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EncoderFallbackException Class

The exception that is thrown when an encoder fallback operation fails. This class cannot be inherited.

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

'Declaration
<SerializableAttribute> _
Public NotInheritable Class EncoderFallbackException _
	Inherits ArgumentException
'Usage
Dim instance As EncoderFallbackException

The following code example demonstrates the EncoderExceptionFallback and EncoderFallbackException classes.

' This example demonstrates the EncoderExceptionFallback class. 
Imports System
Imports System.Text

Class Sample
    Public Shared Sub Main() 

        ' Create an encoding, which is equivalent to calling the  
        ' ASCIIEncoding class constructor.  
        ' The EncoderExceptionFallback parameter causes an exception to 
        ' be thrown when a character cannot be encoded.  
        ' A decoder exception fallback is also specified, but it is not  
        ' used because this example terminates during the encoding operation.   


        Dim eef As New EncoderExceptionFallback()
        Dim def As New DecoderExceptionFallback()
        Dim ae As Encoding = Encoding.GetEncoding("us-ascii", eef, def)

        ' The input string consists of the Unicode characters LEFT POINTING  
        ' DOUBLE ANGLE QUOTATION MARK (U+00AB), 'X' (U+0058), and RIGHT POINTING  
        ' DOUBLE ANGLE QUOTATION MARK (U+00BB).  
        ' The encoding can only encode characters in the US-ASCII range of U+0000  
        ' through U+007F. Consequently, the characters bracketing the 'X' character 
        ' cause an exception. 

        Dim inputString As String = "«X»" 

        Dim twoNewLines As String = vbCrLf & vbCrLf
        Dim numberOfEncodedBytes As Integer = ae.GetMaxByteCount(inputString.Length)
        ' Counteract the compiler adding an extra element. 
        Dim encodedBytes(numberOfEncodedBytes - 1) As Byte

        ' --------------------------------------------------------------------------
        Console.Clear()

        ' Display the name of the encoding.
        Console.WriteLine("The name of the encoding is ""{0}""." & vbCrLf, ae.WebName)

        ' Display the input string in text.
        Console.WriteLine("Input string ({0} characters): ""{1}""", _
                           inputString.Length, inputString)

        ' Display the input string in hexadecimal.  
        ' Each element is converted to an integer with Convert.ToInt32.
        Console.Write("Input string in hexadecimal: ")
        Dim c As Char 
        For Each c In  inputString.ToCharArray()
            Console.Write("0x{0:X2} ", Convert.ToInt32(c))
        Next c
        Console.Write(twoNewLines)

        ' -------------------------------------------------------------------------- 
        ' Attempt to encode the input string. However, an exception is thrown before 
        ' the input string can be encoded.
        Console.WriteLine("Encode the input string...")

        ' The code example terminates during the call to the GetBytes() method. 
        Try
            numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length, _
                                               encodedBytes, 0)
        Catch e As EncoderFallbackException
            Console.WriteLine(e)
            Console.WriteLine(vbCrLf & _
                              "*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED. ***")
            Return 
        End Try 

        ' This statement is never executed.
        Console.WriteLine("This statement is never executed.")

    End Sub 'Main
End Class 'Sample

'This code example produces the following results: 

'The name of the encoding is "us-ascii". 

'Input string (3 characters): "X" 
'Input string in hexadecimal: 0xAB 0x58 0xBB 

'Encode the input string... 
'System.Text.EncoderFallbackException: Unable to translate Unicode character \u00AB at inde 
'x 0 to specified code page. 
'   at System.Text.EncoderExceptionFallbackBuffer.Fallback(Char charUnknown, Int32 index) 
'   at System.Text.EncoderFallbackBuffer.InternalFallback(Char ch, Char*& chars) 
'   at System.Text.ASCIIEncoding.GetBytes(Char* chars, Int32 charCount, Byte* bytes, Int32 
'byteCount, EncoderNLS encoder) 
'   at System.Text.ASCIIEncoding.GetBytes(String chars, Int32 charIndex, Int32 charCount, B 
'yte[] bytes, Int32 byteIndex) 
'   at Sample.Main() 

'*** THE CODE EXAMPLE TERMINATES HERE AS INTENDED. *** 
'

System.Object
  System.Exception
    System.SystemException
      System.ArgumentException
        System.Text.EncoderFallbackException

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

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

.NET Framework

Supported in: 3.5, 3.0, 2.0
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