true if the replacement string is not empty; false if the replacement string is empty.
The erload:System.Text.Encoding.GetBytes and erload:System.Text.Encoder.Convert methods call EncoderReplacementFallbackBuffer.Fallback(char, int) if they encounter an unknown character in their input. If the return value of EncoderReplacementFallbackBuffer.Fallback(char, int) is true, the calling method can invoke the EncoderReplacementFallbackBuffer.GetNextChar method to obtain each character in the replacement fallback buffer.