ICustomFormatter.Format(String, Object, IFormatProvider) Método

  • Referencia

Definición

Espacio de nombres:
System
Ensamblado:
System.Runtime.dll
Ensamblado:
mscorlib.dll
Ensamblado:
netstandard.dll

Convierte el valor del objeto especificado en la representación de cadena equivalente usando el formato y la información de formato específica de la referencia cultural especificados.

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

Parámetros

format
String

Cadena de formato que contiene las especificaciones de formato.

arg
Object

Objeto al que se va a aplicar el formato.

formatProvider
IFormatProvider

Objeto que proporciona información de formato sobre la instancia actual.

Devoluciones

String

Representación de cadena del valor de arg, con el formato que especifican format y formatProvider.

Ejemplos

En el ejemplo siguiente se implementa ICustomFormatter para permitir el formato binario, octal y hexadecimal de valores enteros. Su ICustomFormatter.Format implementación determina si el parámetro de formato es una de las tres cadenas de formato admitidas ("B" para binary, "O" para octal y "H" para hexadecimal) y da formato al arg parámetro correctamente. De lo contrario, si arg no nulles , llama a la arg implementación del IFormattable.ToString parámetro, si existe, o a su método sin ToString parámetros, si no lo hace. Si el valor de arg es null, el método devuelve String.Empty.

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 Después, se puede usar para proporcionar formato personalizado pasando un MyFormatter objeto como parámetro provider del Format método , como se muestra en el ejemplo siguiente.

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)

Comentarios

ICustomFormatter.Format es un método de devolución de llamada. Se llama mediante un método que admite el formato personalizado, como String.Format(IFormatProvider, String, Object[]) o StringBuilder.AppendFormat(IFormatProvider, String, Object[]). Se llama a la implementación una vez para cada elemento de formato en una cadena de formato compuesto. Por ejemplo, en la siguiente instrucción, el ICustomFormatter.Format método se llama tres veces.

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))

El arg parámetro es el objeto de la lista de objetos cuya posición de base cero corresponde al índice de un elemento de formato determinado.

El format parámetro contiene una cadena de formato, que es el formatString componente de un elemento de formato. Si el elemento de formato no tiene ningún formatString componente, el valor de format es null. Si format es null, dependiendo del tipo de arg, es posible que pueda usar la especificación de formato predeterminada de su elección.

El formatProvider parámetro es la IFormatProvider implementación que proporciona formato para arg. Normalmente, es una instancia de la ICustomFormatter implementación. Si formatProvider es null, omita ese parámetro.

La implementación del Format método debe incluir la siguiente funcionalidad para que .NET Framework pueda proporcionar formato que no admita. Si el método de formato no admite un formato, determine si el objeto al que se va a dar formato implementa la IFormattable interfaz . Si es así, invoque el IFormattable.ToString método de esa interfaz. De lo contrario, invoque el método predeterminado Object.ToString del objeto subyacente. En el código siguiente se muestra este patrón.

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()

Se aplica a

Consulte también