在运行时访问对象数组 - System.NullReferenceException

Question

我是 C# 新手，我的编码有问题。我在运行时遇到错误。似乎没有分配对象数组。欢迎任何帮助/提示。我有一个带有修理室的“建筑”类。预计不会改变或增加房间。房间有很多属性。在我的“Home”类中，我想通过对象数组访问所有房间以及特定房间。提前致谢：Class Home{private void StartProgramm()        {            //get all Objects of class "Building"            Building[] building = Building.Buildings;            //System.NullReferenceException during runtime            set_label_header(building[0].Name);            //Access to room1            Building room1 = Building.room1;            set_label_header(room1.Name);            //Get room2            Building room2 = Building.GetBuilding("room2");            set_label_header(room2?.Name);         }}    class Building    {        public string Name { get; set; }        public ArrayList tool_groupList = new ArrayList();        public ArrayList pos_List = new ArrayList();        public ArrayList inv_list = new ArrayList();        public static Building room1;        public static Building room2;        public static Building[] Buildings;    public Building()            {            //create room 1 and add some attributes            room1 = new Building { Name = "room1" };            room1.tool_groupList.Add(1);            room1.tool_groupList.Add(2);            room1.pos_List.Add(14);            room1.pos_List.Add(15);            room1.pos_List.Add(16);            room1.pos_List.Add(17);            Iventory[] inventories = Inventory.get_inventories();            room1.areaList.AddRange(inventories);        }

Answer 1

您试图在调用Building.Buildings类的构造函数之前访问静态字段Building。创建实例后，Building静态字段将被分配。您可能想使用静态构造函数，如下例所示：

static Building()
{
    ...
    Buildings = new Building[] { room1, room2 };
}