锁定并不prevent InvalidOperationException异常：对象是目前在其他地方使用 [英] Locking does not prevent InvalidOperationException: Object is currently in use elsewhere

问题描述

我是IM pression，根据锁（）将prevent多个线程同时访问一个对象。

I was under the impression that lock() would prevent multiple threads from accessing an object simultaneously.

但是，一个InvalidOperationException（对象是目前在其他地方使用）仍然经常被以下code抛出：

But, an InvalidOperationException (Object is currently in use elsewhere) is still frequently thrown by the following code:

lock (this)
{
    localCopy = (Bitmap)this.bm.Clone();
    int x, y;
    float pX = this.p.x;
    int width = localCopy.Width;
    x = (int)Math.Round((double)(pX * (float)width));
    if (x >= localCopy.Width) x = localCopy.Width - 1;
    y = (int)Math.Round((double)(this.p.y * (float)localCopy.Height));
    if (y >= localCopy.Height) y = localCopy.Height - 1;
    colourPixel = localCopy.GetPixel(x, y);
}

需要注意以下几点：

Some things to note:

• 我分手了的计算X 来的异常的原因隔离。它似乎来自访问该位图。


• 我尝试创建位图的本地副本，但这恰恰会导致相同的异常。我试过克隆（） ING并创建一个新的位图。无论是作品。


• 我试着锁定在这个（如图）和位图对象。无论是作品。

• I split up the calculation of x to isolate the cause of the exception. It appears to come from accessing the bitmap.
• I tried creating a local copy of the bitmap, but this just causes the same exception. I've tried Clone()ing and creating a new Bitmap. Neither works.
• I've tried locking on this (as seen) and on the bitmap object. Neither works.

我是否尝试使用锁（）中的我不应该来的方法？难道我误解了它的目的是什么？我怎样才能prevent 出现InvalidOperationException S'

Am I trying to use lock() in a way I'm not supposed to? Have I misunderstood it's purpose? How can I prevent InvalidOperationExceptions?

推荐答案

我最终得到了这条底线。我搬到了锁入位图属性的getter / setter方法​​，并尽快实现深层复制的方法来释放特性越好。

I eventually got to the bottom of this. I moved the locks into the getter / setter methods of the bitmap property and implemented a "deep copy" method to free up the property as soon as possible.

private static object syncRoot = new Object();
private Bitmap _bm;
private Bitmap bm
{
    get
    {
        lock (syncRoot)
            return this._bm.DeepClone();
    }
    set
    {
        lock (syncRoot)
        {
            this._bm = value.DeepClone();
        }
    }
}

该DeepClone（）扩展方法是从回答另一个问题：

public static T DeepClone<T>(this T a)
{
    using (MemoryStream stream = new MemoryStream())
    {
        BinaryFormatter formatter = new BinaryFormatter();
        formatter.Serialize(stream, a);
        stream.Position = 0;
        return (T)formatter.Deserialize(stream);
    }
}

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