It might not be possible to convert an encoded byte sequence to an equivalent character if no suitable decoding exists. A common reason for a decoding to fail is that the conversion operation uses a code page that cannot represent the character to decode.

If the input byte sequence cannot be converted to an output character, a System.Text.DecoderReplacementFallback object provides a replacement string that is substituted for the output character. The replacement string initializes the value of the System.Text.DecoderReplacementFallback object, and the value of the System.Text.DecoderReplacementFallback object initializes the value of a System.Text.DecoderReplacementFallbackBuffer object. The value of a System.Text.DecoderReplacementFallbackBuffer object is called the replacement fallback buffer. The conversion operation uses the replacement fallback buffer to emit a replacement string instead of a decoded character, then continues to process the remainder of the input.

Namespace: System.Text
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 2.0.0.0, 4.0.0.0
Since: .NET 2.0