IFormatProvider.GetFormat(Type) Metoda

Definicja

Zwraca obiekt, który zapewnia usługi formatowania dla określonego typu.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

Parametry

formatType
Type

Obiekt, który określa typ obiektu formatu do zwrócenia.An object that specifies the type of format object to return.

Zwraca

Object

Wystąpienie obiektu określonego przez formatType , jeśli IFormatProvider implementacja może dostarczyć tego typu obiektu; w przeciwnym razie null .An instance of the object specified by formatType, if the IFormatProvider implementation can supply that type of object; otherwise, null.

Przykłady

Poniższy przykład ilustruje użycie klasy implementującej IFormatProvider interfejs i GetFormat metodę.The following example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. AcctNumberFormatKlasa konwertuje Int64 wartość reprezentującą numer konta na sformatowany 12-cyfrowy numer konta.The AcctNumberFormat class converts an Int64 value that represents an account number to a formatted 12-digit account number. Jego GetFormat Metoda zwraca odwołanie do siebie formatType , jeśli parametr odwołuje się do klasy, która implementuje ICustomFormatter ; w przeciwnym razie GetFormat zwraca 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

Wystąpienie AcctNumberFormat klasy można następnie przesłać jako argument do metody, która zapewnia usługi formatowania lub analizy.An instance of the AcctNumberFormat class can then be passed as an argument to a method that provides formatting or parsing services. Na przykład poniższy kod przekazuje AcctNumberFormat klasy do String.Format(IFormatProvider, String, Object[]) metody w celu wygenerowania sformatowanego 12-cyfrowego numeru konta.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.

Uwagi

GetFormat jest metodą wywołania zwrotnego, która pobiera i analizuje metody, aby pobierać informacje o formacie ciągu wejściowego w operacjach analizowania lub formacie ciągu wyjściowego w operacjach formatowania.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. W formatType parametrze Metoda formatowania lub analizowania przekazuje typ obiektu wymaganego do wykonania operacji.In the formatType parameter, the formatting or parsing method passes the type of object it requires to perform its operation. Jeśli IFormatProvider implementacja może dostarczyć ten obiekt formatowania lub analizowania, zwraca ten obiekt.If the IFormatProvider implementation can supply this formatting or parsing object, it returns that object. Jeśli nie, zwraca null .If not, it returns null.

Na przykład w wywołaniu Int32.ToString(IFormatProvider) metody argument metody jest IFormatProvider obiektem, który zawiera informacje na temat sposobu, w jaki ciąg reprezentujący bieżące wystąpienie liczby całkowitej może być sformatowany.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. Gdy środowisko uruchomieniowe wykonuje metodę, wywołuje IFormatProvider GetFormat metodę obiektu i przekazuje go do Type obiektu, który reprezentuje NumberFormatInfo Typ.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. Jeśli IFormatProvider obiekt może dostarczyć NumberFormatInfo obiekt, zwraca ten obiekt.If the IFormatProvider object can supply a NumberFormatInfo object, it returns that object. Jeśli nie można dostarczyć obiektu tego typu, zwraca null .If it cannot supply an object of that type, it returns null.

IFormatProviderInterfejs i metodę można zaimplementować GetFormat w klasach, które zapewniają niestandardowe formatowanie lub usługi analizy.You can implement the IFormatProvider interface and the GetFormat method in classes that provide custom formatting or parsing services. IFormatProviderImplementacja jest następnie przenoszona jako argument do dowolnego przeciążenia metody analizy lub formatowania, która ma parametr typu IFormatProvider , taki jak String.Format(IFormatProvider, String, Object[]) , Int32.ToString(String, IFormatProvider) lub 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).

Dotyczy