The root exception class. All other runtime exception classes are derived from this.
Many of the classes and methods in the XLL+ run-time libraries throw run-time errors. For example, if an input to a function is of an unexpected type, then an exception of type CXlConversionException is thrown. If you attempt to pass an array back to Excel as the result of an add-in function, and the array is too big to be displayed in Excel, then an exception of type CXlArrayTooLargeException is thrown.
All runtime exception classes are derived from CXlRuntimeException. CXlRuntimeException is itself
derived from the STL standard error type