Closes the current interchange by writing its footer segment.
The CreateInterchangeFooter method will write any existing segments to the output stream and then generate and write the interchange closing segment (IEA or UNZ). If there is an open transaction set, CreateInterchangeFooter will first call CreateTransactionFooter to close it. If there is an open functional group, CreateInterchangeFooter will first call CreateFunctionalGroupFooter to close it. If there is no interchange open, an exception will be thrown.
This method returns a result code; 0 indicates success, while a non-zero error code indicates that this method encountered an error during its execution. If an error occurs, the GetLastError() method can be called to retrieve the associated error message. (Note: This method's result code can also be obtained by calling the GetLastErrorCode() method after it returns.)