ICustomFormatter.Format(String, Object, IFormatProvider) Méthode

Définition

Convertit la valeur d’un objet spécifié en représentation sous forme de chaîne équivalente en utilisant les informations de format et de mise en forme spécifiques à la culture spécifiées.Converts the value of a specified object to an equivalent string representation using specified format and culture-specific formatting information.

public:
 System::String ^ Format(System::String ^ format, System::Object ^ arg, IFormatProvider ^ formatProvider);
public string Format (string format, object arg, IFormatProvider formatProvider);
public string? Format (string format, object arg, IFormatProvider formatProvider);
abstract member Format : string * obj * IFormatProvider -> string
Public Function Format (format As String, arg As Object, formatProvider As IFormatProvider) As String

Paramètres

format
String

Chaîne de format contenant des spécifications de mise en forme.A format string containing formatting specifications.

arg
Object

Objet à mettre en forme.An object to format.

formatProvider
IFormatProvider

Objet qui fournit des informations de format sur l’instance actuelle.An object that supplies format information about the current instance.

Retours

String

Représentation sous forme de chaîne de la valeur de arg, mise en forme comme spécifiée par format et formatProvider.The string representation of the value of arg, formatted as specified by format and formatProvider.

Exemples

L’exemple suivant implémente ICustomFormatter pour autoriser le formatage binaire, octal et hexadécimal des valeurs intégrales.The following example implements ICustomFormatter to allow binary, octal, and hexadecimal formatting of integral values. Son ICustomFormatter.Format implémentation détermine si le paramètre de format est l’une des trois chaînes de format prises en charge (« B » pour Binary, « O » pour octal et « H » pour hexadécimal) et met en forme le arg paramètre de manière appropriée.Its ICustomFormatter.Format implementation determines whether the format parameter is one of the three supported format strings ("B" for binary, "O" for octal, and "H" for hexadecimal) and formats the arg parameter appropriately. Sinon, si arg n’est pas null , il appelle l' arg implémentation du paramètre IFormattable.ToString , le cas échéant, ou sa méthode sans paramètre ToString , si ce n’est pas le cas.Otherwise, if arg is not null, it calls the arg parameter's IFormattable.ToString implementation, if one exists, or its parameterless ToString method, if one does not. Si arg est null, la méthode retourne String.Empty.If arg is null, the method returns String.Empty.

using System;
using System.Globalization;
using System.Numerics;

public class BinaryFormatter : IFormatProvider, ICustomFormatter
{
   // IFormatProvider.GetFormat implementation.
   public object GetFormat(Type formatType)
   {
      // Determine whether custom formatting object is requested.
      if (formatType == typeof(ICustomFormatter))
         return this;
      else
         return null;
   }

   // Format number in binary (B), octal (O), or hexadecimal (H).
   public string Format(string format, object arg, IFormatProvider formatProvider)
   {
      // Handle format string.
      int baseNumber;
      // Handle null or empty format string, string with precision specifier.
      string thisFmt = String.Empty;
      // Extract first character of format string (precision specifiers
      // are not supported).
      if (! String.IsNullOrEmpty(format))
         thisFmt = format.Length > 1 ? format.Substring(0, 1) : format;

      // Get a byte array representing the numeric value.
      byte[] bytes;
      if (arg is sbyte)
      {
         string byteString = ((sbyte) arg).ToString("X2");
         bytes = new byte[1] { Byte.Parse(byteString, System.Globalization.NumberStyles.HexNumber ) };
      }
      else if (arg is byte) {
         bytes = new byte[1] { (byte) arg };
      }
      else if (arg is short) {
         bytes = BitConverter.GetBytes((short) arg);
      }
      else if (arg is int) {
         bytes = BitConverter.GetBytes((int) arg);
      }
      else if (arg is long) {
         bytes = BitConverter.GetBytes((long) arg);
      }
      else if (arg is ushort) {
         bytes = BitConverter.GetBytes((ushort) arg);
      }
      else if (arg is uint) {
         bytes = BitConverter.GetBytes((uint) arg);
      }
      else if (arg is ulong) {
         bytes = BitConverter.GetBytes((ulong) arg);
      }
      else if (arg is BigInteger) {
         bytes = ((BigInteger) arg).ToByteArray();
      }
      else {
         try {
            return HandleOtherFormats(format, arg);
         }
         catch (FormatException e) {
            throw new FormatException(String.Format("The format of '{0}' is invalid.", format), e);
         }
      }

      switch (thisFmt.ToUpper())
      {
         // Binary formatting.
         case "B":
            baseNumber = 2;
            break;
         case "O":
            baseNumber = 8;
            break;
         case "H":
            baseNumber = 16;
            break;
         // Handle unsupported format strings.
         default:
         try {
            return HandleOtherFormats(format, arg);
         }
         catch (FormatException e) {
            throw new FormatException(String.Format("The format of '{0}' is invalid.", format), e);
         }
      }

      // Return a formatted string.
      string numericString = String.Empty;
      for (int ctr = bytes.GetUpperBound(0); ctr >= bytes.GetLowerBound(0); ctr--)
      {
         string byteString = Convert.ToString(bytes[ctr], baseNumber);
         if (baseNumber == 2)
            byteString = new String('0', 8 - byteString.Length) + byteString;
         else if (baseNumber == 8)
            byteString = new String('0', 4 - byteString.Length) + byteString;
         // Base is 16.
         else
            byteString = new String('0', 2 - byteString.Length) + byteString;

         numericString +=  byteString + " ";
      }
      return numericString.Trim();
   }

   private string HandleOtherFormats(string format, object arg)
   {
      if (arg is IFormattable)
         return ((IFormattable)arg).ToString(format, CultureInfo.CurrentCulture);
      else if (arg != null)
         return arg.ToString();
      else
         return String.Empty;
   }
}
Imports System.Globalization
Imports System.Numerics

Public Class BinaryFormatter : Implements IFormatProvider, ICustomFormatter
   ' IFormatProvider.GetFormat implementation.
   Public Function GetFormat(formatType As Type) As Object _
                   Implements IFormatProvider.GetFormat
      ' Determine whether custom formatting object is requested.
      If formatType Is GetType(ICustomFormatter) Then
         Return Me
      Else
         Return Nothing
      End If
   End Function   

   ' Format number in binary (B), octal (O), or hexadecimal (H).
   Public Function Format(fmt As String, arg As Object, _
                          formatProvider As IFormatProvider) As String _
                   Implements ICustomFormatter.Format

     ' Handle format string.
      Dim base As Integer
      ' Handle null or empty format string, string with precision specifier.
      Dim thisFmt As String = String.Empty
      ' Extract first character of format string (precision specifiers
      ' are not supported by BinaryFormatter).
      If Not String.IsNullOrEmpty(fmt) Then
         thisFmt = CStr(IIf(fmt.Length > 1, fmt.Substring(0, 1), fmt))
      End If
         


      ' Get a byte array representing the numeric value.
      Dim bytes() As Byte
      If TypeOf(arg) Is SByte Then
         Dim byteString As String = CType(arg, SByte).ToString("X2")
         bytes = New Byte(0) { Byte.Parse(byteString, System.Globalization.NumberStyles.HexNumber ) }
      ElseIf TypeOf(arg) Is Byte Then
         bytes = New Byte(0) { CType(arg, Byte) }
      ElseIf TypeOf(arg) Is Int16 Then
         bytes = BitConverter.GetBytes(CType(arg, Int16))
      ElseIf TypeOf(arg) Is Int32 Then
         bytes = BitConverter.GetBytes(CType(arg, Int32))
      ElseIf TypeOf(arg) Is Int64 Then
         bytes = BitConverter.GetBytes(CType(arg, Int64))
      ElseIf TypeOf(arg) Is UInt16 Then
         bytes = BitConverter.GetBytes(CType(arg, UInt16))
      ElseIf TypeOf(arg) Is UInt32 Then
         bytes = BitConverter.GetBytes(CType(arg, UInt64))
      ElseIf TypeOf(arg) Is UInt64 Then
         bytes = BitConverter.GetBytes(CType(arg, UInt64))                  
      ElseIf TypeOf(arg) Is BigInteger Then
         bytes = CType(arg, BigInteger).ToByteArray()
      Else
         Try 
            Return HandleOtherFormats(fmt, arg) 
         Catch e As FormatException 
            Throw New FormatException(String.Format("The format of '{0}' is invalid.", fmt), e)
         End Try
      End If

      Select Case thisFmt.ToUpper()
         ' Binary formatting.
         Case "B"
            base = 2        
         Case "O"
            base = 8
         Case "H"
            base = 16
         ' Handle unsupported format strings.
         Case Else
            Try 
               Return HandleOtherFormats(fmt, arg) 
            Catch e As FormatException 
               Throw New FormatException(String.Format("The format of '{0}' is invalid.", fmt), e)
            End Try
      End Select
      
      ' Return a formatted string.
      Dim numericString As String = String.Empty
      For ctr As Integer = bytes.GetUpperBound(0) To bytes.GetLowerBound(0) Step -1
         Dim byteString As String = Convert.ToString(bytes(ctr), base)
         If base = 2 Then
            byteString = New String("0"c, 8 - byteString.Length) + byteString
         ElseIf base = 8 Then
            byteString = New String("0"c, 4 - byteString.Length) + byteString
         ' Base is 16.
         Else     
            byteString = New String("0"c, 2 - byteString.Length) + byteString
         End If
         numericString +=  byteString + " "
      Next
      Return numericString.Trim()
   End Function
   
   Private Function HandleOtherFormats(fmt As String, arg As Object) As String
      If TypeOf arg Is IFormattable Then
         Return DirectCast(arg, IFormattable).ToString(fmt, CultureInfo.CurrentCulture)
      ElseIf arg IsNot Nothing Then
         Return arg.ToString()
      Else
         Return String.Empty
      End If
   End Function
End Class

BinaryFormatter peut ensuite être utilisé pour fournir une mise en forme personnalisée en passant un BinaryFormatter objet comme provider paramètre de la Format méthode, comme le montre l’exemple suivant.BinaryFormatter can then be used to provide custom formatting by passing a BinaryFormatter object as the provider parameter of the Format method, as the following example shows.

public class Example
{
   public static void Main()
   {
      Console.WindowWidth = 100;

      byte byteValue = 124;
      Console.WriteLine(String.Format(new BinaryFormatter(),
                                      "{0} (binary: {0:B}) (hex: {0:H})", byteValue));

      int intValue = 23045;
      Console.WriteLine(String.Format(new BinaryFormatter(),
                                      "{0} (binary: {0:B}) (hex: {0:H})", intValue));

      ulong ulngValue = 31906574882;
      Console.WriteLine(String.Format(new BinaryFormatter(),
                                      "{0}\n   (binary: {0:B})\n   (hex: {0:H})",
                                      ulngValue));

      BigInteger bigIntValue = BigInteger.Multiply(Int64.MaxValue, 2);
      Console.WriteLine(String.Format(new BinaryFormatter(),
                                      "{0}\n   (binary: {0:B})\n   (hex: {0:H})",
                                      bigIntValue));
   }
}
// The example displays the following output:
//    124 (binary: 01111100) (hex: 7c)
//    23045 (binary: 00000000 00000000 01011010 00000101) (hex: 00 00 5a 05)
//    31906574882
//       (binary: 00000000 00000000 00000000 00000111 01101101 11000111 10110010 00100010)
//       (hex: 00 00 00 07 6d c7 b2 22)
//    18446744073709551614
//       (binary: 00000000 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111110)
//       (hex: 00 ff ff ff ff ff ff ff fe)
Public Module Example
   Public Sub Main
      Console.WindowWidth = 100
      
      Dim byteValue As Byte = 124
      Console.WriteLine(String.Format(New BinaryFormatter(), _
                                      "{0} (binary: {0:B}) (hex: {0:H})", byteValue))
      
      Dim intValue As Integer = 23045
      Console.WriteLine(String.Format(New BinaryFormatter(), _
                                      "{0} (binary: {0:B}) (hex: {0:H})", intValue))
      
      Dim ulngValue As ULong = 31906574882
      Console.WriteLine(String.Format(New BinaryFormatter(), _
                                      "{0} {1}   (binary: {0:B}) {1}   (hex: {0:H})", _
                                      ulngValue, vbCrLf))

      Dim bigIntValue As BigInteger = BigInteger.Multiply(Int64.MaxValue, 2)
      Console.WriteLine(String.Format(New BinaryFormatter(), _
                                      "{0} {1}   (binary: {0:B}) {1}   (hex: {0:H})", _
                                      bigIntValue, vbCrLf))
   End Sub
End Module
' The example displays the following output:
'    124 (binary: 01111100) (hex: 7c)
'    23045 (binary: 00000000 00000000 01011010 00000101) (hex: 00 00 5a 05)
'    31906574882
'       (binary: 00000000 00000000 00000000 00000111 01101101 11000111 10110010 00100010)
'       (hex: 00 00 00 07 6d c7 b2 22)
'    18446744073709551614
'       (binary: 00000000 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111110)
'       (hex: 00 ff ff ff ff ff ff ff fe)

Remarques

ICustomFormatter.Format est une méthode de rappel.ICustomFormatter.Format is a callback method. Elle est appelée par une méthode qui prend en charge la mise en forme personnalisée, telle que String.Format(IFormatProvider, String, Object[]) ou StringBuilder.AppendFormat(IFormatProvider, String, Object[]) .It is called by a method that supports custom formatting, such as String.Format(IFormatProvider, String, Object[]) or StringBuilder.AppendFormat(IFormatProvider, String, Object[]). L’implémentation est appelée une fois pour chaque élément de mise en forme dans une chaîne de format composite.The implementation is called once for each format item in a composite format string. Par exemple, dans l’instruction suivante, la ICustomFormatter.Format méthode est appelée trois fois.For example, in the following statement, the ICustomFormatter.Format method is called three times.

Console.WriteLine(String.Format(new BinaryFormatter(),
                                "{0} (binary: {0:B}) (hex: {0:H})", byteValue));
Console.WriteLine(String.Format(New BinaryFormatter(), _
                                "{0} (binary: {0:B}) (hex: {0:H})", byteValue))

Le arg paramètre est l’objet dans la liste d’objets dont la position de base zéro correspond à l’index d’un élément de format particulier.The arg parameter is the object in the object list whose zero-based position corresponds to the index of a particular format item.

Le format paramètre contient une chaîne de format, qui est le formatString composant d’un élément de format.The format parameter contains a format string, which is the formatString component of a format item. Si l’élément de mise en forme n’a pas de formatString composant, la valeur de format est null .If the format item has no formatString component, the value of format is null. Si format est null , selon le type de arg , vous pourrez peut-être utiliser la spécification de format par défaut de votre choix.If format is null, depending on the type of arg, you may be able to use the default format specification of your choice.

Le formatProvider paramètre correspond IFormatProvider à l’implémentation de qui fournit la mise en forme pour arg .The formatProvider parameter is the IFormatProvider implementation that provides formatting for arg. En règle générale, il s’agit d’une instance de votre ICustomFormatter implémentation.Typically, it is an instance of your ICustomFormatter implementation. Si formatProvider est null , ignorez ce paramètre.If formatProvider is null, ignore that parameter.

Votre implémentation de la Format méthode doit inclure les fonctionnalités suivantes afin que le .NET Framework puisse fournir une mise en forme que vous ne prenez pas en charge.Your implementation of the Format method must include the following functionality so the .NET Framework can provide formatting you do not support. Si votre méthode de format ne prend pas en charge un format, déterminez si l’objet mis en forme implémente l' IFormattable interface.If your format method does not support a format, determine whether the object being formatted implements the IFormattable interface. Si c’est le cas, appelez la IFormattable.ToString méthode de cette interface.If it does, invoke the IFormattable.ToString method of that interface. Sinon, appelez la méthode par défaut Object.ToString de l’objet sous-jacent.Otherwise, invoke the default Object.ToString method of the underlying object. Le code suivant illustre ce modèle.The following code illustrates this pattern.

if (arg is IFormattable)
   return ((IFormattable)arg).ToString(format, CultureInfo.CurrentCulture);
else if (arg != null)
   return arg.ToString();
If TypeOf arg Is IFormattable Then
   Return DirectCast(arg, IFormattable).ToString(fmt, CultureInfo.CurrentCulture)
ElseIf arg IsNot Nothing Then
   Return arg.ToString()

S’applique à

Voir aussi