MapXtreme 操作地图时出现调用目标发生异常的解决方法--地图状态保存

以下代码位于AppStateManager.cs文件中：

// Restore the state
        public override void RestoreState()
        {
            string mapAlias = ParamsDictionary[ActiveMapAliasKey] as string;

            Map map = GetMapObj(mapAlias);
  
            // If it was user's first time and the session was not dirty then save this default state to be applied later.
            // If it was a users's first time and the session was dirtythen apply the default state saved in above step to give users ainitial state.
            if (IsUsersFirstTime())
            {
                if (IsDirtyMapXtremeSession(map))
                {

                    RestoreDefaultState(map);

                }
                else
                {

                    SaveDefaultState(map);

                }
            }
            else
            {
                // If it is not user's first time then restore the last state they saved
                RestoreZoomCenterState(map);

                 //恢复临时图层Animation的状态

                if (HttpContext.Current.Session["Animation" + "Layer"] != null)
               {
                   ManualSerializer.RestoreMapXtremeObjectFromHttpSession("Animation" + "Table");
                   ManualSerializer.RestoreMapXtremeObjectFromHttpSession("Animation" + "Layer");
                }

              //恢复标注图层jcbz的状态

                if (HttpContext.Current.Session["jcbz" + "Layer"] != null)

                            ManualSerializer.RestoreMapXtremeObjectFromHttpSession("jcbz" + "Layer");

                //恢复临时图层Tm的状态

                            if (HttpContext.Current.Session["Tm" + "Layer"] != null)
                {
                    ManualSerializer.RestoreMapXtremeObjectFromHttpSession("Tm" + "Table");
                    ManualSerializer.RestoreMapXtremeObjectFromHttpSession("Tm" + "Layer");
                }

                               // Just by setting it to tempvariables the objects are serialized into session. There is no need toset them explicitly.
                for (int i = 0; i < map.Layers.Count ;i++ )

                       if(map.Layers[i]!=null)                  //必须加这条语句，否则老是在这里出现错误

                           ManualSerializer.RestoreMapXtremeObjectFromHttpSession(map.Layers[i].Name+"Layer");

                      //恢复地图中选中的图元对象

                ManualSerializer.RestoreMapXtremeObjectFromHttpSession("Selection");

            }
        }

        // Save the state
        public override void SaveState()
        {
            string mapAlias = ParamsDictionary[ActiveMapAliasKey] as string;

            Map map = GetMapObj(mapAlias);

            if (map != null)
            {
                SaveZoomCenterState(map);

              //判断地图中是否有Animation图层，有的话保存状态

                if (map.Layers["Animation"] != null)
                {
                   ManualSerializer.SaveMapXtremeObjectIntoHttpSession(MapInfo.Engine.Session.Current.Catalog["Animation"],"Animation" + "Table");
                    ManualSerializer.SaveMapXtremeObjectIntoHttpSession(map.Layers["Animation"], "Animation" + "Layer");
                }

             //判断地图中是否有Tm图层，有的话保存状态

                if (map.Layers["Tm"] != null)
                {
                   ManualSerializer.SaveMapXtremeObjectIntoHttpSession(MapInfo.Engine.Session.Current.Catalog["Tm"],"Tm" + "Table");
                    ManualSerializer.SaveMapXtremeObjectIntoHttpSession(map.Layers["Tm"], "Tm" + "Layer");
                }

               //遍历各图层，有层名为jcbz的层则保存该标注图层的状态

                for (int i = 0; i < map.Layers.Count; i++)

                    if (map.Layers[i].Name == "jcbz")
                    {
                          ManualSerializer.SaveMapXtremeObjectIntoHttpSession(map.Layers[i], "jcbz" + "Layer");
                        break;
                    }

                ManualSerializer.SaveMapXtremeObjectIntoHttpSession(map.Layers, "Layers");

               ManualSerializer.SaveMapXtremeObjectIntoHttpSession(MapInfo.Engine.Session.Current.Selections.DefaultSelection,"Selection");

            }
        }