IFormatProvider IFormatProvider IFormatProvider IFormatProvider Interface

定義

書式設定を制御するオブジェクトを取得するためのメカニズムを定義します。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
派生
属性

次の例を示して 方法、IFormatProvider実装は、日付と時刻の値の表現を変更できます。The following example illustrates how an IFormatProvider implementation can change the representation of a date and time value. 使用して 1 つの日付を表示するこの例では、 CultureInfo 4 つの異なるカルチャを表すオブジェクト。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, 4, 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

次の例では、実装するクラスの使用、IFormatProviderインターフェイスとGetFormatメソッド。The following example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. AcctNumberFormatクラスに変換するInt6412 桁の書式設定されたアカウント番号への勘定科目番号を表す値。The AcctNumberFormat class converts an Int64 value that represents an account number to a formatted 12-digit account number. そのGetFormatメソッドは、現在への参照を返しますAcctNumberFormatインスタンスの場合、formatTypeパラメーターを実装するクラスを指しますICustomFormatter、それ以外のGetFormat返しますnullIts 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

実装するクラスIFormatProviderし、書式設定および解析操作の呼び出しで使用できます。The class that implements IFormatProvider can then be used in a call to a formatting and parsing operation. たとえば、次のコードは、 String.Format(IFormatProvider, String, Object[]) 12 桁の書式設定されたアカウント番号を含む文字列を生成します。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.

注釈

IFormatProviderインターフェイスは、書式設定して、解析操作の書式情報を提供するオブジェクトを提供します。The IFormatProvider interface supplies an object that provides formatting information for formatting and parsing operations. 書式設定操作では、型の値を値の文字列形式に変換します。Formatting operations convert the value of a type to the string representation of that value. 一般的な書式指定メソッドは、 ToString 、型のメソッドだけでなくFormatします。Typical formatting methods are the ToString methods of a type, as well as Format. 解析操作では、値の文字列表現をその値を持つ型に変換します。Parsing operations convert the string representation of a value to a type with that value. 一般的な解析メソッドはParseTryParseします。Typical parsing methods are Parse and TryParse.

IFormatProviderインターフェイスは、1 つのメソッドで構成されますIFormatProvider.GetFormatします。The IFormatProvider interface consists of a single method, IFormatProvider.GetFormat. GetFormat コールバック メソッドです。 解析または書式指定メソッド呼び出しを渡します、 Type 、書式設定またはメソッドの解析が必要とするオブジェクトの型を表すオブジェクトを書式設定の情報が提供されます。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. GetFormatメソッドがその型のオブジェクトが返されます。The GetFormat method is responsible for returning an object of that type.

IFormatProvider 書式設定と解析メソッドで実装が暗黙的に使用されます。IFormatProvider implementations are often used implicitly by formatting and parsing methods. たとえば、DateTime.ToString(String)メソッドは暗黙的に使用、IFormatProviderシステムの現在のカルチャを表す実装します。For example, the DateTime.ToString(String) method implicitly uses an IFormatProvider implementation that represents the system's current culture. IFormatProvider 実装が型のパラメーターがメソッドによって明示的に指定することもできますIFormatProviderなどInt32.Parse(String, IFormatProvider)String.Format(IFormatProvider, String, Object[])します。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[]).

.NET Framework には、定義済みの次の 3 つが含まれています。IFormatProvider書式設定または解析の数値および日付と時刻の値で使用されるカルチャ固有の情報を提供する実装。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:

.NET Framework では、カスタム書式設定もサポートしています。The .NET Framework also supports custom formatting. 通常、両方を実装するクラスを書式設定の作成IFormatProviderICustomFormatterします。This typically involves the creation of a formatting class that implements both IFormatProvider and ICustomFormatter. など、カスタムの書式設定操作を実行するメソッドにパラメーターとしてこのクラスのインスタンスが、渡されるString.Format(IFormatProvider, String, Object[])12 桁のアカウント番号としての数値の書式設定、このようなカスタム実装を示しています。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.

メソッド

GetFormat(Type) GetFormat(Type) GetFormat(Type) GetFormat(Type)

指定した型の書式指定サービスを提供するオブジェクトを返します。Returns an object that provides formatting services for the specified type.

適用対象

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