.NET 4.0中SynchronizationContext.Current为null的问题的解决方法 [英] Workaround for issue in .NET 4.0 where SynchronizationContext.Current is null

问题描述

.NET 4.0主线程上 SynchronizationContext.Current 意外为空的问题的解决方法是什么？请参阅：

What is a workaround for the issue where the SynchronizationContext.Current is null unexpectedly on the main thread in .NET 4.0? See:

• SynchronizationContext.Current在主UI线程上的Continuation中为null

• SynchronizationContext.Current is null in Continuation on the main UI thread

推荐答案

我创建了几种扩展方法，它们与 ContinueWith 和 StartNew ，除了它们还需要另外的 SyncronizationContext 。然后，在执行操作之前，我使用此参数恢复预期的 SynchronizationContext ：

I created several extension methods that matched ContinueWith and StartNew except that they also take an additional SyncronizationContext. I then use this argument to restore the expected SynchronizationContext before executing the action:

下面，我给出了示例：

public static class TaskExtensionMethods
{
    public static Task ContinueWith_UsingSyncContextWorkaround(this Task task, Action<Task> continuationAction, CancellationToken cancellationToken, TaskContinuationOptions continuationOptions, TaskScheduler scheduler, SynchronizationContext sc)
    {
        Action<Task> actionWithWorkaround = t =>
        {
            SynchronizationContext.SetSynchronizationContext(sc);
            continuationAction(t);
        };

        return task.ContinueWith(actionWithWorkaround, cancellationToken, continuationOptions, scheduler);
    }

    public static Task StartNew_UsingSyncContextWorkaround(this TaskFactory taskFactory, Action action, CancellationToken cancellationToken, TaskCreationOptions creationOptions, TaskScheduler scheduler, SynchronizationContext sc)
    {
        Action actionWithWorkaround = () =>
        {
            SynchronizationContext.SetSynchronizationContext(sc);
            action();
        };

        return taskFactory.StartNew(actionWithWorkaround, cancellationToken, creationOptions, scheduler);
    }
}

然后我使用这些扩展方法代替 .ContinueWith 或 .StartNew

I then use these extension methods in place of .ContinueWith or .StartNew

相关问题：

• 如何创建通用Task.ContinueWith扩展方法

• How to create a generic Task.ContinueWith extension method

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