IFormatProvider.GetFormat(Type) Method

Definition

Retorna um objeto que fornece serviços de formatação para o 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

Parameters

formatType
Type

Um objeto que especifica o tipo de objeto de formato a ser retornado.An object that specifies the type of format object to return.

Returns

Object

Uma instância do objeto especificado por formatType, se a implementação IFormatProvider pode fornecer esse tipo de objeto; caso contrário, null.An instance of the object specified by formatType, if the IFormatProvider implementation can supply that type of object; otherwise, null.

Examples

O exemplo a seguir ilustra o uso de uma classe que implementa a interface IFormatProvider e o método GetFormat.The following example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. A classe AcctNumberFormat converte um valor de Int64 que representa um número de conta para um número de conta de 12 dígitos formatado.The AcctNumberFormat class converts an Int64 value that represents an account number to a formatted 12-digit account number. Seu método GetFormat retorna uma referência a si mesmo se o parâmetro formatType se refere a uma classe que implementa ICustomFormatter; caso contrário, GetFormat retornará 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

Uma instância da classe AcctNumberFormat pode então ser passada como um argumento para um método que fornece formatação ou análise de serviços.An instance of the AcctNumberFormat class can then be passed as an argument to a method that provides formatting or parsing services. Por exemplo, o código a seguir passa uma classe AcctNumberFormat para o método String.Format(IFormatProvider, String, Object[]) para gerar um número de conta de 12 dígitos formatado.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.

Remarks

GetFormat é um método de retorno de chamada que os métodos de formatação e análise chamam para recuperar informações sobre o formato da cadeia de caracteres de entrada em operações de análise ou o formato da cadeia de caracteres de saída em operações de formatação.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. No parâmetro formatType, o método de formatação ou de análise passa o tipo de objeto necessário para executar sua operação.In the formatType parameter, the formatting or parsing method passes the type of object it requires to perform its operation. Se a implementação de IFormatProvider puder fornecer essa formatação ou objeto de análise, ele retornará esse objeto.If the IFormatProvider implementation can supply this formatting or parsing object, it returns that object. Caso contrário, ele retornará null.If not, it returns null.

Por exemplo, na chamada para o método Int32.ToString(IFormatProvider), o argumento Method é um objeto IFormatProvider que fornece informações sobre como a representação de cadeia de caracteres da instância de inteiro atual pode ser formatada.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. Quando o tempo de execução executa o método, ele chama o método GetFormat do objeto IFormatProvider e o passa um objeto Type que representa o 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. Se o objeto IFormatProvider puder fornecer um objeto NumberFormatInfo, ele retornará esse objeto.If the IFormatProvider object can supply a NumberFormatInfo object, it returns that object. Se não for possível fornecer um objeto desse tipo, ele retornará null.If it cannot supply an object of that type, it returns null.

Você pode implementar a interface IFormatProvider e o método GetFormat em classes que fornecem formatação personalizada ou serviços de análise.You can implement the IFormatProvider interface and the GetFormat method in classes that provide custom formatting or parsing services. Em seguida, a implementação de IFormatProvider é passada como um argumento para qualquer sobrecarga de um método de análise ou de formatação que tenha um parâmetro do tipo IFormatProvider, como String.Format(IFormatProvider, String, Object[]), Int32.ToString(String, IFormatProvider)ou 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).

Applies to