IFormatProvider.GetFormat(Type) Methode

Definition

Gibt ein Objekt zurück, das Formatierungsdienste für den angegebenen Typ bereitstellt.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

Parameter

formatType
Type

Ein Objekt, das den Typ des zurückzugebenden Formatierungsobjekts angibt.An object that specifies the type of format object to return.

Gibt zurück

Eine Instanz des von formatType angegebenen Objekts, wenn die IFormatProvider-Implementierung den betreffenden Typ von Objekt angeben kann, andernfalls null.An instance of the object specified by formatType, if the IFormatProvider implementation can supply that type of object; otherwise, null.

Beispiele

Im folgenden Beispiel wird die Verwendung einer Klasse veranschaulicht, die die IFormatProvider -Schnittstelle GetFormat und die-Methode implementiert.The following example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. Die AcctNumberFormat -Klasse konvertiert Int64 einen-Wert, der eine Kontonummer darstellt, in eine formatierte 12-stellige Kontonummer.The AcctNumberFormat class converts an Int64 value that represents an account number to a formatted 12-digit account number. null GetFormat ICustomFormatter formatType Die- MethodegibteinenVerweisaufsichselbstzurück,wennder-ParameteraufeineKlasseverweist,dieimplementiert;andernfallswirdzurückgegeben.GetFormatIts 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

Eine Instanz der AcctNumberFormat -Klasse kann dann als Argument an eine Methode weitergegeben werden, die Formatierungs-oder Analyse-Dienste bereitstellt.An instance of the AcctNumberFormat class can then be passed as an argument to a method that provides formatting or parsing services. Der folgende Code übergibt z. b. AcctNumberFormat eine-Klasse String.Format(IFormatProvider, String, Object[]) an die-Methode, um eine formatierte 12-stellige Kontonummer zu generieren.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.

Hinweise

GetFormatist eine Rückruf Methode, die von Formatierungs-und Methoden Methoden aufgerufen wird, um Informationen über das Format der Eingabe Zeichenfolge in den-oder-Formatierungs Vorgängen oder das Format der Ausgabe Zeichenfolge abzurufen.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. Im- formatType Parameter übergibt die Formatierungs-oder die Methoden Methode den Objekttyp, der zum Ausführen des Vorgangs erforderlich ist.In the formatType parameter, the formatting or parsing method passes the type of object it requires to perform its operation. Wenn die IFormatProvider Implementierung dieses Formatierungs-oder Analyse-Objekt bereitstellen kann, wird dieses Objekt zurückgegeben.If the IFormatProvider implementation can supply this formatting or parsing object, it returns that object. Andernfalls wird zurück nullgegeben.If not, it returns null.

Beispielsweise ist das Methoden Argument beim aufzurufen Int32.ToString(IFormatProvider) der-Methode ein IFormatProvider Objekt, das Informationen darüber bereitstellt, wie die Zeichen folgen Darstellung der aktuellen ganzzahligen Instanz formatiert werden kann.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. Wenn die Laufzeit die-Methode ausführt, ruft Sie IFormatProvider die- GetFormat Methode des-Objekts auf Type und übergibt ihr ein NumberFormatInfo -Objekt, das den-Typ darstellt.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. Wenn das IFormatProvider -Objekt ein NumberFormatInfo -Objekt bereitstellen kann, wird dieses Objekt zurückgegeben.If the IFormatProvider object can supply a NumberFormatInfo object, it returns that object. Wenn kein Objekt dieses Typs bereitgestellt werden kann, wird zurück nullgegeben.If it cannot supply an object of that type, it returns null.

Sie können die IFormatProvider -Schnittstelle und GetFormat die-Methode in Klassen implementieren, die benutzerdefinierte Formatierungs-oder Diagnosedienste bereitstellen.You can implement the IFormatProvider interface and the GetFormat method in classes that provide custom formatting or parsing services. Die IFormatProvider -Implementierung wird dann als Argument an jede Überladung einer Analyse-oder Formatierungs Methode übergeben, die einen Parameter IFormatProvidervom Typ aufweist String.Format(IFormatProvider, String, Object[]), Int32.ToString(String, IFormatProvider)z. DateTime.Parse(String, IFormatProvider)b., oder.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).

Gilt für: