Impact of optional members on a .Net application

Reading the documentation for Extensible Types, it says that optional members are not supported in the .NET API. What exactly is the resulting behaviour of this? For instance, what happens if a Java application publishes a sample where some optional members are not set and a .NET application is subscribed to that topic? Will it result in a crash? Will the .NET application get null values for the unset fields? Will the publisher/subscriber simply not match?

 Also, what is the behaviour of the rtiddsgen application? Does it ignore the @optional directive when generating for .NET, or does it give an error?

If I'm looking to reduce bandwitdh by only sending a subset of the members, is there an alternative to @optional that would be supported by the .NET API?

Thanks!

Edit: We did some experiments and we stumbled onto an issue with the output of rtiddsgen in Java. Let's say we have the following IDL:

struct SomeStruct{

    long x;

    long long y; //@Optional

}

Then in the generated java code, y is defined as a Long (capital letter so that it's an object that can be null)

In the hashcode method of the generated Java code, it does something like:

int result = 0;

result += (int)x;

if(y != null)

     result += (int)y;

That last line doesn't work though, you can't cast a Long to an int in java. You can cast from long to int, or from Long to long, but not straight Long to int.