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

次の例は、実装IFormatProviderによって日付と時刻の値の表現を変更する方法を示しています。The following example illustrates how an IFormatProvider implementation can change the representation of a date and time value. この場合、4つの異なるカルチャを表すオブジェクトCultureInfoを使用して、1つの日付が表示されます。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, 16, 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

次の例は、 IFormatProviderインターフェイスGetFormatとメソッドを実装するクラスの使用方法を示しています。The following example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. クラスAcctNumberFormatは、アカウントInt64番号を表す値を、書式設定された12桁の勘定科目番号に変換します。The AcctNumberFormat class converts an Int64 value that represents an account number to a formatted 12-digit account number. パラメーター GetFormatがを実装AcctNumberFormat formatType GetFormat nullするクラスを参照している場合、そのメソッドは現在のインスタンスへの参照を返します。それ以外の場合はを返します。 ICustomFormatterIts 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

を実装IFormatProviderするクラスは、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[])メソッドを呼び出して、書式設定された12桁の勘定科目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

インターフェイスIFormatProviderは、書式設定および解析操作のための書式設定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. 書式設定操作は、型の値をその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ToStringは、型Formatのメソッドと同様です。Typical formatting methods are the ToString methods of a type, as well as Format. 解析操作では、値の文字列形式を、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ParseTryParseとです。Typical parsing methods are Parse and TryParse.

インターフェイスIFormatProviderは、 IFormatProvider.GetFormatという1つのメソッドで構成されます。The IFormatProvider interface consists of a single method, IFormatProvider.GetFormat. GetFormatはコールバックメソッドです。解析メソッドまたは書式指定メソッドは、このメソッドTypeを呼び出し、書式設定または解析メソッドが想定するオブジェクトの型を表すオブジェクトを渡して、書式設定情報を提供します。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. メソッドGetFormatは、その型のオブジェクトを返す役割を担います。The GetFormat method is responsible for returning an object of that type.

IFormatProvider実装は、メソッドを書式設定および解析することによって暗黙的に使用されることがよくあります。IFormatProvider implementations are often used implicitly by formatting and parsing methods. たとえば、メソッドはDateTime.ToString(String) 、システムの現在IFormatProviderのカルチャを表すの実装を暗黙的に使用します。For example, the DateTime.ToString(String) method implicitly uses an IFormatProvider implementation that represents the system's current culture. IFormatProvider実装は、型IFormatProviderのパラメーター ( Int32.Parse(String, IFormatProvider)String.Format(IFormatProvider, String, Object[])など) を持つメソッドによって明示的に指定することもできます。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、数値および日付IFormatProviderと時刻の値の書式設定または解析に使用されるカルチャ固有の情報を提供するために、次の3つの定義済み実装が含まれています。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 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. これには、通常、とIFormatProvider ICustomFormatterの両方を実装する書式指定クラスの作成が含まれます。This typically involves the creation of a formatting class that implements both IFormatProvider and ICustomFormatter. このクラスのインスタンスは、パラメーターとして、カスタム書式設定操作String.Format(IFormatProvider, String, Object[])を実行するメソッドにパラメーターとして渡されます。たとえば、数値を12桁のアカウント番号として書式設定するカスタム実装の例を示します。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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