Question

我有以下功能，我想在完成后取消订阅RunWorkerCompleted（以防止内存泄漏）。但是我得到了错误＆＃34;使用未分配的本地变量＆＃39; runWorkerCompleted＆＃39;＆＃34;

private void Assign<T>(Func<object> method, Action<T> setter)
{
    ShowLoadingLabel();
    var bw = new BackgroundWorker();
    DoWorkEventHandler doWork = (object sender, DoWorkEventArgs e) => e.Result = ((Func<object>)(e.Argument))();
    bw.DoWork += doWork;
    RunWorkerCompletedEventHandler runWorkerCompleted = (object sender, RunWorkerCompletedEventArgs e) =>
    {
        setter((T)e.Result);
        HideLoadingLabel();
        bw.DoWork -= doWork;
        bw.RunWorkerCompleted -= runWorkerCompleted; // Error
    };
    bw.RunWorkerCompleted += runWorkerCompleted;
    bw.RunWorkerAsync(method);
}

如何取消订阅？

Answer 1

要使处理程序自行删除，您需要遵循以下通用模板：

DelegateType handler = null;

handler = ()=>
{
    DoOtherStuff();
    someObject.SomeEvent -= handler;
};

someObject.SomeEvent += handler;

Answer 2

你不能在同一行中分配和使用（技术上仍然是初始化行。只需将你的行分成两行。

private void Assign<T>(Func<object> method, Action<T> setter)
{
    ShowLoadingLabel();
    var bw = new BackgroundWorker();
    DoWorkEventHandler doWork = (object sender, DoWorkEventArgs e) => e.Result = ((Func<object>)(e.Argument))();
    bw.DoWork += doWork;
    RunWorkerCompletedEventHandler runWorkerCompleted = null;
    runWorkerCompleted = (object sender, RunWorkerCompletedEventArgs e) =>
    {
        setter((T)e.Result);
        HideLoadingLabel();
        bw.DoWork -= doWork;
        bw.RunWorkerCompleted -= runWorkerCompleted; // Error
    };
    bw.RunWorkerCompleted += runWorkerCompleted;
    bw.RunWorkerAsync(method);

但是我认为所有这些都是unessesary，因为bw超出了函数末尾的范围，因此没有任何东西支持你的委托，所以没有内存泄漏。

Answer 3

您获得的错误是＆＃34;用于未分配的本地变量＆＃34;要解决此问题，请将runworkerCompleted初始化为null，然后为其指定一个值，如：

RunWorkerCompletedEventHandler runWorkerCompleted = null;
runWorkerCompleted = (object sender, RunWorkerCompletedEventArgs e) =>
{
    setter((T)e.Result);
    HideLoadingLabel();
    bw.DoWork -= doWork;
    bw.RunWorkerCompleted -= runWorkerCompleted; // Error
};

取消订阅RunWorkerCompleted？

3 个答案: