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。

public:
 System::Object ^ GetFormat(Type ^ formatType);
public 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。

戻り値

Object

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 null

次の例は、インターフェイスとメソッドを実装するクラスの使用をIFormatProviderGetFormat示しています。 このクラスは AcctNumberFormat 、アカウント番号を Int64 表す値を書式設定された 12 桁のアカウント番号に変換します。 そのメソッドはGetFormat、パラメーターが実装ICustomFormatterするクラスを参照している場合formatTypeはそれ自体への参照を返nullします。それ以外の場合は、 GetFormat .

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;
   }
}
open System
open System.Globalization

type AcctNumberFormat() =
    let [<Literal>] ACCT_LENGTH = 12

    interface IFormatProvider with
        member this.GetFormat(formatType: Type) =
            if formatType = typeof<ICustomFormatter> then
                this
            else
                null

    interface ICustomFormatter with
        member this.Format(fmt: string, arg: obj, formatProvider: IFormatProvider) =
            // Provide default formatting if arg is not an Int64.
            // Provide default formatting for unsupported format strings.
            let ufmt = fmt.ToUpper CultureInfo.InvariantCulture
            if arg.GetType() = typeof<Int64> && (ufmt = "H" || ufmt = "I") then
                // Convert argument to a string.
                let result = string arg

                let result =
                    // If account number is less than 12 characters, pad with leading zeroes.
                    if result.Length < ACCT_LENGTH then
                        result.PadLeft(ACCT_LENGTH, '0')
                    else result
                
                let result =
                    // If account number is more than 12 characters, truncate to 12 characters.
                    if result.Length > ACCT_LENGTH then
                        result.Substring(0, ACCT_LENGTH)
                    else result

                // Integer-only format.
                if ufmt = "I" then 
                    result
                // Add hyphens for H format specifier.
                else // Hyphenated format.
                    result.Substring(0, 5) + "-" + result.Substring(5, 3) + "-" + result.Substring(8)
            else
                try
                    this.HandleOtherFormats(fmt, arg)
                with :? FormatException as e ->
                    raise (FormatException($"The format of '{fmt}' is invalid.", e))
            
    member _.HandleOtherFormats(format: string, arg: obj) =
        match arg with
        | :? IFormattable as arg ->
            arg.ToString(format, CultureInfo.CurrentCulture)
        | null -> 
            string arg
        | _ -> 
            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、クラスの AcctNumberFormat インスタンスを、書式設定または解析サービスを提供するメソッドに引数として渡すことができます。 たとえば、次のコードは、書式設定された 12 桁のString.Format(IFormatProvider, String, Object[])アカウント番号を生成するクラスをメソッドに渡AcctNumberFormatします。

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.
open System
open System.Globalization

type DaysOfWeek = Monday = 1 | Tuesday = 2

[<EntryPoint>]
let main _ =
    let acctNumber = 104254567890L
    let balance = 16.34
    let wday = DaysOfWeek.Monday

    let output = 
        String.Format(AcctNumberFormat(), 
                      "On {2}, the balance of account {0:H} was {1:C2}.", 
                      acctNumber, balance, wday)
    printfn $"{output}"

    let wday = DaysOfWeek.Tuesday
    let output = 
        String.Format(AcctNumberFormat(),
                      "On {2}, the balance of account {0:I} was {1:C2}.",
                      acctNumber, balance, wday)
    printfn $"{output}"
    0

// 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が呼び出して、解析操作での入力文字列の形式または書式設定操作での出力文字列の形式に関する情報を取得するコールバック メソッドです。 formatTypeパラメーターでは、書式設定メソッドまたは解析メソッドは、その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。 実装で IFormatProvider この書式設定または解析オブジェクトを指定できる場合は、そのオブジェクトを返します。 そうでない場合は、 null.

たとえば、メソッドの Int32.ToString(IFormatProvider) 呼び出しでは、メソッド引数は IFormatProvider 、現在の整数インスタンスの文字列表現の書式設定方法に関する情報を提供するオブジェクトです。 ランタイムは、メソッドを実行すると、オブジェクトのメソッドをIFormatProvider呼び出し、型をType表すオブジェクトをNumberFormatInfoGetFormatします。 オブジェクトがオブジェクトをIFormatProviderNumberFormatInfo指定できる場合は、そのオブジェクトを返します。 その型のオブジェクトを指定できない場合は、返されます null

インターフェイスとメソッドはIFormatProviderGetFormat、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に実装できます。 IFormatProviderその後、実装は、型のパラメーターIFormatProviderを持つ解析メソッドまたは書式設定メソッドのオーバーロードに引数として渡されます (例: String.Format(IFormatProvider, String, Object[]),Int32.ToString(String, IFormatProvider)、、 DateTime.Parse(String, IFormatProvider).

適用対象