给应用添加图标，完成给设备添加变量表的功能

Helper/DataServicesHelper.cs

@@ -7,6 +7,24 @@ namespace PMSWPF.Helper;
 
 public class DataServicesHelper
 {
+    
+    /// <summary>
+    /// 从设备列表中找到变量表VarTable对象
+    /// </summary>
+    /// <param name="vtableId">VarTable的ID</param>
+    /// <returns>如果找到择返回对象，否则返回null</returns>
+    public static VariableTable FindVarTableForDevice(List<Device> devices, int vtableId)
+    {
+        VariableTable varTable = null;
+        foreach (var device in devices)
+        {
+            varTable = device.VariableTables.FirstOrDefault(v => v.Id == vtableId);
+            if (varTable != null)
+                return varTable;
+        }
+
+        return varTable;
+    }
     public static MenuBean FindMenusForDevice(Device device,List<MenuBean> menus)
     {
         foreach (var mainMenu in menus)
@@ -24,6 +42,23 @@ public class DataServicesHelper
         return null;
     }
     
+    /// <summary>
+    /// 给菜单排序
+    /// </summary>
+    /// <param name="menu"></param>
+    public static void SortMenus(MenuBean menu)
+    {
+        if (menu.Items == null || menu.Items.Count() == 0)
+            return;
+        menu.Items.Sort((a, b) =>
+            a.Type.ToString().Length.CompareTo(b.Type.ToString().Length)
+        );
+        foreach (var menuItem in menu.Items)
+        {
+            SortMenus(menuItem);
+        }
+    }
+    
     public static ViewModelBase GetMainViewModel(string name)
     {
         ViewModelBase navgateVM = App.Current.Services.GetRequiredService<HomeViewModel>();