The System.Text.EncoderFallback object represents an error handler that is invoked when a character cannot be converted into an encoded byte sequence. Any one of the following handler types is supported:

• A best-fit fallback handler, which replaces characters that cannot be encoded with some suitable replacement character.

• A replacement fallback handler, which replaces characters that cannot be encoded with some arbitrary replacement character. The .NET Framework includes one replacement fallback handler, System.Text.EncoderFallback, which by default replaces characters that cannot be encoded with a question mark ("?") character.

• An exception fallback handler, which throws an exception when characters cannot be encoded. The .NET Framework includes one exception fallback handler, System.Text.EncoderExceptionFallback, which throws an System.Text.EncoderFallbackException when characters cannot be decoded.