Assembly: BioSharp.Core (in BioSharp.Core.dll) Version: 0.1.3191.26120 (0.1.0.0)
public class IllegalAlphabetException : BioException
The usual reason for throwing an IllegalAlphabetException is that you are trying to parse an ISymbolList into a method that only works for some alphabets, but not for the alphabet associated with that ISymbolList.
Original BioJava version by Matthew Pocock. Port to C# by Doug Swisher.