Use bracketless OPC UA node IDs for arrays

tests/ZB.MOM.WW.LmxOpcUa.Tests/Helpers/OpcUaTestClient.cs

@@ -130,6 +130,34 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Helpers
             return Session.ReadValue(nodeId);
         }
 
+        /// <summary>
+        /// Read a specific OPC UA attribute from a node.
+        /// </summary>
+        /// <param name="nodeId">The node whose attribute should be read.</param>
+        /// <param name="attributeId">The OPC UA attribute identifier to read.</param>
+        /// <returns>The attribute value returned by the server.</returns>
+        public DataValue ReadAttribute(NodeId nodeId, uint attributeId)
+        {
+            var nodesToRead = new ReadValueIdCollection
+            {
+                new ReadValueId
+                {
+                    NodeId = nodeId,
+                    AttributeId = attributeId
+                }
+            };
+
+            Session.Read(
+                null,
+                0,
+                TimestampsToReturn.Neither,
+                nodesToRead,
+                out var results,
+                out _);
+
+            return results[0];
+        }
+
         /// <summary>
         /// Write a node's value, optionally using an OPC UA index range for array element writes.
         /// Returns the server status code for the write.