IFormatProvider.GetFormat(Type) メソッド

定義

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.

public:
 System::Object ^ GetFormat(Type ^ formatType);
public object GetFormat (Type formatType);
abstract member GetFormat : Type -> obj
Public Function GetFormat (formatType As Type) As Object

パラメーター

formatType
Type

返す書式オブジェクトの型を指定するオブジェクト。An object that specifies the type of format object to return.

戻り値

IFormatProvider の実装が formatType で指定された型のオブジェクトを提供できる場合は、そのオブジェクトのインスタンス。それ以外の場合は nullAn instance of the object specified by formatType, if the IFormatProvider implementation can supply that type of object; otherwise, null.

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GetFormat formatType ICustomFormatterするクラスを参照している場合、そのメソッドは自身への参照nullを返します。それ以外の場合はを返します。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

その後、 AcctNumberFormatクラスのインスタンスを引数として、書式設定または解析サービスを提供するメソッドに渡すことができます。An instance of the AcctNumberFormat class can then be passed as an argument to a method that provides formatting or parsing services. たとえば、次のコードは、 AcctNumberFormatクラスをString.Format(IFormatProvider, String, Object[])メソッドに渡して、書式設定された12桁の勘定科目番号を生成します。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.

注釈

GetFormatは、書式設定および解析メソッドを呼び出して、解析操作の入力文字列の形式に関する情報を取得したり、書式設定操作で出力文字列の形式に関する情報を取得したりするコールバックメソッドです。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. formatTypeパラメーターでは、書式設定または解析メソッドは、操作を実行するために必要なオブジェクトの型を渡します。In the formatType parameter, the formatting or parsing method passes the type of object it requires to perform its operation. 実装がIFormatProviderこの書式設定または解析オブジェクトを提供できる場合は、そのオブジェクトが返されます。If the IFormatProvider implementation can supply this formatting or parsing object, it returns that object. そうでない場合はnull、を返します。If not, it returns null.

たとえば、メソッドのInt32.ToString(IFormatProvider)呼び出しでIFormatProviderは、メソッドの引数は、現在の整数インスタンスの文字列形式がどのように書式設定されるかについての情報を提供するオブジェクトです。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. ランタイムは、メソッドを実行IFormatProviderすると、オブジェクトのGetFormatメソッドを呼び出し、 NumberFormatInfo型をType表すオブジェクトを渡します。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. オブジェクトがオブジェクトをNumberFormatInfo提供できる場合は、そのオブジェクトを返します。 IFormatProviderIf the IFormatProvider object can supply a NumberFormatInfo object, it returns that object. その型のオブジェクトを指定できない場合は、をnull返します。If it cannot supply an object of that type, it returns null.

IFormatProvider インターフェイスGetFormatとメソッドは、カスタムの書式設定または解析サービスを提供するクラスで実装できます。You can implement the IFormatProvider interface and the GetFormat method in classes that provide custom formatting or parsing services. IFormatProvider実装はString.Format(IFormatProvider, String, Object[])、 、Int32.ToString(String, IFormatProvider)、など、型のパラメーターを持つ解析または書式指定メソッドのオーバーロードに引数として渡されます。DateTime.Parse(String, IFormatProvider) IFormatProviderThe 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).

適用対象