IFormatProvider Interfaz

Definición

Proporciona un mecanismo para recuperar un objeto con el fin de controlar el formato.Provides a mechanism for retrieving an object to control formatting.

public interface class IFormatProvider
[System.Runtime.InteropServices.ComVisible(true)]
public interface IFormatProvider
type IFormatProvider = interface
Public Interface IFormatProvider
Derivado
Atributos

Ejemplos

En el ejemplo siguiente se muestra cómo IFormatProvider una implementación de puede cambiar la representación de un valor de fecha y hora.The following example illustrates how an IFormatProvider implementation can change the representation of a date and time value. En este caso, se muestra una sola fecha mediante el CultureInfo uso de objetos que representan cuatro referencias culturales diferentes.In this case, a single date is displayed by using CultureInfo objects that represent four different cultures.

using System;
using System.Globalization;

public class Example
{
   public static void Main()
   {
      DateTime dateValue = new DateTime(2009, 6, 1, 16, 37, 0);
      CultureInfo[] cultures = { new CultureInfo("en-US"), 
                                 new CultureInfo("fr-FR"),
                                 new CultureInfo("it-IT"),
                                 new CultureInfo("de-DE") };
      foreach (CultureInfo culture in cultures)
         Console.WriteLine("{0}: {1}", culture.Name, dateValue.ToString(culture));
   }
}
// The example displays the following output:
//       en-US: 6/1/2009 4:37:00 PM
//       fr-FR: 01/06/2009 16:37:00
//       it-IT: 01/06/2009 16.37.00
//       de-DE: 01.06.2009 16:37:00
Imports System.Globalization

Module Example
   Public Sub Main()
      Dim dateValue As Date = #06/01/2009 4:37PM#
      Dim cultures() As CultureInfo = {New CultureInfo("en-US"), _
                                       New CultureInfo("fr-FR"), _
                                       New CultureInfo("it-IT"), _
                                       New CultureInfo("de-DE") }
      For Each culture As CultureInfo In cultures
         Console.WriteLine("{0}: {1}", culture.Name, dateValue.ToString(culture))
      Next                                        
   End Sub
End Module
' The example displays the following output:
'       en-US: 6/1/2009 4:37:00 PM
'       fr-FR: 01/06/2009 16:37:00
'       it-IT: 01/06/2009 16.37.00
'       de-DE: 01.06.2009 16:37:00

En el ejemplo siguiente se muestra el uso de una clase que implementa la IFormatProvider interfaz y el GetFormat método.The following example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. La AcctNumberFormat clase convierte Int64 un valor que representa un número de cuenta en un número de cuenta de 12 dígitos con formato.The AcctNumberFormat class converts an Int64 value that represents an account number to a formatted 12-digit account number. Su GetFormat método devuelve una referencia a la instancia AcctNumberFormat actual si el formatType ICustomFormatterparámetro hace referencia a una clase que implementa; de lo GetFormat contrario null, devuelve.Its GetFormat method returns a reference to the current AcctNumberFormat instance if the formatType parameter refers to a class that implements ICustomFormatter; otherwise, GetFormat returns null.

public class AcctNumberFormat : IFormatProvider, ICustomFormatter
{
   private const int ACCT_LENGTH = 12;
   
   public object GetFormat(Type formatType)
   {
      if (formatType == typeof(ICustomFormatter))
         return this;
      else
         return null;
   }
   
   public string Format(string fmt, object arg, IFormatProvider formatProvider) 
   {
      // Provide default formatting if arg is not an Int64.
      if (arg.GetType() != typeof(Int64))
         try {
            return HandleOtherFormats(fmt, arg); 
         }
         catch (FormatException e) {
            throw new FormatException(String.Format("The format of '{0}' is invalid.", fmt), e);
         }
      
      // Provide default formatting for unsupported format strings.
      string ufmt = fmt.ToUpper(CultureInfo.InvariantCulture);
      if (! (ufmt == "H" || ufmt == "I")) 
         try {
            return HandleOtherFormats(fmt, arg);
         }
         catch (FormatException e) {
            throw new FormatException(String.Format("The format of '{0}' is invalid.", fmt), e);
         }
           
      // Convert argument to a string.
      string result = arg.ToString();
      
      // If account number is less than 12 characters, pad with leading zeroes.
      if (result.Length < ACCT_LENGTH)
         result = result.PadLeft(ACCT_LENGTH, '0');
      // If account number is more than 12 characters, truncate to 12 characters.
      if (result.Length > ACCT_LENGTH)
         result = result.Substring(0, ACCT_LENGTH);   

      if (ufmt == "I")                    // Integer-only format. 
         return result;
      // Add hyphens for H format specifier.
      else                                         // Hyphenated format.
         return result.Substring(0, 5) + "-" + result.Substring(5, 3) + "-" + result.Substring(8);
   }

   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;
   }
}
Public Class AcctNumberFormat : Implements IFormatProvider, ICustomFormatter

   Private Const ACCT_LENGTH As Integer = 12
   
   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

      ' Provide default formatting if arg is not an Int64.
       If Not TypeOf arg Is Int64 Then
         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   
                     
      ' Provider default formatting for unsupported format strings.
      Dim ufmt As String = fmt.ToUpper(CultureInfo.InvariantCulture)
      If Not (ufmt = "H" Or ufmt = "I") Then
         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   

      ' Convert argument to a string.
      Dim result As String = arg.ToString()
      
      ' If account number is less than 12 characters, pad with leading zeroes.
      If result.Length < ACCT_LENGTH Then result = result.PadLeft(ACCT_LENGTH, "0"c)
      ' If account number is more than 12 characters, truncate to 12 characters.
      If result.Length > ACCT_LENGTH Then result = Left(result, ACCT_LENGTH)   
      
      If ufmt = "I"                              ' Integer-only format.
         Return result
      ' Add hyphens for H format specifier.
      Else                                       ' Hypenated format.
         Return Left(result, 5) & "-" & Mid(result, 6, 3) & "-" & Right(result, 4)
      End If   
   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

La clase que implementa IFormatProvider se puede usar en una llamada a una operación de formato y análisis.The class that implements IFormatProvider can then be used in a call to a formatting and parsing operation. Por ejemplo, el código siguiente llama String.Format(IFormatProvider, String, Object[]) al método para generar una cadena que contiene un número de cuenta de 12 dígitos con formato.For example, the following code calls the String.Format(IFormatProvider, String, Object[]) method to generate a string that contains a formatted 12-digit account number.

using System;
using System.Globalization;

public enum DaysOfWeek { Monday=1, Tuesday=2 };

public class TestFormatting
{
   public static void Main()
   {
      long acctNumber;
      double balance; 
      DaysOfWeek wday; 
      string output;

      acctNumber = 104254567890;
      balance = 16.34;
      wday = DaysOfWeek.Monday;

      output = String.Format(new AcctNumberFormat(), 
                             "On {2}, the balance of account {0:H} was {1:C2}.", 
                             acctNumber, balance, wday);
      Console.WriteLine(output);

      wday = DaysOfWeek.Tuesday;
      output = String.Format(new AcctNumberFormat(), 
                             "On {2}, the balance of account {0:I} was {1:C2}.", 
                             acctNumber, balance, wday);
      Console.WriteLine(output);
   }
}
// The example displays the following output:
//       On Monday, the balance of account 10425-456-7890 was $16.34.
//       On Tuesday, the balance of account 104254567890 was $16.34.
Imports System.Globalization

Public Enum DaysOfWeek As Long
   Monday = 1
   Tuesday = 2
End Enum

Module TestFormatting
   Public Sub Main()
      Dim acctNumber As Long, balance As Double 
      Dim wday As DaysOfWeek 
      Dim output As String

      acctNumber = 104254567890
      balance = 16.34
      wday = DaysOfWeek.Monday

      output = String.Format(New AcctNumberFormat(), "On {2}, the balance of account {0:H} was {1:C2}.", acctNumber, balance, wday)
      Console.WriteLine(output)

      wday = DaysOfWeek.Tuesday
      output = String.Format(New AcctNumberFormat(), "On {2}, the balance of account {0:I} was {1:C2}.", acctNumber, balance, wday)
      Console.WriteLine(output)
   End Sub
End Module
' The example displays the following output:
'    On Monday, the balance of account 10425-456-7890 was $16.34.
'    On Tuesday, the balance of account 104254567890 was $16.34.

Comentarios

La IFormatProvider interfaz proporciona un objeto que proporciona información de formato para las operaciones de formato y análisis.The IFormatProvider interface supplies an object that provides formatting information for formatting and parsing operations. Las operaciones de formato convierten el valor de un tipo en la representación de cadena de ese valor.Formatting operations convert the value of a type to the string representation of that value. Los métodos de formato típicos ToString son los métodos de un tipo, así Formatcomo.Typical formatting methods are the ToString methods of a type, as well as Format. Las operaciones de análisis convierten la representación de cadena de un valor en un tipo con ese valor.Parsing operations convert the string representation of a value to a type with that value. Los métodos de análisis Parse típicos TryParseson y.Typical parsing methods are Parse and TryParse.

La IFormatProvider interfaz está formada por un único método IFormatProvider.GetFormat,.The IFormatProvider interface consists of a single method, IFormatProvider.GetFormat. GetFormates un método de devolución de llamada: El método de análisis o formato lo llama y le pasa Type un objeto que representa el tipo de objeto que el método de formato o análisis espera que proporcione información de formato.GetFormat is a callback method: The parsing or formatting method calls it and passes it a Type object that represents the type of object that the formatting or parsing method expects will provide formatting information. El GetFormat método es responsable de devolver un objeto de ese tipo.The GetFormat method is responsible for returning an object of that type.

IFormatProviderlas implementaciones suelen usarse implícitamente mediante métodos de análisis y formato.IFormatProvider implementations are often used implicitly by formatting and parsing methods. Por ejemplo, el DateTime.ToString(String) método usa implícitamente una IFormatProvider implementación de que representa la referencia cultural actual del sistema.For example, the DateTime.ToString(String) method implicitly uses an IFormatProvider implementation that represents the system's current culture. IFormatProviderlas implementaciones también se pueden especificar explícitamente mediante métodos que tienen un parámetro IFormatProviderde tipo, Int32.Parse(String, IFormatProvider) como String.Format(IFormatProvider, String, Object[])y.IFormatProvider implementations can also be specified explicitly by methods that have a parameter of type IFormatProvider, such as Int32.Parse(String, IFormatProvider) and String.Format(IFormatProvider, String, Object[]).

El .NET Framework incluye las tres implementaciones predefinidas IFormatProvider siguientes para proporcionar información específica de la referencia cultural que se usa para dar formato o analizar valores numéricos y de fecha y hora:The .NET Framework includes the following three predefined IFormatProvider implementations to provide culture-specific information that is used in formatting or parsing numeric and date and time values:

La .NET Framework también admite el formato personalizado.The .NET Framework also supports custom formatting. Normalmente, esto implica la creación de una clase de formato que implementa IFormatProvider y ICustomFormatter.This typically involves the creation of a formatting class that implements both IFormatProvider and ICustomFormatter. A continuación, se pasa una instancia de esta clase como un parámetro a un método que realiza una operación de formato personalizada String.Format(IFormatProvider, String, Object[]) , como en el ejemplo se proporciona una ilustración de este tipo de implementación personalizada que da formato a un número como un número de cuenta de 12 dígitos.An instance of this class is then passed as a parameter to a method that performs a custom formatting operation, such as String.Format(IFormatProvider, String, Object[]) The example provides an illustration of such a custom implementation that formats a number as a 12-digit account number.

Métodos

GetFormat(Type)

Devuelve un objeto que proporciona servicios de formato para el tipo especificado.Returns an object that provides formatting services for the specified type.

Se aplica a

Consulte también: