IIOP.Net bring IIOP support to .Net, allowing .Net code to invoke any IIOP object. Thus you can write Java RMI, expose it in ORBD, and .Net will be able to invoke it.
Don’t catch NullPointerException. Check for it.
String concatenation to create a hash key or to store multiple values is easy but fragile. Prefer an object key with a proper hashcode. Prefer an object to store multiple values. Otherwise use a standard such as CSV instead of using your own “dash-separated values”. Use a library to handle escaping problems (a name may also contain a comma).
If you do need to concat Strings, use StringBuilder/StringBuffer. Know the difference between the two.