.00 °C
//       32.00 °F
//       273.15 K
//       -40.00 °C
//       -40.00 °C
//       -40.00 °C
//       -40.00 °F
//       233.15 K
//       16.00 °C
//       16.00 °C
//       16.00 °C
//       60.80 °F
//       289.15 K
//       The temperature is now 16.00 °C.

Public Class Temperature
    Private m_Temp As Decimal

    Public Sub New(temperature As Decimal)
        Me.m_Temp = temperature
    End Sub

    Public ReadOnly Property Celsius() As Decimal
        Get
            Return Me.m_Temp
        End Get
    End Property

    Public ReadOnly Property Kelvin() As Decimal
        Get
            Return Me.m_Temp + 273.15D
        End Get
    End Property

    Public ReadOnly Property Fahrenheit() As Decimal
        Get
            Return Math.Round(CDec(Me.m_Temp * 9 / 5 + 32), 2)
        End Get
    End Property

    Public Overrides Function ToString() As String
        Return Me.ToString("C")
    End Function

    Public Overloads Function ToString(format As String) As String
        ' Handle null or empty string.
        If String.IsNullOrEmpty(format) Then format = "C"
        ' Remove spaces and convert to uppercase.
        format = format.Trim().ToUpperInvariant()

        Select Case format
            Case "F"
                ' Convert temperature to Fahrenheit and return string.
                Return Me.Fahrenheit.ToString("N2") & " °F"
            Case "K"
                ' Convert temperature to Kelvin and return string.
                Return Me.Kelvin.ToString("N2") & " K"
            Case "C", "G"
                ' Return temperature in Celsius.
                Return Me.Celsius.ToString("N2") & " °C"
            Case Else
                Throw New FormatException(String.Format("The '{0}' format string is not supported.", format))
        End Select
    End Function
End Class

Public Module Example1
    Public Sub Main1()
        Dim temp1 As New Temperature(0D)
        Console.WriteLine(temp1.ToString())
        Console.WriteLine(temp1.ToString("G"))
        Console.WriteLine(temp1.ToString("C"))
        Console.WriteLine(temp1.ToString("F"))
        Console.WriteLine(temp1.ToString("K"))

        Dim temp2 As New Temperature(-40D)
        Console.WriteLine(temp2.ToString())
        Console.WriteLine(temp2.ToString("G"))
        Console.WriteLine(temp2.ToString("C"))
        Console.WriteLine(temp2.ToString("F"))
        Console.WriteLine(temp2.ToString("K"))

        Dim temp3 As New Temperature(16D)
        Console.WriteLine(temp3.ToString())
        Console.WriteLine(temp3.ToString("G"))
        Console.WriteLine(temp3.ToString("C"))
        Console.WriteLine(temp3.ToString("F"))
        Console.WriteLine(temp3.ToString("K"))

        Console.WriteLine(String.Format("The temperature is now {0:F}.", temp3))
    End Sub
End Module
' The example displays the following output:
'       0.00 °C
'       0.00 °C
'       0.00 °C
'       32.00 °F
'       273.15 K
'       -40.00 °C
'       -40.00 °C
'       -40.00 °C
'       -40.00 °F
'       233.15 K
'       16.00 °C
'       16.00 °C
'       16.00 °C
'       60.80 °F
'       289.15 K
'       The temperature is now 16.00 °C.

Custom format strings

In addition to the standard format strings, .NET defines custom format strings for both numeric values and date and time values. A custom format string consists of one or more custom format specifiers that define the string representation of a value. For example, the custom date and time format string "yyyy/mm/dd hh:mm:ss.ffff t zzz" converts a date to its string representation in the form "2008/11/15 07:45:00.0000 P -08:00" for the en-US culture. Similarly, the custom format string "0000" converts the integer value 12 to "0012". For a complete list of custom format strings, see Custom Date and Time Format Strings and Custom Numeric Format Strings.

If a format string consists of a single custom format specifier, the format specifier should be preceded by the percent (%) symbol to avoid confusion with a standard format specifier. The following example uses the "M" custom format specifier to display a one-digit or two-digit number of the month of a particular date.

DateTime date1 = new DateTime(2009, 9, 8);
Console.WriteLine(date1.ToString("%M"));       // Displays 9

Dim date1 As Date = #09/08/2009#
Console.WriteLine(date1.ToString("%M"))      ' Displays 9

Many standard format strings for date and time values are aliases for custom format strings that are defined by properties of the DateTimeFormatInfo object. Custom format strings also offer considerable flexibility in providing application-defined formatting for numeric values or date and time values. You can define your own custom result strings for both numeric values and date and time values by combining multiple custom format specifiers into a single custom format string. The following example defines a custom format string that displays the day of the week in parentheses after the month name, day, and year.

string customFormat = "MMMM dd, yyyy (dddd)";
DateTime date1 = new DateTime(2009, 8, 28);
Console.WriteLine(date1.ToString(customFormat));
// The example displays the following output if run on a system
// whose language is English:
//       August 28, 2009 (Friday)

Dim customFormat As String = "MMMM dd, yyyy (dddd)"
Dim date1 As Date = #8/28/2009#
Console.WriteLine(date1.ToString(customFormat))
' The example displays the following output if run on a system
' whose language is English:
'       August 28, 2009 (Friday)      

The following example defines a custom format string that displays an Int64 value as a standard, seven-digit U.S. telephone number along with its area code.

using System;

public class Example17
{
   public static void Main()
   {
      long number = 8009999999;
      string fmt = "000-000-0000";
      Console.WriteLine(number.ToString(fmt));
   }
}
// The example displays the following output:
//        800-999-9999

Module Example18
    Public Sub Main18()
        Dim number As Long = 8009999999
        Dim fmt As String = "000-000-0000"
        Console.WriteLine(number.ToString(fmt))
    End Sub
End Module
' The example displays the following output:

' The example displays the following output:
'       800-999-9999

Although standard format strings can generally handle most of the formatting needs for your application-defined types, you may also define custom format specifiers to format your types.

Format strings and .NET types

All numeric types (that is, the Byte, Decimal, Double, Int16, Int32, Int64, SByte, Single, UInt16, UInt32, UInt64, and BigInteger types), as well as the DateTime, DateTimeOffset, TimeSpan, Guid, and all enumeration types, support formatting with format strings. For information on the specific format strings supported by each type, see the following topics:

Title	Definition
Standard Numeric Format Strings	Describes standard format strings that create commonly used string representations of numeric values.
Custom Numeric Format Strings	Describes custom format strings that create application-specific formats for numeric values.
Standard Date and Time Format Strings	Describes standard format strings that create commonly used string representations of DateTime and DateTimeOffset values.
Custom Date and Time Format Strings	Describes custom format strings that create application-specific formats for DateTime and DateTimeOffset values.
Standard TimeSpan Format Strings	Describes standard format strings that create commonly used string representations of time intervals.
Custom TimeSpan Format Strings	Describes custom format strings that create application-specific formats for time intervals.
Enumeration Format Strings	Describes standard format strings that are used to create string representations of enumeration values.
Guid.ToString(String)	Describes standard format strings for Guid values.

Culture-sensitive formatting with format providers

Although format specifiers let you customize the formatting of objects, producing a meaningful string representation of objects often requires additional formatting information. For example, formatting a number as a currency value by using either the "C" standard format string or a custom format string such as "$ #,#.00" requires, at a minimum, information about the correct currency symbol, group separator, and decimal separator to be available to include in the formatted string. In .NET, this additional formatting information is made available through the IFormatProvider interface, which is provided as a parameter to one or more overloads of the ToString method of numeric types and date and time types. IFormatProvider implementations are used in .NET to support culture-specific formatting. The following example illustrates how the string representation of an object changes when it is formatted with three IFormatProvider objects that represent different cultures.

using System;
using System.Globalization;

public class Example18
{
   public static void Main()
   {
      decimal value = 1603.42m;
      Console.WriteLine(value.ToString("C3", new CultureInfo("en-US")));
      Console.WriteLine(value.ToString("C3", new CultureInfo("fr-FR")));
      Console.WriteLine(value.ToString("C3", new CultureInfo("de-DE")));
   }
}
// The example displays the following output:
//       $1,603.420
//       1 603,420 €
//       1.603,420 €

Imports System.Globalization

Public Module Example11
    Public Sub Main11()
        Dim value As Decimal = 1603.42D
        Console.WriteLine(value.ToString("C3", New CultureInfo("en-US")))
        Console.WriteLine(value.ToString("C3", New CultureInfo("fr-FR")))
        Console.WriteLine(value.ToString("C3", New CultureInfo("de-DE")))
    End Sub
End Module
' The example displays the following output:
'       $1,603.420
'       1 603,420 €
'       1.603,420 €

The IFormatProvider interface includes one method, GetFormat(Type), which has a single parameter that specifies the type of object that provides formatting information. If the method can provide an object of that type, it returns it. Otherwise, it returns a null reference (Nothing in Visual Basic).

IFormatProvider.GetFormat is a callback method. When you call a ToString method overload that includes an IFormatProvider parameter, it calls the GetFormat method of that IFormatProvider object. The GetFormat method is responsible for returning an object that provides the necessary formatting information, as specified by its formatType parameter, to the ToString method.

A number of formatting or string conversion methods include a parameter of type IFormatProvider, but in many cases the value of the parameter is ignored when the method is called. The following table lists some of the formatting methods that use the parameter and the type of the Type object that they pass to the IFormatProvider.GetFormat method.

Method	Type of formatType parameter
ToString method of numeric types	System.Globalization.NumberFormatInfo
ToString method of date and time types	System.Globalization.DateTimeFormatInfo
String.Format	System.ICustomFormatter
StringBuilder.AppendFormat	System.ICustomFormatter

Note

The ToString methods of the numeric types and date and time types are overloaded, and only some of the overloads include an IFormatProvider parameter. If a method does not have a parameter of type IFormatProvider, the object that is returned by the CultureInfo.CurrentCulture property is passed instead. For example, a call to the default Int32.ToString() method ultimately results in a method call such as the following: Int32.ToString("G", System.Globalization.CultureInfo.CurrentCulture).

.NET provides three classes that implement IFormatProvider:

• DateTimeFormatInfo, a class that provides formatting information for date and time values for a specific culture. Its IFormatProvider.GetFormat implementation returns an instance of itself.

• NumberFormatInfo, a class that provides numeric formatting information for a specific culture. Its IFormatProvider.GetFormat implementation returns an instance of itself.

• CultureInfo. Its IFormatProvider.GetFormat implementation can return either a NumberFormatInfo object to provide numeric formatting information or a DateTimeFormatInfo object to provide formatting information for date and time values.

You can also implement your own format provider to replace any one of these classes. However, your implementation's GetFormat method must return an object of the type listed in the previous table if it has to provide formatting information to the ToString method.

Culture-sensitive formatting of numeric values

By default, the formatting of numeric values is culture-sensitive. If you do not specify a culture when you call a formatting method, the formatting conventions of the current culture are used. This is illustrated in the following example, which changes the current culture four times and then calls the Decimal.ToString(String) method. In each case, the result string reflects the formatting conventions of the current culture. This is because the ToString and ToString(String) methods wrap calls to each numeric type's ToString(String, IFormatProvider) method.

using System.Globalization;

public class Example6
{
   public static void Main()
   {
      string[] cultureNames = { "en-US", "fr-FR", "es-MX", "de-DE" };
      Decimal value = 1043.17m;

      foreach (var cultureName in cultureNames) {
         // Change the current culture.
         CultureInfo.CurrentCulture = CultureInfo.CreateSpecificCulture(cultureName);
         Console.WriteLine($"The current culture is {CultureInfo.CurrentCulture.Name}");
         Console.WriteLine(value.ToString("C2"));
         Console.WriteLine();
      }
   }
}
// The example displays the following output:
//       The current culture is en-US
//       $1,043.17
//
//       The current culture is fr-FR
//       1 043,17 €
//
//       The current culture is es-MX
//       $1,043.17
//
//       The current culture is de-DE
//       1.043,17 €

Imports System.Globalization

Module Example6
    Public Sub Main6()
        Dim cultureNames() As String = {"en-US", "fr-FR", "es-MX", "de-DE"}
        Dim value As Decimal = 1043.17D

        For Each cultureName In cultureNames
            ' Change the current culture.
            CultureInfo.CurrentCulture = CultureInfo.CreateSpecificCulture(cultureName)
            Console.WriteLine($"The current culture is {CultureInfo.CurrentCulture.Name}")
            Console.WriteLine(value.ToString("C2"))
            Console.WriteLine()
        Next
    End Sub
End Module
' The example displays the following output:
'       The current culture is en-US
'       $1,043.17
'       
'       The current culture is fr-FR
'       1 043,17 €
'       
'       The current culture is es-MX
'       $1,043.17
'       
'       The current culture is de-DE
'       1.043,17 €

You can also format a numeric value for a specific culture by calling a ToString overload that has a provider parameter and passing it either of the following:

• A CultureInfo object that represents the culture whose formatting conventions are to be used. Its CultureInfo.GetFormat method returns the value of the CultureInfo.NumberFormat property, which is the NumberFormatInfo object that provides culture-specific formatting information for numeric values.

• A NumberFormatInfo object that defines the culture-specific formatting conventions to be used. Its GetFormat method returns an instance of itself.

The following example uses NumberFormatInfo objects that represent the English (United States) and English (United Kingdom) cultures and the French and Russian neutral cultures to format a floating-point number.

using System.Globalization;

public class Example7
{
    public static void Main()
    {
        double value = 1043.62957;
        string[] cultureNames = { "en-US", "en-GB", "ru", "fr" };

        foreach (string? name in cultureNames)
        {
            NumberFormatInfo nfi = CultureInfo.CreateSpecificCulture(name).NumberFormat;
            Console.WriteLine("{0,-6} {1}", name + ":", value.ToString("N3", nfi));
        }
    }
}
// The example displays the following output:
//       en-US: 1,043.630
//       en-GB: 1,043.630
//       ru:    1 043,630
//       fr:    1 043,630

Imports System.Globalization

Module Example7
    Public Sub Main7()
        Dim value As Double = 1043.62957
        Dim cultureNames() As String = {"en-US", "en-GB", "ru", "fr"}

        For Each name In cultureNames
            Dim nfi As NumberFormatInfo = CultureInfo.CreateSpecificCulture(name).NumberFormat
            Console.WriteLine("{0,-6} {1}", name + ":", value.ToString("N3", nfi))
        Next
    End Sub
End Module
' The example displays the following output:
'       en-US: 1,043.630
'       en-GB: 1,043.630
'       ru:    1 043,630
'       fr:    1 043,630

Culture-sensitive formatting of date and time values

By default, the formatting of date and time values is culture-sensitive. If you do not specify a culture when you call a formatting method, the formatting conventions of the current culture are used. This is illustrated in the following example, which changes the current culture four times and then calls the DateTime.ToString(String) method. In each case, the result string reflects the formatting conventions of the current culture. This is because the DateTime.ToString(), DateTime.ToString(String), DateTimeOffset.ToString(), and DateTimeOffset.ToString(String) methods wrap calls to the DateTime.ToString(String, IFormatProvider) and DateTimeOffset.ToString(String, IFormatProvider) methods.

using System.Globalization;

public class Example4
{
   public static void Main()
   {
      string[] cultureNames = { "en-US", "fr-FR", "es-MX", "de-DE" };
      DateTime dateToFormat = new DateTime(2012, 5, 28, 11, 30, 0);

      foreach (var cultureName in cultureNames) {
         // Change the current culture.
         CultureInfo.CurrentCulture = CultureInfo.CreateSpecificCulture(cultureName);
         Console.WriteLine($"The current culture is {CultureInfo.CurrentCulture.Name}");
         Console.WriteLine(dateToFormat.ToString("F"));
         Console.WriteLine();
      }
   }
}
// The example displays the following output:
//       The current culture is en-US
//       Monday, May 28, 2012 11:30:00 AM
//
//       The current culture is fr-FR
//       lundi 28 mai 2012 11:30:00
//
//       The current culture is es-MX
//       lunes, 28 de mayo de 2012 11:30:00 a.m.
//
//       The current culture is de-DE
//       Montag, 28. Mai 2012 11:30:00

Imports System.Globalization
Imports System.Threading

Module Example4
    Public Sub Main4()
        Dim cultureNames() As String = {"en-US", "fr-FR", "es-MX", "de-DE"}
        Dim dateToFormat As Date = #5/28/2012 11:30AM#

        For Each cultureName In cultureNames
            ' Change the current culture.
            CultureInfo.CurrentCulture = CultureInfo.CreateSpecificCulture(cultureName)
            Console.WriteLine($"The current culture is {CultureInfo.CurrentCulture.Name}")
            Console.WriteLine(dateToFormat.ToString("F"))
            Console.WriteLine()
        Next
    End Sub
End Module
' The example displays the following output:
'       The current culture is en-US
'       Monday, May 28, 2012 11:30:00 AM
'       
'       The current culture is fr-FR
'       lundi 28 mai 2012 11:30:00
'       
'       The current culture is es-MX
'       lunes, 28 de mayo de 2012 11:30:00 a.m.
'       
'       The current culture is de-DE
'       Montag, 28. Mai 2012 11:30:00 

You can also format a date and time value for a specific culture by calling a DateTime.ToString or DateTimeOffset.ToString overload that has a provider parameter and passing it either of the following:

• A CultureInfo object that represents the culture whose formatting conventions are to be used. Its CultureInfo.GetFormat method returns the value of the CultureInfo.DateTimeFormat property, which is the DateTimeFormatInfo object that provides culture-specific formatting information for date and time values.

• A DateTimeFormatInfo object that defines the culture-specific formatting conventions to be used. Its GetFormat method returns an instance of itself.

The following example uses DateTimeFormatInfo objects that represent the English (United States) and English (United Kingdom) cultures and the French and Russian neutral cultures to format a date.

using System.Globalization;

public class Example5
{
   public static void Main()
   {
      DateTime dat1 = new(2012, 5, 28, 11, 30, 0);
      string[] cultureNames = { "en-US", "en-GB", "ru", "fr" };

      foreach (var name in cultureNames) {
         DateTimeFormatInfo dtfi = CultureInfo.CreateSpecificCulture(name).DateTimeFormat;
         Console.WriteLine($"{name}: {dat1.ToString(dtfi)}");
      }
   }
}
// The example displays the following output:
//       en-US: 5/28/2012 11:30:00 AM
//       en-GB: 28/05/2012 11:30:00
//       ru: 28.05.2012 11:30:00
//       fr: 28/05/2012 11:30:00

Imports System.Globalization

Module Example5
    Public Sub Main5()
        Dim dat1 As Date = #5/28/2012 11:30AM#
        Dim cultureNames() As String = {"en-US", "en-GB", "ru", "fr"}

        For Each name In cultureNames
            Dim dtfi As DateTimeFormatInfo = CultureInfo.CreateSpecificCulture(name).DateTimeFormat
            Console.WriteLine($"{name}: {dat1.ToString(dtfi)}")
        Next
    End Sub
End Module
' The example displays the following output:
'       en-US: 5/28/2012 11:30:00 AM
'       en-GB: 28/05/2012 11:30:00
'       ru: 28.05.2012 11:30:00
'       fr: 28/05/2012 11:30:00

The IFormattable interface

Typically, types that overload the ToString method with a format string and an IFormatProvider parameter also implement the IFormattable interface. This interface has a single member, IFormattable.ToString(String, IFormatProvider), that includes both a format string and a format provider as parameters.

Implementing the IFormattable interface for your application-defined class offers two advantages:

• Support for string conversion by the Convert class. Calls to the Convert.ToString(Object) and Convert.ToString(Object, IFormatProvider) methods call your IFormattable implementation automatically.

• Support for composite formatting. If a format item that includes a format string is used to format your custom type, the common language runtime automatically calls your IFormattable implementation and passes it the format string. For more information about composite formatting with methods such as String.Format or Console.WriteLine, see the Composite Formatting section.

The following example defines a Temperature class that implements the IFormattable interface. It supports the "C" or "G" format specifiers to display the temperature in Celsius, the "F" format specifier to display the temperature in Fahrenheit, and the "K" format specifier to display the temperature in Kelvin.

using System;
using System.Globalization;

namespace HotAndCold
{

    public class Temperature : IFormattable
    {
        private decimal m_Temp;

        public Temperature(decimal temperature)
        {
            this.m_Temp = temperature;
        }

        public decimal Celsius
        {
            get { return this.m_Temp; }
        }

        public decimal Kelvin
        {
            get { return this.m_Temp + 273.15m; }
        }

        public decimal Fahrenheit
        {
            get { return Math.Round((decimal)this.m_Temp * 9 / 5 + 32, 2); }
        }

        public override string ToString()
        {
            return this.ToString("G", null);
        }

        public string ToString(string format)
        {
            return this.ToString(format, null);
        }

        public string ToString(string format, IFormatProvider provider)
        {
            // Handle null or empty arguments.
            if (String.IsNullOrEmpty(format))
                format = "G";
            // Remove any white space and covert to uppercase.
            format = format.Trim().ToUpperInvariant();

            if (provider == null)
                provider = NumberFormatInfo.CurrentInfo;

            switch (format)
            {
                // Convert temperature to Fahrenheit and return string.
                case "F":
                    return this.Fahrenheit.ToString("N2", provider) + "°F";
                // Convert temperature to Kelvin and return string.
                case "K":
                    return this.Kelvin.ToString("N2", provider) + "K";
                // Return temperature in Celsius.
                case "C":
                case "G":
                    return this.Celsius.ToString("N2", provider) + "°C";
                default:
                    throw new FormatException(String.Format("The '{0}' format string is not supported.", format));
            }
        }
    }

Public Class Temperature : Implements IFormattable
    Private m_Temp As Decimal

    Public Sub New(temperature As Decimal)
        Me.m_Temp = temperature
    End Sub

    Public ReadOnly Property Celsius() As Decimal
        Get
            Return Me.m_Temp
        End Get
    End Property

    Public ReadOnly Property Kelvin() As Decimal
        Get
            Return Me.m_Temp + 273.15D
        End Get
    End Property

    Public ReadOnly Property Fahrenheit() As Decimal
        Get
            Return Math.Round(CDec(Me.m_Temp * 9 / 5 + 32), 2)
        End Get
    End Property

    Public Overrides Function ToString() As String
        Return Me.ToString("G", Nothing)
    End Function

    Public Overloads Function ToString(format As String) As String
        Return Me.ToString(format, Nothing)
    End Function

    Public Overloads Function ToString(format As String, provider As IFormatProvider) As String _
       Implements IFormattable.ToString

        ' Handle null or empty arguments.
        If String.IsNullOrEmpty(format) Then format = "G"
        ' Remove any white space and convert to uppercase.
        format = format.Trim().ToUpperInvariant()

        If provider Is Nothing Then provider = NumberFormatInfo.CurrentInfo

        Select Case format
     ' Convert temperature to Fahrenheit and return string.
            Case "F"
                Return Me.Fahrenheit.ToString("N2", provider) & "°F"
     ' Convert temperature to Kelvin and return string.
            Case "K"
                Return Me.Kelvin.ToString("N2", provider) & "K"
     ' Return temperature in Celsius.
            Case "C", "G"
                Return Me.Celsius.ToString("N2", provider) & "°C"
            Case Else
                Throw New FormatException(String.Format($"The '{format}' format string is not supported."))
        End Select
    End Function
End Class

The following example instantiates a Temperature object. It then calls the ToString method and uses several composite format strings to obtain different string representations of a Temperature object. Each of these method calls, in turn, calls the IFormattable implementation of the Temperature class.

public class Example11
{
    public static void Main()
    {
        CultureInfo.CurrentCulture = CultureInfo.GetCultureInfo("en-US");
        Temperature temp = new Temperature(22m);
        Console.WriteLine(Convert.ToString(temp, new CultureInfo("ja-JP")));
        Console.WriteLine("Temperature: {0:K}", temp);
        Console.WriteLine("Temperature: {0:F}", temp);
        Console.WriteLine(String.Format(new CultureInfo("fr-FR"), "Temperature: {0:F}", temp));
    }
}
// The example displays the following output:
//       22.00°C
//       Temperature: 295.15K
//       Temperature: 71.60°F
//       Temperature: 71,60°F

Public Module Example12
    Public Sub Main12()
        Dim temp As New Temperature(22D)
        CultureInfo.CurrentCulture = CultureInfo.GetCultureInfo("en-US")
        Console.WriteLine(Convert.ToString(temp, New CultureInfo("ja-JP")))
        Console.WriteLine($"Temperature: {temp:K}")
        Console.WriteLine($"Temperature: {temp:F}")
        Console.WriteLine(String.Format(New CultureInfo("fr-FR"), $"Temperature: {temp:F}"))
    End Sub
End Module
' The example displays the following output:
'       22.00°C
'       Temperature: 295.15K
'       Temperature: 71.60°F
'       Temperature: 71,60°F

Composite formatting

Some methods, such as String.Format and StringBuilder.AppendFormat, support composite formatting. A composite format string is a kind of template that returns a single string that incorporates the string representation of zero, one, or more objects. Each object is represented in the composite format string by an indexed format item. The index of the format item corresponds to the position of the object that it represents in the method's parameter list. Indexes are zero-based. For example, in the following call to the String.Format method, the first format item, {0:D}, is replaced by the string representation of thatDate; the second format item, {1}, is replaced by the string representation of item1; and the third format item, {2:C2}, is replaced by the string representation of item1.Value.

result = String.Format("On {0:d}, the inventory of {1} was worth {2:C2}.",
                       thatDate, item1, item1.Value);
Console.WriteLine(result);
// The example displays output like the following if run on a system
// whose current culture is en-US:
//       On 5/1/2009, the inventory of WidgetA was worth $107.44.

result = String.Format("On {0:d}, the inventory of {1} was worth {2:C2}.",
                       thatDate, item1, item1.Value)
Console.WriteLine(result)
' The example displays output like the following if run on a system
' whose current culture is en-US:
'       On 5/1/2009, the inventory of WidgetA was worth $107.44.

In addition to replacing a format item with the string representation of its corresponding object, format items also let you control the following:

• The specific way in which an object is represented as a string, if the object implements the IFormattable interface and supports format strings. You do this by following the format item's index with a : (colon) followed by a valid format string. The previous example did this by formatting a date value with the "d" (short date pattern) format string (for example, {0:d}) and by formatting a numeric value with the "C2" format string (for example, {2:C2} to represent the number as a currency value with two fractional decimal digits.

• The width of the field that contains the object's string representation, and the alignment of the string representation in that field. You do this by following the format item's index with a , (comma) followed the field width. The string is right-aligned in the field if the field width is a positive value, and it is left-aligned if the field width is a negative value. The following example left-aligns date values in a 20-character field, and it right-aligns decimal values with one fractional digit in an 11-character field.

  DateTime startDate = new DateTime(2015, 8, 28, 6, 0, 0);
  decimal[] temps = { 73.452m, 68.98m, 72.6m, 69.24563m,
                     74.1m, 72.156m, 72.228m };
  Console.WriteLine("{0,-20} {1,11}\n", "Date", "Temperature");
  for (int ctr = 0; ctr < temps.Length; ctr++)
     Console.WriteLine("{0,-20:g} {1,11:N1}", startDate.AddDays(ctr), temps[ctr]);
  
  // The example displays the following output:
  //       Date                 Temperature
  //
  //       8/28/2015 6:00 AM           73.5
  //       8/29/2015 6:00 AM           69.0
  //       8/30/2015 6:00 AM           72.6
  //       8/31/2015 6:00 AM           69.2
  //       9/1/2015 6:00 AM            74.1
  //       9/2/2015 6:00 AM            72.2
  //       9/3/2015 6:00 AM            72.2
  

  Dim startDate As New Date(2015, 8, 28, 6, 0, 0)
  Dim temps() As Decimal = {73.452, 68.98, 72.6, 69.24563,
                             74.1, 72.156, 72.228}
  Console.WriteLine("{0,-20} {1,11}", "Date", "Temperature")
  Console.WriteLine()
  For ctr As Integer = 0 To temps.Length - 1
      Console.WriteLine("{0,-20:g} {1,11:N1}", startDate.AddDays(ctr), temps(ctr))
  Next
  ' The example displays the following output:
  '       Date                 Temperature
  '
  '       8/28/2015 6:00 AM           73.5
  '       8/29/2015 6:00 AM           69.0
  '       8/30/2015 6:00 AM           72.6
  '       8/31/2015 6:00 AM           69.2
  '       9/1/2015 6:00 AM            74.1
  '       9/2/2015 6:00 AM            72.2
  '       9/3/2015 6:00 AM            72.2
  

  Note that, if both the alignment string component and the format string component are present, the former precedes the latter (for example, {0,-20:g}.

For more information about composite formatting, see Composite Formatting.

Custom formatting with ICustomFormatter

Two composite formatting methods, String.Format(IFormatProvider, String, Object[]) and StringBuilder.AppendFormat(IFormatProvider, String, Object[]), include a format provider parameter that supports custom formatting. When either of these formatting methods is called, it passes a Type object that represents an ICustomFormatter interface to the format provider's GetFormat method. The GetFormat method is then responsible for returning the ICustomFormatter implementation that provides custom formatting.

The ICustomFormatter interface has a single method, Format(String, Object, IFormatProvider), that is called automatically by a composite formatting method, once for each format item in a composite format string. The Format(String, Object, IFormatProvider) method has three parameters: a format string, which represents the formatString argument in a format item, an object to format, and an IFormatProvider object that provides formatting services. Typically, the class that implements ICustomFormatter also implements IFormatProvider, so this last parameter is a reference to the custom formatting class itself. The method returns a custom formatted string representation of the object to be formatted. If the method cannot format the object, it should return a null reference (Nothing in Visual Basic).

The following example provides an ICustomFormatter implementation named ByteByByteFormatter that displays integer values as a sequence of two-digit hexadecimal values followed by a space.

public class ByteByByteFormatter : IFormatProvider, ICustomFormatter
{
   public object GetFormat(Type formatType)
   {
      if (formatType == typeof(ICustomFormatter))
         return this;
      else
         return null;
   }

   public string Format(string format, object arg,
                          IFormatProvider formatProvider)
   {
      if (! formatProvider.Equals(this)) return null;

      // Handle only hexadecimal format string.
      if (! format.StartsWith("X")) return null;

      byte[] bytes;
      string output = null;

      // Handle only integral types.
      if (arg is Byte)
         bytes = BitConverter.GetBytes((Byte) arg);
      else if (arg is Int16)
         bytes = BitConverter.GetBytes((Int16) arg);
      else if (arg is Int32)
         bytes = BitConverter.GetBytes((Int32) arg);
      else if (arg is Int64)
         bytes = BitConverter.GetBytes((Int64) arg);
      else if (arg is SByte)
         bytes = BitConverter.GetBytes((SByte) arg);
      else if (arg is UInt16)
         bytes = BitConverter.GetBytes((UInt16) arg);
      else if (arg is UInt32)
         bytes = BitConverter.GetBytes((UInt32) arg);
      else if (arg is UInt64)
         bytes = BitConverter.GetBytes((UInt64) arg);
      else
         return null;

      for (int ctr = bytes.Length - 1; ctr >= 0; ctr--)
         output += String.Format("{0:X2} ", bytes[ctr]);

      return output.Trim();
   }
}

Public Class ByteByByteFormatter : Implements IFormatProvider, ICustomFormatter
    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

        If Not formatProvider.Equals(Me) Then Return Nothing

        ' Handle only hexadecimal format string.
        If Not fmt.StartsWith("X") Then
            Return Nothing
        End If

        ' Handle only integral types.
        If Not typeof arg Is Byte AndAlso
           Not typeof arg Is Int16 AndAlso
           Not typeof arg Is Int32 AndAlso
           Not typeof arg Is Int64 AndAlso
           Not typeof arg Is SByte AndAlso
           Not typeof arg Is UInt16 AndAlso
           Not typeof arg Is UInt32 AndAlso
           Not typeof arg Is UInt64 Then _
              Return Nothing

        Dim bytes() As Byte = BitConverter.GetBytes(arg)
        Dim output As String = Nothing

        For ctr As Integer = bytes.Length - 1 To 0 Step -1
            output += String.Format("{0:X2} ", bytes(ctr))
        Next

        Return output.Trim()
    End Function
End Class

The following example uses the ByteByByteFormatter class to format integer values. Note that the ICustomFormatter.Format method is called more than once in the second String.Format(IFormatProvider, String, Object[]) method call, and that the default NumberFormatInfo provider is used in the third method call because the .ByteByByteFormatter.Format method does not recognize the "N0" format string and returns a null reference (Nothing in Visual Basic).

public class Example10
{
   public static void Main()
   {
      long value = 3210662321;
      byte value1 = 214;
      byte value2 = 19;

      Console.WriteLine(String.Format(new ByteByByteFormatter(), "{0:X}", value));
      Console.WriteLine(String.Format(new ByteByByteFormatter(), "{0:X} And {1:X} = {2:X} ({2:000})",
                                      value1, value2, value1 & value2));
      Console.WriteLine(String.Format(new ByteByByteFormatter(), "{0,10:N0}", value));
   }
}
// The example displays the following output:
//       00 00 00 00 BF 5E D1 B1
//       00 D6 And 00 13 = 00 12 (018)
//       3,210,662,321

Public Module Example10
    Public Sub Main10()
        Dim value As Long = 3210662321
        Dim value1 As Byte = 214
        Dim value2 As Byte = 19

        Console.WriteLine((String.Format(New ByteByByteFormatter(), "{0:X}", value)))
        Console.WriteLine((String.Format(New ByteByByteFormatter(), "{0:X} And {1:X} = {2:X} ({2:000})",
                                        value1, value2, value1 And value2)))
        Console.WriteLine(String.Format(New ByteByByteFormatter(), "{0,10:N0}", value))
    End Sub
End Module
' The example displays the following output:
'       00 00 00 00 BF 5E D1 B1
'       00 D6 And 00 13 = 00 12 (018)
'       3,210,662,321

See also

Title	Definition
Standard Numeric Format Strings	Describes standard format strings that create commonly used string representations of numeric values.
Custom Numeric Format Strings	Describes custom format strings that create application-specific formats for numeric values.
Standard Date and Time Format Strings	Describes standard format strings that create commonly used string representations of DateTime values.
Custom Date and Time Format Strings	Describes custom format strings that create application-specific formats for DateTime values.
Standard TimeSpan Format Strings	Describes standard format strings that create commonly used string representations of time intervals.
Custom TimeSpan Format Strings	Describes custom format strings that create application-specific formats for time intervals.
Enumeration Format Strings	Describes standard format strings that are used to create string representations of enumeration values.
Composite Formatting	Describes how to embed one or more formatted values in a string. The string can subsequently be displayed on the console or written to a stream.
Parsing Strings	Describes how to initialize objects to the values described by string representations of those objects. Parsing is the inverse operation of formatting.

Reference

• System.IFormattable
• System.IFormatProvider
• System.ICustomFormatter