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IFormatProvider.GetFormat Method

Gets an object that provides formatting services for the specified type.

Namespace: System
Assembly: mscorlib (in mscorlib.dll)

'Declaration
Function GetFormat ( _
	formatType As Type _
) As Object
'Usage
Dim instance As IFormatProvider
Dim formatType As Type
Dim returnValue As Object

returnValue = instance.GetFormat(formatType)
Object GetFormat (
	Type formatType
)
function GetFormat (
	formatType : Type
) : Object

Parameters

formatType

An object that specifies the type of format object to get.

Return Value

The current instance, if formatType is the same type as the current instance; otherwise, a null reference (Nothing in Visual Basic).

Implement this method in classes that use format objects in methods that either generate or parse string representations of objects. The ToString and Parse methods are examples of these types of methods.

For more information, see the CultureInfo.CurrentCulture topic.

The following code example illustrates the use of a class that implements the IFormatProvider interface and the GetFormat method. The AnyRadix class supports the "Ra" formatting code and converts an Int64 value to a string of any specified radix between 2 and 36. GetFormat returns a reference to itself if the Type parameter refers to a class that implements ICustomFormatter; otherwise, GetFormat returns a null reference (Nothing in Visual Basic).

' Sample for the IFormatProvider interface and
' the IFormatProvider.GetFormat( Type ) method.
Imports System
Imports Microsoft.VisualBasic

' This class implements the "Ra" formatting code. An instance of this 
' class should be passed to methods requiring an IFormatProvider.
Public Class AnyRadix
    Implements ICustomFormatter 
    Implements IFormatProvider

    ' The value to be formatted is returned as a signed string 
    ' of digits from the rDigits array. 
    Const radixCode As String = "Ra"
    Private Shared rDigits As Char( ) = { _
        "0"c, "1"c, "2"c, "3"c, "4"c, "5"c, "6"c, "7"c, "8"c, _
        "9"c, "A"c, "B"c, "C"c, "D"c, "E"c, "F"c, "G"c, "H"c, _
        "I"c, "J"c, "K"c, "L"c, "M"c, "N"c, "O"c, "P"c, "Q"c, _
        "R"c, "S"c, "T"c, "U"c, "V"c, "W"c, "X"c, "Y"c, "Z"c }
        
    ' This method returns an object that implements ICustomFormatter 
    ' to do the formatting. 
    Public Function GetFormat( argType As Type ) As Object _
        Implements IFormatProvider.GetFormat

        ' Here, the same object (Me) is returned, but it would be 
        ' possible to return an object of a different type.
        If argType Is GetType( ICustomFormatter ) Then
            Return Me
        Else
            Return Nothing
        End If
    End Function 
        
    ' This method does the formatting only if it recognizes the 
    ' format codes. 
    Public Function Format( formatString As String, _
        argToBeFormatted As Object, _
        provider As IFormatProvider ) As String _
        Implements ICustomFormatter.Format
            
        ' If no format string is provided or the format string cannot 
        ' be handled, use IFormattable or standard string processing.
        If formatString Is Nothing OrElse _
            Not formatString.Trim( ).StartsWith( radixCode ) Then

            If TypeOf argToBeFormatted Is IFormattable Then
                Return CType( argToBeFormatted, IFormattable ). _
                    ToString( formatString, provider )
            Else
                Return argToBeFormatted.ToString( )
            End If
        End If 

        ' The formatting is handled here.
        Dim digitIndex          As Integer = 0
        Dim radix               As Long 
        Dim longToBeFormatted   As Long 
        Dim longPositive        As Long
        Dim outDigits( 63 )     As Char
            
        ' Extract the radix from the format string.
        formatString = formatString.Replace( radixCode, "" )
        Try
            radix = Convert.ToInt64( formatString )
        Catch ex As Exception
            Throw New ArgumentException( String.Format( _
                "The radix ""{0}"" is invalid.", _
                formatString ), ex )
        End Try

        ' Verify that the radix is in the proper range.
        If radix < 2 OrElse radix > 36 Then
            Throw New ArgumentException( String.Format( _
                "The radix ""{0}"" is not in the range 2..36.", _
                formatString ) )
        End If
            
        ' Verify that the argument can be converted to a long integer.
        Try
            longToBeFormatted = CType( argToBeFormatted, Long )
        Catch ex As Exception
            Throw New ArgumentException( String.Format( _
                "The argument ""{0}"" cannot be " & _
                "converted to an integer value.", _
                argToBeFormatted ), ex )
        End Try
            
        ' Extract the magnitude for conversion.
        longPositive = Math.Abs( longToBeFormatted )

        ' Convert the magnitude to a digit string.
        For digitIndex = 0 To 64
            If longPositive = 0 Then Exit For

            outDigits( outDigits.Length - digitIndex - 1 ) = _
                rDigits( longPositive Mod radix )
            longPositive \= radix
        Next digitIndex
            
        ' Add a minus sign if the argument is negative.
        If longToBeFormatted < 0 Then
            outDigits( outDigits.Length - digitIndex - 1 ) = "-"c 
            digitIndex += 1
        End If 

        Return New String( outDigits, _
            outDigits.Length - digitIndex, digitIndex )
    End Function 
End Class

Module IFormatProviderDemo
    
    Sub ConvertToAnyRadix( argToConvert As Object, _
        formatStr As String )

        Dim provider As New AnyRadix( )
        Dim messageStr As String = _
            String.Format( "{{0:{0}}}", formatStr )

        ' Write the first part of the output line.
        Console.Write( "{0,18}  {1,-6}", _ 
            argToConvert, formatStr )

        ' Convert the specified argument using the specified format.
        Try
            Console.WriteLine( String.Format( _
                provider, messageStr, argToConvert ) )
        Catch ex As Exception
            Dim lineEnd As Integer = _
                ex.ToString( ).IndexOf( vbLf )
            Console.WriteLine( _
                ex.ToString( ).Substring( 0, lineEnd ) )
            Console.WriteLine( )
        End Try
    End Sub 
        
    Sub Main( )
        Dim TwoToThe32      As Long = 4294967296
        Dim fifteenNines    As Long = 999999999999999
            
        Console.WriteLine( _
            "This example of the IFormatProvider interface " & _
            vbCrLf & "and the IFormatProvider." & _
            "GetFormat( Type ) method " & vbCrLf & _
            "generates the following output." & vbCrLf )
        Console.WriteLine( "{0,18} Format Result", "Number" )
        Console.WriteLine( "{0,18} ------ ------", "------" )
            
        ' These are valid conversions.
        ConvertToAnyRadix( TwoToThe32, "Ra2" )
        ConvertToAnyRadix( TwoToThe32, "Ra5" )
        ConvertToAnyRadix( TwoToThe32, "Ra16" )
        ConvertToAnyRadix( TwoToThe32, "Ra23" )
        ConvertToAnyRadix( TwoToThe32, "Ra36" )
        ConvertToAnyRadix( fifteenNines, "Ra2" )
        ConvertToAnyRadix( fifteenNines, "Ra3" )
        ConvertToAnyRadix( fifteenNines, "Ra8" )
        ConvertToAnyRadix( fifteenNines, "Ra11" )
        ConvertToAnyRadix( fifteenNines, "Ra16" )
        ConvertToAnyRadix( fifteenNines, "Ra23" )
        ConvertToAnyRadix( fifteenNines, "Ra36" )
        ConvertToAnyRadix( fifteenNines, "E16" )
        ConvertToAnyRadix( fifteenNines, "" )
            
        ' These are error conditions.
        ConvertToAnyRadix( fifteenNines, "Ra37" )
        ConvertToAnyRadix( "ABCDEFGHIJKLM", "Ra16" )
    End Sub 
End Module 

' This example of the IFormatProvider interface
' and the IFormatProvider.GetFormat( Type ) method
' generates the following output.
' 
'             Number Format Result
'             ------ ------ ------
'         4294967296  Ra2   100000000000000000000000000000000
'         4294967296  Ra5   32244002423141
'         4294967296  Ra16  100000000
'         4294967296  Ra23  1606K7IC
'         4294967296  Ra36  1Z141Z4
'    999999999999999  Ra2   11100011010111111010100100110001100111111111111111
'    999999999999999  Ra3   11212010201001210101011021212000
'    999999999999999  Ra8   34327724461477777
'    999999999999999  Ra11  26A6A3689065639
'    999999999999999  Ra16  38D7EA4C67FFF
'    999999999999999  Ra23  1134DIFHLMM4
'    999999999999999  Ra36  9UGXNORJLR
'    999999999999999  E16   9.9999999999999900E+014
'    999999999999999        999999999999999
'    999999999999999  Ra37  System.ArgumentException: The radix "37" is not in
' the range 2..36.
' 
'      ABCDEFGHIJKLM  Ra16  System.ArgumentException: The argument "ABCDEFGHIJK
' LM" cannot be converted to an integer value. ---> System.InvalidCastException
' : Cast from string "ABCDEFGHIJKLM" to type 'Long' is not valid. ---> System.F
' ormatException: Input string was not in a correct format.

// Sample for the IFormatProvider interface and
// the IFormatProvider.GetFormat( Type ) method.
import System.*;

// This class implements the "Ra" formatting code. An instance of this
// class should be passed to methods requiring an IFormatProvider.
public class AnyRadix implements ICustomFormatter,IFormatProvider
{
    // The value to be formatted is returned as a signed string 
    // of digits from the rDigits array. 
    private String radixCode = "Ra";
    private static char rDigits[] = {
        '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 
        'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 
        'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 
        'U', 'V', 'W', 'X', 'Y', 'Z' };
   
    // This method returns an object that implements ICustomFormatter 
    // to do the formatting. 
    public Object GetFormat(Type argType)
    {
        // Here, the same object (this) is returned, but it would 
        // be possible to return an object of a different type.
        if ( argType.Equals(ICustomFormatter.class.ToType()) ) {
            return this ;
        }
        else {
            return null ;
        }
    } //GetFormat
    
    // This method does the formatting only if it recognizes the 
    // format codes. 
    public String Format(String formatString, Object argToBeFormatted,
                        IFormatProvider provider) 
    {
        // If no format string is provided or the format string cannot 
        // be handled, use IFormattable or standard string processing.
        if(formatString == null||!(formatString.Trim().StartsWith(radixCode))) {
            if ( argToBeFormatted instanceof IFormattable  ) {
                return((IFormattable)(argToBeFormatted)).
                    ToString(formatString,provider);
            }
            else {
                return argToBeFormatted.ToString();
            }
        }

        // The formatting is handled here.
        int digitIndex = 0;
        long radix;
        long longToBeFormatted;
        long longPositive;
        char outDigits[] = new char[63];
      
        // Extract the radix from the format string.
        formatString = formatString.Replace(radixCode, "");
        try {
            radix = Convert.ToInt64(formatString);
        }
        catch(System.Exception  ex) {
            throw new ArgumentException(String.Format(
                "The radix \"{0}\" is invalid.", formatString), ex);
        }
      
        // Verify that the radix is in the proper range.
        if ( radix < 2 || radix > 36  ) {
            throw new ArgumentException(String.Format(
                "The radix \"{0}\" is not in the range 2..36.", formatString));
        }
      
        // Verify that the argument can be converted to a long integer.
        try {
            longToBeFormatted =(long)System.Convert.ToUInt64(argToBeFormatted);
        }
        catch(System.Exception  ex) {
            throw new ArgumentException(String.Format(
                "The argument \"{0}\" cannot be "
                + "converted to an integer value.", argToBeFormatted), ex);
        }
      
        // Extract the magnitude for conversion.
        longPositive = System.Math.Abs(longToBeFormatted);

        // Convert the magnitude to a digit string.
        for(digitIndex = 0;digitIndex <= 64;digitIndex++) {
            if ( longPositive == 0  ) {
                break ;
            }        
            outDigits[outDigits.length - digitIndex - 1] = 
                rDigits[(int)(longPositive % radix)];
            longPositive /= radix;
        }      
        // Add a minus sign if the argument is negative.
        if ( longToBeFormatted < 0  ) {
            outDigits [outDigits.length - digitIndex ++ - 1] = '-';
        }      
        return new String(outDigits, outDigits.length - digitIndex, digitIndex);
    } //Format
} //AnyRadix

class IFormatProviderDemo
{   
    static void ConvertToAnyRadix(Object argToConvert, String formatStr) 
    {
        AnyRadix provider = new AnyRadix();        
        String messageStr = String.Format("{{0:{0}}}", formatStr);
        
        // Write the first part of the output line.
        Console.Write("{0,18}  {1,-6}", argToConvert, formatStr);
        
        // Convert the specified argument using the specified format.
        try {
            Console.WriteLine(String.Format((IFormatProvider)provider,
                messageStr,new Object[]{ argToConvert}));
        }
        catch(System.Exception ex) {
            // Display the exception without the stack trace.
            int lineEnd = ex.ToString().IndexOf('\n');            
            Console.WriteLine("{0}\n", ex.ToString().Substring(0, lineEnd));
        }
    } //ConvertToAnyRadix  
   
    public static void main(String[] args)
    {
        long twoToThe32 = 4294967296L;
        long fifteenNines = 999999999999999L;

        Console.WriteLine(("This example of the IFormatProvider interface \n"
            + "and the IFormatProvider.GetFormat( Type ) method "
            + "\ngenerates the following output.\n"));
        Console.WriteLine("{0,18} Format Result", "Number");
        Console.WriteLine("{0,18} ------ ------", "------");

        // These are valid conversions.
        ConvertToAnyRadix(((System.UInt64 )(twoToThe32)), "Ra2");
        ConvertToAnyRadix(((System.UInt64)(twoToThe32)), "Ra5");
        ConvertToAnyRadix(((System.UInt64)(twoToThe32)), "Ra16");
        ConvertToAnyRadix(((System.UInt64)(twoToThe32)), "Ra23");
        ConvertToAnyRadix(((System.UInt64)(twoToThe32)), "Ra36");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra2");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra3");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra8");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra11");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra16");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra23");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra36");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "E16");
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "");

        // These are error conditions.
        ConvertToAnyRadix(((System.UInt64)(fifteenNines)), "Ra37");
        ConvertToAnyRadix("ABCDEFGHIJKLM", "Ra16");
    } //main
} //IFormatProviderDemo

/*
This example of the IFormatProvider interface
and the IFormatProvider.GetFormat( Type ) method
generates the following output.

            Number Format Result
            ------ ------ ------
        4294967296  Ra2   100000000000000000000000000000000
        4294967296  Ra5   32244002423141
        4294967296  Ra16  100000000
        4294967296  Ra23  1606K7IC
        4294967296  Ra36  1Z141Z4
   999999999999999  Ra2   11100011010111111010100100110001100111111111111111
   999999999999999  Ra3   11212010201001210101011021212000
   999999999999999  Ra8   34327724461477777
   999999999999999  Ra11  26A6A3689065639
   999999999999999  Ra16  38D7EA4C67FFF
   999999999999999  Ra23  1134DIFHLMM4
   999999999999999  Ra36  9UGXNORJLR
   999999999999999  E16   9.9999999999999900E+014
   999999999999999        999999999999999
   999999999999999  Ra37  System.ArgumentException: The radix "37" is not in th
e range 2..36.

     ABCDEFGHIJKLM  Ra16  System.ArgumentException: The argument "ABCDEFGHIJKLM"
 cannot be converted to an integer value. ---> System.FormatException: Input str
ing was not in a correct format.
*/

Windows 98, Windows 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

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