Writing arrays of generic structs

[SachaSaxer]

I'm fairly new to OPC UA so I might be going about this completely the wrong way. I have to write generic data that is not known at compile time to a SPS. So far I managed to write all simple data types as well as arrays of simple type and single structs. I can't seem to find a way to get the necessary data to create a WriteValue for an array of structs, though.

For structs I'm converting the data to a byte array and get the StructureDefinition from the node to create and ExtensionObject to use for the WriteValue.

My code looks like this:

            var nodeId = GetNodeId(path);
            Dictionary<uint, DataValue> nodeAttributes = ReadNodeAttributes(nodeId.ToString());
            DataTypeNode dataTypeNode = (DataTypeNode)ReadNode(nodeAttributes[Attributes.DataType].ToString());

            //Get the structure definition
            StructureDefinition structureDefinition = (StructureDefinition)dataTypeNode.DataTypeDefinition.Body;
            ExtensionObject ExtensionObject = new ExtensionObject();
            ExtensionObject.TypeId = structureDefinition.DefaultEncodingId;
            ExtensionObject.Body = ConvertParameterToByteArray(parameter);
            DataValue dataValue = new DataValue(ExtensionObject);

            //Setup for the WriteValue
            WriteValue writeValue = new WriteValue();
            writeValue.NodeId = nodeId;
            writeValue.Value = dataValue;
            writeValue.AttributeId = Attributes.Value;

The structs can be created dynamically in the software (to match the structure on the SPS). I was hoping to just be able to create a byte array starting with the number of structs, followed by concatenated byte arrays of the structs.

Where am I going wrong?

[SachaSaxer]

OK, I managed to get a step closer to the solution but I still get BadTypeMismatch errors even though the Value of my WriteValue looks exactly like the Value of the ReadValue when I read the array of structs from the PLC.
This is how I create my WriteValue for an array of structs:

ExtensionObject[] values = new ExtensionObject[customTable.Count]; int i = 0; ExpandedNodeId expandedNodeId = new ExpandedNodeId("TE_" + MakeNodeIdentifier(path), "http://wwww.siemens.com/simatic-s7-opcua"); foreach (IStructParameter param in customTable) { values[i] = new ExtensionObject(); values[i].TypeId = expandedNodeId; values[i].Body = ConvertParameterToByteArray(param); i++; } WriteValue writeValue = new WriteValue(); writeValue.NodeId = nodeId; DataValue dataValue = new DataValue(values); writeValue.Value = dataValue; writeValue.AttributeId = Attributes.Value;

I tried to set the data type of the node I write into but TypeId is readonly. Any help would be really appreciated.

[SachaSaxer]

Finally found a way. I'm reading the structure information of the first element and use this to tell the OPC UA server how to interpret the data I send.

`var innerNode = GetNodeId(path+"[0]");
Dictionary<uint, DataValue> nodeAttributes = ReadNodeAttributes(nodeId.ToString());
DataTypeNode dataTypeNode = (DataTypeNode)ReadNode(nodeAttributes[Attributes.DataType].ToString());

                    //Get the structure definition
                    StructureDefinition structureDefinition = (StructureDefinition)dataTypeNode.DataTypeDefinition.Body;

                    ExtensionObject[] values = new ExtensionObject[customTable.Count];
                    int i = 0;
                    foreach (IStructParameter param in customTable)
                    {
                        values[i] = new ExtensionObject();
                        values[i].TypeId = structureDefinition.DefaultEncodingId; ;
                        values[i].Body = ConvertParameterToByteArray(param);
                        i++;
                    }
                    WriteValue writeValue = new WriteValue();
                    writeValue.NodeId = nodeId;
                    DataValue dataValue = new DataValue(values);
                    writeValue.Value = dataValue;
                    writeValue.AttributeId = Attributes.Value;
                    //Add the created value to the collection
                    collection.Add(writeValue);`

I'm sure the code could be written better but at least it works now.