Assembly: System.Management.Automation (in System.Management.Automation.dll)
It is permitted to subclass ConvertThroughString but there is no established scenario for doing this, nor has it been tested. For example, suppose you have a type that has a parsing method that converts only a string to your type. If you want the ConvertTo method to use this converter with your class, you should use the TypeConverterAttribute with ConvertThroughString in your class. This would allow your type to convert integers, doubles, strings and other types.
Although it is possible to derive from this class, there is no established scenario for doing this and any attempt to do so might result in unexpected behavior.