c# - 静态变量在一段时间后重置为 null

Question

我有一个 static 成员，它是一个列表，它似乎有时会由于某种原因(可能是在未捕获的异常之后)重置为 null。这是我的代码:

public abstract partial class MyClass
{
            private static List<MyClass> Types;

            static MyClass()
            {
                Types = new List<MyClass>();
                Types.Add(new Myclass(0));
                Types.Add(new Myclass(1));
            }


            public static MyClass GetMyClass(int id)
            {                
                return Types.Single(x => x.id == id);
            }
}

GetMyClass 方法将触发一个null 引用异常。在我的代码中，我没有将此成员设置为 null。你有想法吗？

如果有帮助的话，这里是完整的代码:

public partial class TestRequest
{
    public abstract partial class TrType
    {
        private static List<TrType> Types;

        static TrType()
        {
            Types = new List<TrType>();
            Types.Add(TrType.Real.Instance);
            Types.Add(TrType.Template.Instance);
        }
        protected int idTrType;

        public static TrType GetTrType(int id)
        {
            return Types.Single(x => x.idTrType == id);
        }

        public int IdTrType
        {
            get { return idTrType; }
            set { idTrType = value; }
        }

        public abstract void Launch(TestRequest tr);
    }
}

// In another file.

public partial class TestRequest
{
    public partial class TrType
    {
        public class Real : TestRequest.TrType
        {
            private static Real instance;
            public const int ID = 1;

            protected Real()
            {
                idTrType = ID;
            }

            static Real()
            {
                instance = new Real();
            }

            public static Real Instance
            {
                get { return instance; }
                set { instance = value; }
            }

            public override void Launch(TestRequest tr)
            {
                // do something
            }
        }
    }
}

Answer 1

我相信您会因为 Single 而遇到异常. (这不是 NRE)

The Single(IEnumerable) method throws an exception if the input sequence is empty. To instead return null when the input sequence is empty, use SingleOrDefault.

尝试:

 return Types.SingleOrDefault(x => x.id == id);

如果没有找到，将返回 null。但是如果针对 id

找到多个项目，您仍然会得到一个异常