Question

我是reading about C# events and delegates，我想将以下代码复制并粘贴到LINQPad中并运行它：

class Test
{
    public event EventHandler MyEvent
    {
        add
        {
            Console.WriteLine ("add operation");
        }

        remove
        {
            Console.WriteLine ("remove operation");
        }
    }

    static void Main()
    {
        Test t = new Test();

        t.MyEvent += new EventHandler (t.DoNothing);
        t.MyEvent -= null;
    }

    void DoNothing (object sender, EventArgs e)
    {
    }
}

我正在查询属性中导入System命名空间。

我无法弄清楚为什么LINQPad抛出NullReferenceException：

Message Object reference not set to an instance of an object.
Data    Data
InnerException  (null)
TargetSite  TargetSite
StackTrace     at LINQPad.ExecutionModel.ClrQueryRunner.Run()
   at LINQPad.ExecutionModel.Server.RunQuery(QueryRunner runner)
HelpLink    null
Source  LINQPad
HResult -2147467261

如果我在Visual Studio中创建一个项目，那么相同的代码编译就好了，这是我想要避免的。

Answer 1

您需要将主要方法移出类，如下所示：

void Main()
{
    Test t = new Test();

    t.MyEvent += new EventHandler (t.DoNothing);
    t.MyEvent -= null;
}

class Test
{
    public event EventHandler MyEvent
    {
        add
        {
            Console.WriteLine ("add operation");
        }

        remove
        {
            Console.WriteLine ("remove operation");
        }
    }

    public void DoNothing (object sender, EventArgs e)
    {
    }
}

这是LinqPad的限制。

干杯

LINQPad在有效代码上抛出NullReferenceException

1 个答案: