Serialize / deserialize an ExtensionObject or browse nodes better?

[lkomanetz]

I was trying to write a wrapper abstraction around the OPCFoundation.NetStandard.Opc.Ua library. The intent was to simplify the interface a bit. Here is how the interface is meant to work

var connectionStringBuilder = new OpcUaConnectionStringBuilder()
    .WithHostName("127.0.0.1")
    .WithPort(4840)
    .WithOpcConfiguration("/path/to/opc.config.xml")
    .WithListenerInterval(100); // Milliseconds
using var plc = await PlcConnection.OpenAsync(connectionStringBuilder);

// Recursively browses PLC tags and creates a flattened array.  If the NodeClass is an object I browse that object until I find variables
var allTags = plc.GetPlcTags(); // This is cached by the way
var tagToRead = allTags.Single(t => t.Name.EndsWith("MyNumber"));
var result = await plc.ReadAsync<int>(tagToRead); // Tag is an Int32 so I want it returned as an int
await plc.WriteAsync(tagtoRead, 5); // Writing an Int32 value of 5 to the tag we just read from.

There is also a way to make subscribing to tag changes as well but that's no concern right now. Everything has been great until I came across a PLC program that uses nested variable tags. Up until now Variable nodes have stored a single value (whether an array, string, number, or boolean). I didn't even realize you could nest variable nodes inside of a variable node. I always thought that was what object nodes were for.

In something like UA-Expert I would see

• Path (Object)
  • To (Variable)
    • MyNumber (Variable)
    • MyOtherVariable
      • MyBoolean
    • MyString (Variable)

When getting the list of PLC tags my wrapper gets to To and goes "okay...that's a leaf in this tree branch" and doesn't keep going. If I try and go through all of the tags it takes ~13 minutes. I could try to deserialize the ExtensionObject into something like ExpandoObject so I could do something like

var result = await plc.ReadAsync<dynamic>(plc.GetPlcTags().Single(t => t.Name.EndsWith("Path/To")));
Console.WriteLine(result.MyNumber);
Console.WriteLine(result.MyOtherVariable.MyBoolean);

but I've been very unsuccessful in that. I'm not really sure what I should do and could use some guidance.

[lkomanetz]

So deserializing the ExtensionObject into an ExpandoObject does work. Now the question deals with serializing it back to the ExtensionObject. Is there any documentation on how to create an ExtensionObject?

[lkomanetz]

The only thing I need to figure out now, if anyone knows how, is to get the type information that I need to provide to ExtensionObject when I write the byte[] to the Body property. The only one that seems to work is the TypeId from the DataValue that is returned when I read the node. The only way I've gotten it to work is to make sure I read the extension object first, modify it, and then write it to the tag again. I'd like to get that information when I browse the tags. Unfortunately the values I get about type ID or reference type ID don't work.

Anybody know what I can do?