Stringhe di formato numerico standard

Le stringhe di formato numerico standard vengono utilizzate per formattare tipi numerici comuni. Una stringa di formato numerico standard utilizza il formato Axx, dove A è un carattere alfabetico denominato identificatore di formato e xx è un valore integer facoltativo denominato identificatore di precisione. L'identificatore di precisione, compreso tra 0 e 99, controlla il numero di cifre nel risultato. Le stringhe di formato numerico contenenti più caratteri alfabetici, inclusi gli spazi, vengono interpretate come stringhe di formato numerico personalizzato.

Nella tabella riportata di seguito vengono descritti gli identificatori di formato numerico standard. Per gli esempi dell'output prodotto da ogni identificatore di formato, vedere Esempi di output di stringhe di formato numerico standard. Per ulteriori informazioni, vedere le note che seguono la tabella.

Note

Impostazioni del Pannello di controllo

Le impostazioni di Opzioni internazionali e della lingua nel Pannello di controllo influiscono sulla stringa risultato prodotta da un'operazione di formattazione. Queste impostazioni vengono utilizzate per inizializzare l'oggetto NumberFormatInfo associato alla lingua del thread corrente, che fornisce i valori utilizzati per definire la formattazione. Computer con impostazioni diverse generano stringhe di risultati diverse.

Proprietà NumberFormatInfo

La formattazione è influenzata dalle proprietà dell'oggetto NumberFormatInfo corrente, che viene fornito in modo implicito dalla lingua del thread corrente o in modo esplicito dal parametro IFormatProvider del metodo che richiama la formattazione. Specificare un oggetto NumberFormatInfo o CultureInfo per questo parametro.

Tipi numerici integrali e a virgola mobile

Alcune descrizioni di identificatori di formato numerico standard fanno riferimento a tipi numerici integrali o a virgola mobile. I tipi numerici integrali sono Byte, SByte, Int16, Int32, Int64, UInt16, UInt32 e UInt64. I tipi numerici a virgola mobile sono Decimal, Single e Double.

Valori infiniti a virgola mobile e NaN

Indipendentemente dalla stringa di formato, se il valore di un tipo a virgola mobile Single o Double è un numero infinito positivo, un numero infinito negativo o un valore NaN (Not a Number, non numero), la stringa formattata corrisponderà al valore della proprietà PositiveInfinitySymbol, NegativeInfinitySymbol o NaNSymbol corrispondente specificata dall'oggetto NumberFormatInfo attualmente applicabile.

Esempio

Nell'esempio di codice riportato di seguito viene formattato un valore numerico integrale a virgola mobile utilizzando la lingua corrente del thread, una lingua specificata e tutti gli identificatori di formato numerico standard. In questo esempio di codice vengono utilizzati due particolari tipi numerici, ma verrebbero prodotti risultati simili per qualsiasi tipo di base numerico (Byte, SByte, Int16, Int32, Int64, UInt16, UInt32, UInt64, Decimal, Single e Double).

' This code example demonstrates the ToString(String) and 
' ToString(String, IFormatProvider) methods for integral and
' floating-point numbers, in conjunction with the standard 
' numeric format specifiers.
' This code example uses the System.Int32 integral type and 
' the System.Double floating-point type, but would yield 
' similar results for any of the numeric types. The integral 
' numeric types are System.Byte, SByte, Int16, Int32, Int64, 
' UInt16, UInt32, and UInt64. The floating-point numeric types 
' are Decimal, Single, and Double.

Imports System
Imports System.Globalization
Imports System.Threading

Class Sample
    Public Shared Sub Main() 
        ' Format a negative integer or floating-point number in various ways.
        Dim integralVal As Integer = -12345
        Dim floatingVal As Double  = -1234.567
        
        Dim msgCurrency As String =    "(C) Currency: . . . . . . "
        Dim msgDecimal As String =     "(D) Decimal:. . . . . . . "
        Dim msgScientific As String =  "(E) Scientific: . . . . . "
        Dim msgFixedPoint As String =  "(F) Fixed point:. . . . . "
        Dim msgGeneral As String =     "(G) General (default):. . "
        Dim msgNumber As String =      "(N) Number: . . . . . . . "
        Dim msgPercent As String =     "(P) Percent:. . . . . . . "
        Dim msgRoundTrip As String =   "(R) Round-trip: . . . . . "
        Dim msgHexadecimal As String = "(X) Hexadecimal:. . . . . "
        
        Dim msg1 As String = "Use ToString(String) and the current thread culture." + vbLf
        Dim msg2 As String = "Use ToString(String, IFormatProvider) and a specified culture." + vbLf
        Dim msgCulture As String = "Culture:"
        Dim msgIntegralVal As String = "Integral value:"
        Dim msgFloatingVal As String = "Floating-point value:"
        
        Dim ci As CultureInfo
        '
        Console.Clear()
        Console.WriteLine("Standard Numeric Format Specifiers:" & vbLf)
        ' Display the values.
        Console.WriteLine(msg1)
        
        ' Display the thread current culture, which is used to format the values.
        ci = Thread.CurrentThread.CurrentCulture
        Console.WriteLine("{0,-26}{1}", msgCulture, ci.DisplayName)
        
        ' Display the integral and floating-point values.
        Console.WriteLine("{0,-26}{1}", msgIntegralVal, integralVal)
        Console.WriteLine("{0,-26}{1}", msgFloatingVal, floatingVal)
        Console.WriteLine()
        
        ' Use the format specifiers that are only for integral types.
        Console.WriteLine("Format specifiers only for integral types:")
        Console.WriteLine(msgDecimal     & integralVal.ToString("D"))
        Console.WriteLine(msgHexadecimal & integralVal.ToString("X"))
        Console.WriteLine()
        
        ' Use the format specifier that is only for the Single and Double 
        ' floating-point types.
        Console.WriteLine("Format specifier only for the Single and Double types:")
        Console.WriteLine(msgRoundTrip   & floatingVal.ToString("R"))
        Console.WriteLine()
        
        ' Use the format specifiers that are for integral or floating-point types.
        Console.WriteLine("Format specifiers for integral or floating-point types:")
        Console.WriteLine(msgCurrency    & floatingVal.ToString("C"))
        Console.WriteLine(msgScientific  & floatingVal.ToString("E"))
        Console.WriteLine(msgFixedPoint  & floatingVal.ToString("F"))
        Console.WriteLine(msgGeneral     & floatingVal.ToString("G"))
        Console.WriteLine(msgNumber      & floatingVal.ToString("N"))
        Console.WriteLine(msgPercent     & floatingVal.ToString("P"))
        Console.WriteLine()
        
        ' Display the same values using a CultureInfo object. The CultureInfo class 
        ' implements IFormatProvider.
        Console.WriteLine(msg2)
        
        ' Display the culture used to format the values. 
        ' Create a European culture and change its currency symbol to "euro" because 
        ' this particular code example uses a thread current UI culture that cannot 
        ' display the euro symbol (€).
        ci = New CultureInfo("de-DE")
        ci.NumberFormat.CurrencySymbol = "euro"
        Console.WriteLine("{0,-26}{1}", msgCulture, ci.DisplayName)
        
        ' Display the integral and floating-point values.
        Console.WriteLine("{0,-26}{1}", msgIntegralVal, integralVal)
        Console.WriteLine("{0,-26}{1}", msgFloatingVal, floatingVal)
        Console.WriteLine()
        
        ' Use the format specifiers that are only for integral types.
        Console.WriteLine("Format specifiers only for integral types:")
        Console.WriteLine(msgDecimal     & integralVal.ToString("D", ci))
        Console.WriteLine(msgHexadecimal & integralVal.ToString("X", ci))
        Console.WriteLine()
        
        ' Use the format specifier that is only for the Single and Double 
        ' floating-point types.
        Console.WriteLine("Format specifier only for the Single and Double types:")
        Console.WriteLine(msgRoundTrip   & floatingVal.ToString("R", ci))
        Console.WriteLine()
        
        ' Use the format specifiers that are for integral or floating-point types.
        Console.WriteLine("Format specifiers for integral or floating-point types:")
        Console.WriteLine(msgCurrency    & floatingVal.ToString("C", ci))
        Console.WriteLine(msgScientific  & floatingVal.ToString("E", ci))
        Console.WriteLine(msgFixedPoint  & floatingVal.ToString("F", ci))
        Console.WriteLine(msgGeneral     & floatingVal.ToString("G", ci))
        Console.WriteLine(msgNumber      & floatingVal.ToString("N", ci))
        Console.WriteLine(msgPercent     & floatingVal.ToString("P", ci))
        Console.WriteLine()
    End Sub 'Main
End Class 'Sample
'
'This code example produces the following results:
'
'Standard Numeric Format Specifiers:
'
'Use ToString(String) and the current thread culture.
'
'Culture:                  English (United States)
'Integral value:           -12345
'Floating-point value:     -1234.567
'
'Format specifiers only for integral types:
'(D) Decimal:. . . . . . . -12345
'(X) Hexadecimal:. . . . . FFFFCFC7
'
'Format specifier only for the Single and Double types:
'(R) Round-trip: . . . . . -1234.567
'
'Format specifiers for integral or floating-point types:
'(C) Currency: . . . . . . ($1,234.57)
'(E) Scientific: . . . . . -1.234567E+003
'(F) Fixed point:. . . . . -1234.57
'(G) General (default):. . -1234.567
'(N) Number: . . . . . . . -1,234.57
'(P) Percent:. . . . . . . -123,456.70 %
'
'Use ToString(String, IFormatProvider) and a specified culture.
'
'Culture:                  German (Germany)
'Integral value:           -12345
'Floating-point value:     -1234.567
'
'Format specifiers only for integral types:
'(D) Decimal:. . . . . . . -12345
'(X) Hexadecimal:. . . . . FFFFCFC7
'
'Format specifier only for the Single and Double types:
'(R) Round-trip: . . . . . -1234,567
'
'Format specifiers for integral or floating-point types:
'(C) Currency: . . . . . . -1.234,57 euro
'(E) Scientific: . . . . . -1,234567E+003
'(F) Fixed point:. . . . . -1234,57
'(G) General (default):. . -1234,567
'(N) Number: . . . . . . . -1.234,57
'(P) Percent:. . . . . . . -123.456,70%
'

// This code example demonstrates the ToString(String) and 
// ToString(String, IFormatProvider) methods for integral and
// floating-point numbers, in conjunction with the standard 
// numeric format specifiers.
// This code example uses the System.Int32 integral type and 
// the System.Double floating-point type, but would yield 
// similar results for any of the numeric types. The integral 
// numeric types are System.Byte, SByte, Int16, Int32, Int64, 
// UInt16, UInt32, and UInt64. The floating-point numeric types 
// are Decimal, Single, and Double.

using System;
using System.Globalization;
using System.Threading;

class Sample 
{
    public static void Main() 
    {
// Format a negative integer or floating-point number in various ways.
    int    integralVal = -12345;
    double floatingVal = -1234.567d;

    string msgCurrency =    "(C) Currency: . . . . . . ";
    string msgDecimal  =    "(D) Decimal:. . . . . . . ";
    string msgScientific =  "(E) Scientific: . . . . . ";
    string msgFixedPoint =  "(F) Fixed point:. . . . . ";
    string msgGeneral =     "(G) General (default):. . ";
    string msgNumber =      "(N) Number: . . . . . . . ";
    string msgPercent =     "(P) Percent:. . . . . . . ";
    string msgRoundTrip =   "(R) Round-trip: . . . . . ";
    string msgHexadecimal = "(X) Hexadecimal:. . . . . ";

    string msg1 = "Use ToString(String) and the current thread culture.\n";
    string msg2 = "Use ToString(String, IFormatProvider) and a specified culture.\n";
    string msgCulture     = "Culture:";
    string msgIntegralVal = "Integral value:";
    string msgFloatingVal = "Floating-point value:";

    CultureInfo ci;
//
    Console.Clear();
    Console.WriteLine("Standard Numeric Format Specifiers:\n");
// Display the values.
    Console.WriteLine(msg1);

// Display the thread current culture, which is used to format the values.
    ci = Thread.CurrentThread.CurrentCulture;
    Console.WriteLine("{0,-26}{1}", msgCulture, ci.DisplayName);

// Display the integral and floating-point values.
    Console.WriteLine("{0,-26}{1}", msgIntegralVal, integralVal);
    Console.WriteLine("{0,-26}{1}", msgFloatingVal, floatingVal);
    Console.WriteLine();

// Use the format specifiers that are only for integral types.
    Console.WriteLine("Format specifiers only for integral types:");
    Console.WriteLine(msgDecimal     + integralVal.ToString("D"));
    Console.WriteLine(msgHexadecimal + integralVal.ToString("X"));
    Console.WriteLine();

// Use the format specifier that is only for the Single and Double 
// floating-point types.
    Console.WriteLine("Format specifier only for the Single and Double types:");
    Console.WriteLine(msgRoundTrip   + floatingVal.ToString("R"));
    Console.WriteLine();

// Use the format specifiers that are for integral or floating-point types.
    Console.WriteLine("Format specifiers for integral or floating-point types:");
    Console.WriteLine(msgCurrency    + floatingVal.ToString("C"));
    Console.WriteLine(msgScientific  + floatingVal.ToString("E"));
    Console.WriteLine(msgFixedPoint  + floatingVal.ToString("F"));
    Console.WriteLine(msgGeneral     + floatingVal.ToString("G"));
    Console.WriteLine(msgNumber      + floatingVal.ToString("N"));
    Console.WriteLine(msgPercent     + floatingVal.ToString("P"));
    Console.WriteLine();

// Display the same values using a CultureInfo object. The CultureInfo class 
// implements IFormatProvider.
    Console.WriteLine(msg2);

// Display the culture used to format the values. 
// Create a European culture and change its currency symbol to "euro" because 
// this particular code example uses a thread current UI culture that cannot 
// display the euro symbol (€).
    ci = new CultureInfo("de-DE");
    ci.NumberFormat.CurrencySymbol = "euro";
    Console.WriteLine("{0,-26}{1}", msgCulture, ci.DisplayName);

// Display the integral and floating-point values.
    Console.WriteLine("{0,-26}{1}", msgIntegralVal, integralVal);
    Console.WriteLine("{0,-26}{1}", msgFloatingVal, floatingVal);
    Console.WriteLine();

// Use the format specifiers that are only for integral types.
    Console.WriteLine("Format specifiers only for integral types:");
    Console.WriteLine(msgDecimal     + integralVal.ToString("D", ci));
    Console.WriteLine(msgHexadecimal + integralVal.ToString("X", ci));
    Console.WriteLine();

// Use the format specifier that is only for the Single and Double 
// floating-point types.
    Console.WriteLine("Format specifier only for the Single and Double types:");
    Console.WriteLine(msgRoundTrip   + floatingVal.ToString("R", ci));
    Console.WriteLine();

// Use the format specifiers that are for integral or floating-point types.
    Console.WriteLine("Format specifiers for integral or floating-point types:");
    Console.WriteLine(msgCurrency    + floatingVal.ToString("C", ci));
    Console.WriteLine(msgScientific  + floatingVal.ToString("E", ci));
    Console.WriteLine(msgFixedPoint  + floatingVal.ToString("F", ci));
    Console.WriteLine(msgGeneral     + floatingVal.ToString("G", ci));
    Console.WriteLine(msgNumber      + floatingVal.ToString("N", ci));
    Console.WriteLine(msgPercent     + floatingVal.ToString("P", ci));
    Console.WriteLine();
    }
}
/*
This code example produces the following results:

Standard Numeric Format Specifiers:

Use ToString(String) and the current thread culture.

Culture:                  English (United States)
Integral value:           -12345
Floating-point value:     -1234.567

Format specifiers only for integral types:
(D) Decimal:. . . . . . . -12345
(X) Hexadecimal:. . . . . FFFFCFC7

Format specifier only for the Single and Double types:
(R) Round-trip: . . . . . -1234.567

Format specifiers for integral or floating-point types:
(C) Currency: . . . . . . ($1,234.57)
(E) Scientific: . . . . . -1.234567E+003
(F) Fixed point:. . . . . -1234.57
(G) General (default):. . -1234.567
(N) Number: . . . . . . . -1,234.57
(P) Percent:. . . . . . . -123,456.70 %

Use ToString(String, IFormatProvider) and a specified culture.

Culture:                  German (Germany)
Integral value:           -12345
Floating-point value:     -1234.567

Format specifiers only for integral types:
(D) Decimal:. . . . . . . -12345
(X) Hexadecimal:. . . . . FFFFCFC7

Format specifier only for the Single and Double types:
(R) Round-trip: . . . . . -1234,567

Format specifiers for integral or floating-point types:
(C) Currency: . . . . . . -1.234,57 euro
(E) Scientific: . . . . . -1,234567E+003
(F) Fixed point:. . . . . -1234,57
(G) General (default):. . -1234,567
(N) Number: . . . . . . . -1.234,57
(P) Percent:. . . . . . . -123.456,70%

*/

Vedere anche

Riferimenti

NumberFormatInfo

Concetti

Stringhe di formato numerico
Esempi di output di stringhe di formato numerico standard
Stringhe di formato numerico personalizzato

Altre risorse

Formattazione dei tipi di dati