完成OpcUaService服务

DMS.WPF/ViewModels/Items/OpcUaNodeViewModel.cs

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+using CommunityToolkit.Mvvm.ComponentModel;
+using Opc.Ua;
+using System.Collections.ObjectModel;
+
+namespace DMS.WPF.ViewModels.Items
+{
+    public partial class OpcUaNodeViewModel : ObservableObject
+    {
+        [ObservableProperty]
+        private string _displayName;
+
+        [ObservableProperty]
+        private NodeId _nodeId;
+
+        [ObservableProperty]
+        private NodeType _nodeType;
+
+        [ObservableProperty]
+        private bool _isExpanded;
+
+        [ObservableProperty]
+        private bool _isLoading;
+
+        [ObservableProperty]
+        private bool _isLoaded;
+
+        public ObservableCollection<OpcUaNodeViewModel> Children { get; set; }
+
+        public OpcUaNodeViewModel(string displayName, NodeId nodeId, NodeType nodeType)
+        {
+            DisplayName = displayName;
+            NodeId = nodeId;
+            NodeType = nodeType;
+            Children = new ObservableCollection<OpcUaNodeViewModel>();
+            
+            // 如果是文件夹或对象，添加一个虚拟子节点，用于懒加载
+            if (nodeType == NodeType.Folder || nodeType == NodeType.Object)
+            {
+                Children.Add(new OpcUaNodeViewModel("Loading...", NodeId.Null, NodeType.Folder)); // 虚拟节点
+            }
+        }
+    }
+
+    public enum NodeType
+    {
+        Folder,
+        Object,
+        Variable
+    }
+}