Question

I m currently working on a VariableWatcher class in C#.
What I want to do, is to raise a event every time a variable is changed to a specific value.
For example: I have a bool a , which is false. I pass it to the VariableWatcher class thogether with the value on which the event should be raised, true.
I already made an approach to the solution of this problem, but I obviously misunderstood some point about boxing/unboxing.

这是我的法典:

  public class ValueWatch
  {
    public delegate void ValueTriggeredD(string ID, string valuename, object source);
    public event ValueTriggeredD ValueTriggered;

    Dictionary<string, object[]> LookUp = new Dictionary<string, object[]>(); //Key = ID, Value[0] = PropertyName, Value[1] = ObjTrigger, Value[2] = ObjWatch
    Timer ttt;

    public void Initialize()
    {
        ttt = new Timer(new TimerCallback(CB_T), null, 0, 50);  
    }
    void CB_T(object o)
    {
        if (LookUp.Count > 0)
        {
            foreach (KeyValuePair<string, object[]> kvp in LookUp)
            {
                Type tp = kvp.Value[2].GetType();
                FieldInfo inf = tp.GetField((string)kvp.Value[0]);
                if (inf != null)
                {
                    object curval = inf.GetValue(kvp.Value[2]);
                    if (curval == kvp.Value[1])
                    {
                        if (ValueTriggered != null)
                            ValueTriggered(kvp.Key, (string)kvp.Value[0], kvp.Value[2]);
                    }
                }
            }
        }
    }
    public void StartWatching(string ID, object ListObj, object ValueForTrigger, string PropertyName)
    {
        if (LookUp.ContainsKey(ID))
            System.Diagnostics.Debug.Print("already there");
        else
        {
            LookUp.Add(ID, new object[] { PropertyName, ValueForTrigger, ListObj });
        }
    }
    public void StopWatching(string ID)
    {
        LookUp.Remove(ID);
    }
}

我的问题是:在我改变价值时,为什么储存在数值中的物体不会改变?

例:

bool b = false;
valueWatch.ValueTriggered += new ValueTriggeredD(this.VT);
valueWatch.StartWatching("ID1", this, true, "b");
...
b = true;
...
void VT(string ID, string VN, object Source)
{
    //Never triggered
}

Answer 1

这一权利。它永远不会触发。当你打上贵重的盒子时,你实际上复制了价值,并把它放在记忆中。因此,当你改变变数价值时,你并没有改变盒式价值。第一点是想到的——利用不安全的环境来打上可变地址,但不幸的是。 NET不支持点击器(,自MSDN ):

点数类型不从物体继承,在点数类型和物体之间不存在换算。此外,箱子和箱子不支持点子。然而,您可以转换不同点类型和点距类型和整体类型。

因此,你的唯一可能途径——利用不安全的环境,储存<条码>中的所有变数地址* :

        unsafe
        {
            bool test = false;
            bool* adr = &test;

            void* testObj = adr;
            test = true;
            Console.WriteLine("native test s value is" + test.ToString());
            Console.WriteLine("unboxed test s value is" + (*((bool*)testObj)).ToString());
        }

但是,正如在评论中提到的,为什么不执行在财产发生变化时会引发的事件?

Answer 2

我最后指出:

我在标的上设定了数值,而不是将其放在标的上。 www.un.org/chinese/ga/president

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