如何创建一个通用的Task.ContinueWith扩展方法 [英] How to create a generic Task.ContinueWith extension method

问题描述

因此，目前我有一个 Task.ContinueWith 扩展方法，如下所示：

So currently I have a Task.ContinueWith extensions method like so:

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);
}

这个工作正常，但它不能让我访问结果 Task 所以我想创建一个通用的扩展方法。

and this works fine but it doesn't give me access to the result of the Task so I would like to create a generic extension method.

我试过了：

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

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

但这不会编译，因为

But this won't compile because

无法找到类型或名称空间名称

The type or namespace name T could not be found

如何创建一个普通的 Task.ContinueWith 扩展方法？

How do I create a generic Task.ContinueWith extension method?

推荐答案

方法名称中的 T 声明。您还需要 Action< $> 成为 Func< Task< T> ;, T> ：

You're missing the T declaration in the method name. Also you Action<T> needs to become a Func<Task<T>, T>:

public static Task<T> ContinueWithUsingSyncContextWorkaround<T>(this Task<T> task,
                                               Func<Task<T>, T> continuationFunc, 
                                               CancellationToken cancellationToken,
                                               TaskContinuationOptions continuationOptions,
                                               TaskScheduler scheduler,
                                               SynchronizationContext sc)
{
    Func<Task<T>, T> funcWithWorkaround = t =>
    {
        SynchronizationContext.SetSynchronizationContext(sc);
        return continuationFunc(t);
    };

    return task.ContinueWith<T>(funcWithWorkaround, cancellationToken,
                                continuationOptions, scheduler);
}

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