Yes, the event args are big, and it is usually enough to transfer just parts of it. In fact, all its parts are serializable/deserializable in the same way as described for the whole event args, if you wanted to use that way.

Yes, properties like HasGoodStatus, HasBadStatus, HasValue are read-only. This is because they are just conditions made on top of other parts UAAttributeData - specifically, the StatusCode. I suggest that instead of trying to transfer there, you simply transfer the StatusCode. It is read/write, so you can restore it afterwards, and at the same time, the HasGoodStatus etc. properties will be restored automatically.

The StatusCode itself is of UAStatusCode type, but that's just a convenience wrapper over a 32-bit unsigned integer. So what you actually end up transferring would be the StatusCode.InternalValue.

One final gotcha: The InternalValue mentioned above is actually declared as 64-bit signed integer. This is because some languages (such as VB, VB.NET) cannot handle 32-bit unsigned integers. Therefore the property is declared wider, but it never contains a value outside of 32-bit unsigned integer range, and you can safely transfer just the low 32 bits and/or convert it to unsigned 32-bit integer.

If this was in .NET, the answer would be relatively easy: Most our objects, including EasyUADataChangeNotificationEventArgs, support [Serializable]/ISerializable, and can therefore be easily stored into a binary stream or retrieved from it.

It was not really our design goal to also support serialization for COM languages and tools, but (depending on the language), it might be possible to achieve that (but we have never tried so far, I admit).

The general steps for serialization should roughly be:

1. Create an instance of .NET MemoryStream, using CoMemoryStream.Create.
2. Create an instance of .NET BinaryFormatter, using CoBinaryFormatter.Create.
3. Call binaryFormatter.Serialize, passing it the memoryStream, and the easyUADataChangeNotificationEventArgs.
4. Call memoryStream.GetBuffer or memoryStream.Read to obtain the array of bytes.

The general steps for deserialization should roughly be:

1. Create an instance of .NET MemoryStream, using CoMemoryStream.Create.
2. Call memoryStream.Write with the array of bytes.
3. Create an instance of .NET BinaryFormatter, using CoBinaryFormatter.Create.
4. Call binaryFormatter.Deserialize, passing it the memoryStream.
5. Cast the resulting value to _EasyUADataChangeNotificationEventArgs

Let me know if you run into problems with this.

Regards