IFormatProvider.GetFormat(Type) Método

Definición

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

public:
 System::Object ^ GetFormat(Type ^ formatType);
public object GetFormat (Type formatType);
abstract member GetFormat : Type -> obj
Public Function GetFormat (formatType As Type) As Object

Parámetros

formatType
Type

Objeto que especifica el tipo de objeto de formato que se va a devolver.An object that specifies the type of format object to return.

Devoluciones

Instancia del objeto especificado por formatType si la implementación de IFormatProvider puede proporcionar ese tipo de objeto; de lo contrario, devuelve null.An instance of the object specified by formatType, if the IFormatProvider implementation can supply that type of object; otherwise, null.

Ejemplos

En el ejemplo siguiente se muestra el uso de una clase que implementa la interfaz IFormatProvider y el método GetFormat.The following example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. La clase AcctNumberFormat convierte un valor Int64 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 método GetFormat devuelve una referencia a sí misma si el parámetro formatType hace referencia a una clase que implementa ICustomFormatter; de lo contrario, GetFormat devuelve null.Its GetFormat method returns a reference to itself 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

Una instancia de la clase AcctNumberFormat se puede pasar como argumento a un método que proporciona servicios de formato o análisis.An instance of the AcctNumberFormat class can then be passed as an argument to a method that provides formatting or parsing services. Por ejemplo, el código siguiente pasa una clase AcctNumberFormat al método String.Format(IFormatProvider, String, Object[]) para generar un número de cuenta de 12 dígitos con formato.For example, the following code passes an AcctNumberFormat class to the String.Format(IFormatProvider, String, Object[]) method to generate 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

GetFormat es un método de devolución de llamada que invoca los métodos de formato y análisis para recuperar información sobre el formato de la cadena de entrada en operaciones de análisis o el formato de la cadena de salida en operaciones de formato.GetFormat is a callback method that formatting and parsing methods invoke to retrieve information about the format of the input string in parsing operations or the format of the output string in formatting operations. En el parámetro formatType, el método de formato o análisis pasa el tipo de objeto que requiere para realizar su operación.In the formatType parameter, the formatting or parsing method passes the type of object it requires to perform its operation. Si la implementación de IFormatProvider puede proporcionar este objeto de formato o análisis, devuelve ese objeto.If the IFormatProvider implementation can supply this formatting or parsing object, it returns that object. En caso contrario, devuelve null.If not, it returns null.

Por ejemplo, en la llamada al método Int32.ToString(IFormatProvider), el argumento del método es un objeto IFormatProvider que proporciona información sobre cómo se puede dar formato a la representación en forma de cadena de la instancia de entero actual.For example, in the call to the Int32.ToString(IFormatProvider) method, the method argument is an IFormatProvider object that provides information about how the string representation of the current integer instance might be formatted. Cuando el tiempo de ejecución ejecuta el método, llama al método GetFormat del objeto IFormatProvider y le pasa un objeto Type que representa el tipo de NumberFormatInfo.When the runtime executes the method, it calls the IFormatProvider object's GetFormat method and passes it a Type object that represents the NumberFormatInfo type. Si el objeto IFormatProvider puede proporcionar un objeto NumberFormatInfo, devuelve ese objeto.If the IFormatProvider object can supply a NumberFormatInfo object, it returns that object. Si no puede proporcionar un objeto de ese tipo, devuelve null.If it cannot supply an object of that type, it returns null.

Puede implementar la interfaz IFormatProvider y el método GetFormat en las clases que proporcionan servicios de formato o análisis personalizados.You can implement the IFormatProvider interface and the GetFormat method in classes that provide custom formatting or parsing services. A continuación, la implementación de IFormatProvider se pasa como argumento a cualquier sobrecarga de un método de análisis o formato que tenga un parámetro de tipo IFormatProvider, como String.Format(IFormatProvider, String, Object[]), Int32.ToString(String, IFormatProvider)o DateTime.Parse(String, IFormatProvider).The IFormatProvider implementation is then passed as an argument to any overload of a parsing or formatting method that has a parameter of type IFormatProvider, such as String.Format(IFormatProvider, String, Object[]), Int32.ToString(String, IFormatProvider), or DateTime.Parse(String, IFormatProvider).

Se aplica a