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DecoderFallbackException Class

The exception that is thrown when a decoder fallback operation fails. This class cannot be inherited.

System.Object
  System.Exception
    System.SystemException
      System.ArgumentException
        System.Text.DecoderFallbackException

Namespace:  System.Text
Assemblies:   System.Text.Encoding (in System.Text.Encoding.dll)
  mscorlib (in mscorlib.dll)

'Declaration
Public NotInheritable Class DecoderFallbackException _
	Inherits ArgumentException

The DecoderFallbackException type exposes the following members.

  NameDescription
Public methodSupported by Portable Class LibraryDecoderFallbackExceptionInitializes a new instance of the DecoderFallbackException class.
Public methodSupported by Portable Class LibraryDecoderFallbackException(String)Initializes a new instance of the DecoderFallbackException class. A parameter specifies the error message.
Public methodSupported by Portable Class LibraryDecoderFallbackException(String, Exception)Initializes a new instance of the DecoderFallbackException class. Parameters specify the error message and the inner exception that is the cause of this exception.
Public methodSupported by Portable Class LibraryDecoderFallbackException(String, Byte(), Int32)Initializes a new instance of the DecoderFallbackException class. Parameters specify the error message, the array of bytes being decoded, and the index of the byte that cannot be decoded.
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  NameDescription
Public propertySupported by Portable Class LibraryBytesUnknownGets the input byte sequence that caused the exception.
Public propertySupported by Portable Class LibraryDataGets a collection of key/value pairs that provide additional user-defined information about the exception. (Inherited from Exception.)
Public propertySupported by Portable Class LibraryHelpLinkGets or sets a link to the help file associated with this exception. (Inherited from Exception.)
Public propertyHResultGets or sets HRESULT, a coded numerical value that is assigned to a specific exception. (Inherited from Exception.)
Public propertySupported by Portable Class LibraryIndexGets the index position in the input byte sequence of the byte that caused the exception.
Public propertySupported by Portable Class LibraryInnerExceptionGets the Exception instance that caused the current exception. (Inherited from Exception.)
Public propertySupported by Portable Class LibraryMessageGets the error message and the parameter name, or only the error message if no parameter name is set. (Inherited from ArgumentException.)
Public propertySupported by Portable Class LibraryParamNameGets the name of the parameter that causes this exception. (Inherited from ArgumentException.)
Public propertySupported by Portable Class LibrarySourceGets or sets the name of the application or the object that causes the error. (Inherited from Exception.)
Public propertySupported by Portable Class LibraryStackTraceGets a string representation of the immediate frames on the call stack. (Inherited from Exception.)
Public propertyTargetSiteGets the method that throws the current exception. (Inherited from Exception.)
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  NameDescription
Public methodSupported by Portable Class LibraryEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodSupported by Portable Class LibraryGetBaseExceptionWhen overridden in a derived class, returns the Exception that is the root cause of one or more subsequent exceptions. (Inherited from Exception.)
Public methodSupported by Portable Class LibraryGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetObjectDataSets the SerializationInfo object with the parameter name and additional exception information. (Inherited from ArgumentException.)
Public methodGetTypeGets the runtime type of the current instance. (Inherited from Exception.)
Public methodSupported by Portable Class LibraryToStringCreates and returns a string representation of the current exception. (Inherited from Exception.)
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The following code example demonstrates the DecoderExceptionFallback and DecoderFallbackException classes.

' This example demonstrates the DecoderExceptionFallback 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 DecoderExceptionFallback parameter specifies that an exception 
        ' is thrown if a character cannot be encoded.  
        ' An encoder exception fallback is also specified, but in this code 
        ' example the encoding operation cannot fail.   


        Dim eef As New EncoderExceptionFallback()
        Dim def As New DecoderExceptionFallback()
        Dim ae As Encoding = Encoding.GetEncoding("us-ascii", eef, def)
        Dim inputString As String = "XYZ" 
        Dim decodedString As String 
        Dim twoNewLines As String = vbCrLf & vbCrLf
        Dim numberOfEncodedBytes As Integer = ae.GetByteCount(inputString)
        ' 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)

        ' -------------------------------------------------------------------------- 
        ' Encode the input string. 
        Console.WriteLine("Encode the input string...")
        numberOfEncodedBytes = ae.GetBytes(inputString, 0, inputString.Length, _
                                           encodedBytes, 0)
        ' Display the encoded bytes. 
        ' Each element is converted to an integer with Convert.ToInt32.
        Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):" & vbCrLf, _
                           numberOfEncodedBytes)
        Dim b As Byte 
        For Each b In  encodedBytes
            Console.Write("0x{0:X2} ", Convert.ToInt32(b))
        Next b
        Console.Write(twoNewLines)

        ' -------------------------------------------------------------------------- 
        ' Replace the encoded byte sequences for the characters 'X' and 'Z' with the  
        ' value 0xFF, which is outside the valid range of 0x00 to 0x7F for  
        ' ASCIIEncoding. The resulting byte sequence is actually the beginning of  
        ' this code example because it is the input to the decoder operation, and  
        ' is equivalent to a corrupted or improperly encoded byte sequence. 

        encodedBytes(0) = &HFF
        encodedBytes(2) = &HFF

        Console.WriteLine("Display the corrupted byte sequence...")
        ' Each element is converted to an integer with Convert.ToInt32.
        Console.WriteLine("Encoded bytes in hexadecimal ({0} bytes):" & vbCrLf, _
                           numberOfEncodedBytes)
        For Each b In  encodedBytes
            Console.Write("0x{0:X2} ", Convert.ToInt32(b))
        Next b
        Console.Write(twoNewLines)

        ' -------------------------------------------------------------------------- 
        ' Attempt to decode the encoded bytes. However, an exception is thrown  
        ' before the byte sequence can be decoded.
        Console.WriteLine("Compare the decoded bytes to the input string...")

        Try
            decodedString = ae.GetString(encodedBytes)
        Catch dfe As DecoderFallbackException
            Console.WriteLine(dfe)
            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): "XYZ" 
'Input string in hexadecimal: 0x58 0x59 0x5A 

'Encode the input string... 
'Encoded bytes in hexadecimal (3 bytes): 

'0x58 0x59 0x5A 

'Display the corrupted byte sequence... 
'Encoded bytes in hexadecimal (3 bytes): 

'0xFF 0x59 0xFF 

'Compare the decoded bytes to the input string... 
'System.Text.DecoderFallbackException: Unable to translate bytes [FF] at index 0 from speci 
'fied code page to Unicode. 
'   at System.Text.DecoderExceptionFallbackBuffer.Throw(Byte[] bytesUnknown, Int32 index) 
'   at System.Text.DecoderExceptionFallbackBuffer.Fallback(Byte[] bytesUnknown, Int32 index 
') 
'   at System.Text.DecoderFallbackBuffer.InternalFallback(Byte[] bytes, Byte* pBytes) 
'   at System.Text.ASCIIEncoding.GetCharCount(Byte* bytes, Int32 count, DecoderNLS decoder) 

'   at System.String.CreateStringFromEncoding(Byte* bytes, Int32 byteLength, Encoding encod 
'ing) 
'   at System.Text.ASCIIEncoding.GetString(Byte[] bytes, Int32 byteIndex, Int32 byteCount) 
'   at System.Text.Encoding.GetString(Byte[] bytes) 
'   at Sample.Main() 

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

'

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Portable Class Library

Supported in: Portable Class Library

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