ICustomFormatter.Format(String, Object, IFormatProvider) Metoda

Definicja

Przestrzeń nazw:

System

Zestaw:

System.Runtime.dll

Konwertuje wartość określonego obiektu na równoważną reprezentację ciągu przy użyciu określonego formatu i informacji o formatowaniu specyficznym dla kultury.

public:
 System::String ^ Format(System::String ^ format, System::Object ^ arg, IFormatProvider ^ formatProvider);

public string Format (string? format, object? arg, IFormatProvider? formatProvider);

abstract member Format : string * obj * IFormatProvider -> string

Public Function Format (format As String, arg As Object, formatProvider As IFormatProvider) As String

Parametry

format

String

Ciąg formatu zawierający specyfikacje formatowania.

arg

Object

Obiekt do sformatowania.

formatProvider

IFormatProvider

Obiekt, który dostarcza informacje o formacie bieżącego wystąpienia.

Zwraca

String

Ciąg reprezentujący wartość arg, sformatowaną zgodnie z parametrami format i formatProvider.

Przykłady

Poniższy przykład implementuje ICustomFormatter , aby umożliwić formatowanie binarne, ósemkowe i szesnastkowe wartości całkowitych. Jego ICustomFormatter.Format implementacja określa, czy parametr formatu jest jednym z trzech obsługiwanych ciągów formatu ("B" dla danych binarnych, "O" dla ósemki i "H" dla szesnastkowej) i formatuje arg parametr odpowiednio. W przeciwnym razie, jeśli arg nie null, wywołuje implementację parametru IFormattable.ToStringarg, jeśli taki istnieje lub jego metoda bez ToString parametrów, jeśli nie. Jeśli arg parametr ma nullwartość , metoda zwraca String.Emptywartość .

using System;
using System.Globalization;
using System.Numerics;

public class MyFormatter : IFormatProvider, ICustomFormatter
{
    // IFormatProvider.GetFormat implementation.
    public object GetFormat(Type formatType)
    {
        // Determine whether custom formatting object is requested.
        if (formatType == typeof(ICustomFormatter))
            return this;
        else
            return null;
    }

    // Format number in binary (B), octal (O), or hexadecimal (H).
    public string Format(string format, object arg, IFormatProvider formatProvider)
    {
        // Handle format string.
        int baseNumber;
        // Handle null or empty format string, string with precision specifier.
        string thisFmt = String.Empty;
        // Extract first character of format string (precision specifiers
        // are not supported).
        if (!String.IsNullOrEmpty(format))
            thisFmt = format.Length > 1 ? format.Substring(0, 1) : format;

        // Get a byte array representing the numeric value.
        byte[] bytes;
        if (arg is sbyte)
        {
            string byteString = ((sbyte)arg).ToString("X2");
            bytes = new byte[1] { Byte.Parse(byteString, System.Globalization.NumberStyles.HexNumber) };
        }
        else if (arg is byte)
        {
            bytes = new byte[1] { (byte)arg };
        }
        else if (arg is short)
        {
            bytes = BitConverter.GetBytes((short)arg);
        }
        else if (arg is int)
        {
            bytes = BitConverter.GetBytes((int)arg);
        }
        else if (arg is long)
        {
            bytes = BitConverter.GetBytes((long)arg);
        }
        else if (arg is ushort)
        {
            bytes = BitConverter.GetBytes((ushort)arg);
        }
        else if (arg is uint)
        {
            bytes = BitConverter.GetBytes((uint)arg);
        }
        else if (arg is ulong)
        {
            bytes = BitConverter.GetBytes((ulong)arg);
        }
        else if (arg is BigInteger)
        {
            bytes = ((BigInteger)arg).ToByteArray();
        }
        else
        {
            try
            {
                return HandleOtherFormats(format, arg);
            }
            catch (FormatException e)
            {
                throw new FormatException(String.Format("The format of '{0}' is invalid.", format), e);
            }
        }

        switch (thisFmt.ToUpper())
        {
            // Binary formatting.
            case "B":
                baseNumber = 2;
                break;
            case "O":
                baseNumber = 8;
                break;
            case "H":
                baseNumber = 16;
                break;
            // Handle unsupported format strings.
            default:
                try
                {
                    return HandleOtherFormats(format, arg);
                }
                catch (FormatException e)
                {
                    throw new FormatException(String.Format("The format of '{0}' is invalid.", format), e);
                }
        }

        // Return a formatted string.
        string numericString = String.Empty;
        for (int ctr = bytes.GetUpperBound(0); ctr >= bytes.GetLowerBound(0); ctr--)
        {
            string byteString = Convert.ToString(bytes[ctr], baseNumber);
            if (baseNumber == 2)
                byteString = new String('0', 8 - byteString.Length) + byteString;
            else if (baseNumber == 8)
                byteString = new String('0', 4 - byteString.Length) + byteString;
            // Base is 16.
            else
                byteString = new String('0', 2 - byteString.Length) + byteString;

            numericString += byteString + " ";
        }
        return numericString.Trim();
    }

    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
open System.Numerics

type MyFormatter() =
    interface IFormatProvider with
        // IFormatProvider.GetFormat implementation.
        member this.GetFormat(formatType: Type) =
            // Determine whether custom formatting object is requested.
            if formatType = typeof<ICustomFormatter> then
                this
            else
                null

    interface ICustomFormatter with
        // Format number in binary (B), octal (O), or hexadecimal (H).
        member this.Format(format, arg: obj, formatProvider: IFormatProvider) =
            // Handle null or empty format string, string with precision specifier.
            let thisFmt =
                // Extract first character of format string (precision specifiers
                // are not supported).
                if String.IsNullOrEmpty format |> not then
                    if format.Length > 1 then 
                        format.Substring(0, 1) 
                    else 
                        format
                else
                    String.Empty

            // Get a byte array representing the numeric value.
            let bytes =
                match arg with
                | :? sbyte as arg ->
                    let byteString = arg.ToString "X2"
                    Some [| Byte.Parse(byteString, NumberStyles.HexNumber) |]
                | :? byte as arg ->
                    Some [| arg |]
                | :? int16 as arg ->
                    BitConverter.GetBytes arg
                    |> Some
                | :? int as arg ->
                    BitConverter.GetBytes arg
                    |> Some
                | :? int64 as arg ->
                    BitConverter.GetBytes arg
                    |> Some
                | :? uint16 as arg ->
                    BitConverter.GetBytes arg
                    |> Some
                | :? uint as arg ->
                    BitConverter.GetBytes arg
                    |> Some
                | :? uint64 as arg ->
                    BitConverter.GetBytes arg
                    |> Some
                | :? bigint as arg ->
                    arg.ToByteArray()
                    |> Some
                | _ ->
                    None
            let baseNumber =
                match thisFmt.ToUpper() with
                    // Binary formatting.
                    | "B" -> Some 2
                    | "O" -> Some 8
                    | "H" -> Some 16
                    // Handle unsupported format strings.
                    | _ -> None

            match bytes, baseNumber with
            | Some bytes, Some baseNumber ->
                // Return a formatted string.
                let mutable numericString = String.Empty
                for i = bytes.GetUpperBound 0 to bytes.GetLowerBound 0 do
                    let byteString = Convert.ToString(bytes[i], baseNumber)
                    let byteString =
                        match baseNumber with
                        | 2 ->
                            String('0', 8 - byteString.Length) + byteString
                        | 8 ->
                            String('0', 4 - byteString.Length) + byteString
                        // Base is 16.
                        | _ ->
                            String('0', 2 - byteString.Length) + byteString
                    numericString <- numericString + byteString + " "
                numericString.Trim()
            | _ ->
                try
                    this.HandleOtherFormats(format, arg)
                with :? FormatException as e ->
                    raise (FormatException($"The format of '{format}' is invalid.", e))
                    
    member private this.HandleOtherFormats(format, arg: obj) =
        match arg with
        | :? IFormattable as arg ->
            arg.ToString(format, CultureInfo.CurrentCulture)
        | null ->
            String.Empty
        | _ ->
            string arg

Imports System.Globalization
Imports System.Numerics

Public Class MyFormatter : Implements IFormatProvider, ICustomFormatter
   ' IFormatProvider.GetFormat implementation.
   Public Function GetFormat(formatType As Type) As Object _
                   Implements IFormatProvider.GetFormat
      ' Determine whether custom formatting object is requested.
      If formatType Is GetType(ICustomFormatter) Then
         Return Me
      Else
         Return Nothing
      End If
   End Function   

   ' Format number in binary (B), octal (O), or hexadecimal (H).
   Public Function Format(fmt As String, arg As Object, _
                          formatProvider As IFormatProvider) As String _
                   Implements ICustomFormatter.Format

     ' Handle format string.
      Dim base As Integer
      ' Handle null or empty format string, string with precision specifier.
      Dim thisFmt As String = String.Empty
      ' Extract first character of format string (precision specifiers
      ' are not supported by MyFormatter).
      If Not String.IsNullOrEmpty(fmt) Then
         thisFmt = CStr(IIf(fmt.Length > 1, fmt.Substring(0, 1), fmt))
      End If
         


      ' Get a byte array representing the numeric value.
      Dim bytes() As Byte
      If TypeOf(arg) Is SByte Then
         Dim byteString As String = CType(arg, SByte).ToString("X2")
         bytes = New Byte(0) { Byte.Parse(byteString, System.Globalization.NumberStyles.HexNumber ) }
      ElseIf TypeOf(arg) Is Byte Then
         bytes = New Byte(0) { CType(arg, Byte) }
      ElseIf TypeOf(arg) Is Int16 Then
         bytes = BitConverter.GetBytes(CType(arg, Int16))
      ElseIf TypeOf(arg) Is Int32 Then
         bytes = BitConverter.GetBytes(CType(arg, Int32))
      ElseIf TypeOf(arg) Is Int64 Then
         bytes = BitConverter.GetBytes(CType(arg, Int64))
      ElseIf TypeOf(arg) Is UInt16 Then
         bytes = BitConverter.GetBytes(CType(arg, UInt16))
      ElseIf TypeOf(arg) Is UInt32 Then
         bytes = BitConverter.GetBytes(CType(arg, UInt64))
      ElseIf TypeOf(arg) Is UInt64 Then
         bytes = BitConverter.GetBytes(CType(arg, UInt64))                  
      ElseIf TypeOf(arg) Is BigInteger Then
         bytes = CType(arg, BigInteger).ToByteArray()
      Else
         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

      Select Case thisFmt.ToUpper()
         ' Binary formatting.
         Case "B"
            base = 2        
         Case "O"
            base = 8
         Case "H"
            base = 16
         ' Handle unsupported format strings.
         Case Else
            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 Select
      
      ' Return a formatted string.
      Dim numericString As String = String.Empty
      For ctr As Integer = bytes.GetUpperBound(0) To bytes.GetLowerBound(0) Step -1
         Dim byteString As String = Convert.ToString(bytes(ctr), base)
         If base = 2 Then
            byteString = New String("0"c, 8 - byteString.Length) + byteString
         ElseIf base = 8 Then
            byteString = New String("0"c, 4 - byteString.Length) + byteString
         ' Base is 16.
         Else     
            byteString = New String("0"c, 2 - byteString.Length) + byteString
         End If
         numericString +=  byteString + " "
      Next
      Return numericString.Trim()
   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

MyFormatter Następnie można użyć do zapewnienia formatowania niestandardowego, przekazując MyFormatter obiekt jako provider parametr Format metody, jak pokazano w poniższym przykładzie.

public class Example
{
    public static void Main()
    {
        Console.WindowWidth = 100;

        byte byteValue = 124;
        Console.WriteLine(String.Format(new MyFormatter(),
                                        "{0} (binary: {0:B}) (hex: {0:H})", byteValue));

        int intValue = 23045;
        Console.WriteLine(String.Format(new MyFormatter(),
                                        "{0} (binary: {0:B}) (hex: {0:H})", intValue));

        ulong ulngValue = 31906574882;
        Console.WriteLine(String.Format(new MyFormatter(),
                                        "{0}\n   (binary: {0:B})\n   (hex: {0:H})",
                                        ulngValue));

        BigInteger bigIntValue = BigInteger.Multiply(Int64.MaxValue, 2);
        Console.WriteLine(String.Format(new MyFormatter(),
                                        "{0}\n   (binary: {0:B})\n   (hex: {0:H})",
                                        bigIntValue));
    }
}
// The example displays the following output:
//    124 (binary: 01111100) (hex: 7c)
//    23045 (binary: 00000000 00000000 01011010 00000101) (hex: 00 00 5a 05)
//    31906574882
//       (binary: 00000000 00000000 00000000 00000111 01101101 11000111 10110010 00100010)
//       (hex: 00 00 00 07 6d c7 b2 22)
//    18446744073709551614
//       (binary: 00000000 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111110)
//       (hex: 00 ff ff ff ff ff ff ff fe)

Console.WindowWidth <- 100

let byteValue = 124uy
String.Format(MyFormatter(), "{0} (binary: {0:B}) (hex: {0:H})", byteValue)
|> printfn "%s"

let intValue = 23045
String.Format(MyFormatter(), "{0} (binary: {0:B}) (hex: {0:H})", intValue)
|> printfn "%s"

let ulngValue = 31906574882uL
String.Format(MyFormatter(), "{0}\n   (binary: {0:B})\n   (hex: {0:H})", ulngValue)
|> printfn "%s"

let bigIntValue = BigInteger.Multiply(Int64.MaxValue, 2)
String.Format(MyFormatter(), "{0}\n   (binary: {0:B})\n   (hex: {0:H})", bigIntValue)
|> printfn "%s"

// The example displays the following output:
//    124 (binary: 01111100) (hex: 7c)
//    23045 (binary: 00000000 00000000 01011010 00000101) (hex: 00 00 5a 05)
//    31906574882
//       (binary: 00000000 00000000 00000000 00000111 01101101 11000111 10110010 00100010)
//       (hex: 00 00 00 07 6d c7 b2 22)
//    18446744073709551614
//       (binary: 00000000 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111110)
//       (hex: 00 ff ff ff ff ff ff ff fe)

Public Module Example
   Public Sub Main
      Console.WindowWidth = 100
      
      Dim byteValue As Byte = 124
      Console.WriteLine(String.Format(New MyFormatter(), _
                                      "{0} (binary: {0:B}) (hex: {0:H})", byteValue))
      
      Dim intValue As Integer = 23045
      Console.WriteLine(String.Format(New MyFormatter(), _
                                      "{0} (binary: {0:B}) (hex: {0:H})", intValue))
      
      Dim ulngValue As ULong = 31906574882
      Console.WriteLine(String.Format(New MyFormatter(), _
                                      "{0} {1}   (binary: {0:B}) {1}   (hex: {0:H})", _
                                      ulngValue, vbCrLf))

      Dim bigIntValue As BigInteger = BigInteger.Multiply(Int64.MaxValue, 2)
      Console.WriteLine(String.Format(New MyFormatter(), _
                                      "{0} {1}   (binary: {0:B}) {1}   (hex: {0:H})", _
                                      bigIntValue, vbCrLf))
   End Sub
End Module
' The example displays the following output:
'    124 (binary: 01111100) (hex: 7c)
'    23045 (binary: 00000000 00000000 01011010 00000101) (hex: 00 00 5a 05)
'    31906574882
'       (binary: 00000000 00000000 00000000 00000111 01101101 11000111 10110010 00100010)
'       (hex: 00 00 00 07 6d c7 b2 22)
'    18446744073709551614
'       (binary: 00000000 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111110)
'       (hex: 00 ff ff ff ff ff ff ff fe)

Uwagi

ICustomFormatter.Format jest metodą wywołania zwrotnego. Jest wywoływana przez metodę, która obsługuje formatowanie niestandardowe, takie jak String.Format(IFormatProvider, String, Object[]) lub StringBuilder.AppendFormat(IFormatProvider, String, Object[]). Implementacja jest wywoływana raz dla każdego elementu formatu w ciągu formatu złożonego. Na przykład w poniższej instrukcji metoda jest wywoływana ICustomFormatter.Format trzy razy.

Console.WriteLine(String.Format(new MyFormatter(),
                                "{0} (binary: {0:B}) (hex: {0:H})", byteValue));

String.Format(MyFormatter(), "{0} (binary: {0:B}) (hex: {0:H})", byteValue)
|> printfn "%s"

Console.WriteLine(String.Format(New MyFormatter(), _
                                "{0} (binary: {0:B}) (hex: {0:H})", byteValue))

Parametr arg jest obiektem na liście obiektów, którego położenie na podstawie zera odpowiada indeksowi określonego elementu formatu.

Parametr format zawiera ciąg formatu, który jest formatString składnikiem elementu formatu. Jeśli element formatu nie formatString ma składnika, wartość to formatnull. Jeśli format parametr ma nullwartość , w zależności od typu arg, możesz użyć wybranej domyślnej specyfikacji formatu.

Parametr formatProvider jest implementacjąIFormatProvider, która zapewnia formatowanie dla .arg Zazwyczaj jest to wystąpienie implementacji ICustomFormatter . Jeśli formatProvider parametr ma nullwartość , zignoruj ten parametr.

Implementacja Format metody musi zawierać następujące funkcje, dzięki czemu .NET Framework może zapewnić formatowanie, które nie jest obsługiwane. Jeśli metoda formatowania nie obsługuje formatu, określ, czy obiekt sformatowany implementuje IFormattable interfejs. Jeśli tak, wywołaj metodę IFormattable.ToString tego interfejsu. W przeciwnym razie wywołaj domyślną Object.ToString metodę obiektu bazowego. Poniższy kod ilustruje ten wzorzec.

if (arg is IFormattable)
    return ((IFormattable)arg).ToString(format, CultureInfo.CurrentCulture);
else if (arg != null)
    return arg.ToString();

match arg with
| :? IFormattable as arg ->
    arg.ToString(format, CultureInfo.CurrentCulture)
| null ->
    String.Empty
| _ ->
    string arg

If TypeOf arg Is IFormattable Then
   Return DirectCast(arg, IFormattable).ToString(fmt, CultureInfo.CurrentCulture)
ElseIf arg IsNot Nothing Then
   Return arg.ToString()

Zobacz też

• IFormattable
• Typy formatowania na platformie .NET
• Formatowanie złożone