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

If the input character cannot be converted to an output byte sequence, a System.Text.EncoderReplacementFallback object provides a replacement string that is substituted for the original input character. The replacement string initializes the value of the System.Text.EncoderReplacementFallback object, and the value of the System.Text.EncoderReplacementFallback object initializes the value of an System.Text.EncoderReplacementFallbackBuffer object. The value of an System.Text.EncoderReplacementFallbackBuffer object is called the replacement fallback buffer. The conversion operation encodes the replacement fallback buffer instead of the original input 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