EncoderReplacementFallback Class
Provides a failure handling mechanism, called a fallback, for an input character that cannot be converted to an output byte sequence. The fallback uses a user-specified replacement string instead of the original input character. This class cannot be inherited.
Assembly: mscorlib (in mscorlib.dll)
The EncoderReplacementFallback type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | EncoderReplacementFallback() | Initializes a new instance of the EncoderReplacementFallback class. |
![]() | EncoderReplacementFallback(String) | Initializes a new instance of the EncoderReplacementFallback class using a specified replacement string. |
| Name | Description | |
|---|---|---|
![]() | DefaultString | Gets the replacement string that is the value of the EncoderReplacementFallback object. |
![]() | MaxCharCount | Gets the number of characters in the replacement string for the EncoderReplacementFallback object. (Overrides EncoderFallback::MaxCharCount.) |
| Name | Description | |
|---|---|---|
![]() | CreateFallbackBuffer | Creates a EncoderFallbackBuffer object that is initialized with the replacement string of this EncoderReplacementFallback object. (Overrides EncoderFallback::CreateFallbackBuffer().) |
![]() | Equals | Indicates whether the value of a specified object is equal to the EncoderReplacementFallback object. (Overrides Object::Equals(Object).) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.) |
![]() | GetHashCode | Retrieves the hash code for the value of the EncoderReplacementFallback object. (Overrides Object::GetHashCode().) |
![]() | GetType | Gets the Type of the current instance. (Inherited from Object.) |
![]() | MemberwiseClone | Creates a shallow copy of the current Object. (Inherited from Object.) |
![]() | ToString | Returns a string that represents the current object. (Inherited from Object.) |
A common reason for an encoding or decoding operation to fail is if the underlying encoding class does not provide a mapping between a character and an equivalent byte sequence. For example, an ASCIIEncoding object cannot encode a character having a Unicode code point value that is outside the range U+0000 to U+007F. If the input character cannot be converted to an output byte sequence, a EncoderReplacementFallback object substitutes a specified replacement string for the original input character. The conversion process encodes the replacement string and then continues to process the remainder of the original input.
The value of a EncoderReplacementFallback object is the replacement string used to initialize that object.
This class is one of two .NET Framework classes that implement different fallback strategies for handling encoding conversion failures. The other class is the EncoderExceptionFallback class, which throws an EncoderFallbackException when an invalid character is encountered.
When you choose a fallback string to use with this class, make sure that the string is composed entirely of characters that can be encoded in the target encoding. Otherwise, a recursive fallback results, causing an ArgumentException.
The following code example demonstrates the EncoderReplacementFallback class.
// This example demonstrates the EncoderReplacementFallback class. using namespace System; using namespace System::Text; int main() { // Create an encoding, which is equivalent to calling the // ASCIIEncoding class constructor. // The EncoderReplacementFallback parameter specifies that the // string, "(unknown)", replace characters that cannot be encoded. // A decoder replacement fallback is also specified, but in this // code example the decoding operation cannot fail. Encoding^ ascii = Encoding::GetEncoding("us-ascii", gcnew EncoderReplacementFallback("(unknown)"), gcnew DecoderReplacementFallback("(error)")); // 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 are replaced with the fallback replacement string, // "(unknown)". String^ inputString = "\u00abX\u00bb"; String^ decodedString; String^ twoNewLines = Environment::NewLine + Environment::NewLine; array <Byte>^ encodedBytes = gcnew array<Byte>(ascii->GetByteCount(inputString)); int numberOfEncodedBytes = 0; // --------------------------------------------------------------------- Console::Clear(); // Display the name of the encoding. Console::WriteLine("The name of the encoding is \"{0}\".{1}", ascii->WebName, Environment::NewLine); // Display the input string in text. Console::WriteLine("Input string ({0} characters): \"{1}\"", inputString->Length, inputString); // Display the input string in hexadecimal. Console::Write("Input string in hexadecimal: "); for each (char c in inputString) { Console::Write("0x{0:X2} ", c); } Console::Write(twoNewLines); // --------------------------------------------------------------------- // Encode the input string. Console::WriteLine("Encode the input string..."); numberOfEncodedBytes = ascii->GetBytes(inputString, 0, inputString->Length, encodedBytes, 0); // Display the encoded bytes. Console::WriteLine("Encoded bytes in hexadecimal ({0} bytes):{1}", numberOfEncodedBytes, Environment::NewLine); for(int i = 0; i < encodedBytes->Length; i++) { Console::Write("0x{0:X2} ", encodedBytes[i]); if(((i + 1) % 6) == 0) { Console::WriteLine(); } } Console::Write(twoNewLines); // --------------------------------------------------------------------- // Decode the encoded bytes, yielding a reconstituted string. Console::WriteLine("Decode the encoded bytes..."); decodedString = ascii->GetString(encodedBytes); // Display the input string and the decoded string for comparison. Console::WriteLine("Input string: \"{0}\"", inputString); Console::WriteLine("Decoded string:\"{0}\"", decodedString); } /* 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... Encoded bytes in hexadecimal (19 bytes): 0x28 0x75 0x6E 0x6B 0x6E 0x6F 0x77 0x6E 0x29 0x58 0x28 0x75 0x6E 0x6B 0x6E 0x6F 0x77 0x6E 0x29 Decode the encoded bytes... Input string: "X" Decoded string:"(unknown)X(unknown)" */
Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2
The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.
