如何创建通用 Task.ContinueWith 扩展方法

Question

所以目前我有一个 Task.ContinueWith 扩展方法，如下所示：

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);
}

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

我试过：

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

The type or namespace name T could not be found

如何创建通用 Task.ContinueWith 扩展方法？

Answer 1

您在方法名称中缺少 T 声明。另外你的 Action<T> 需要变成 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);
}

如何创建通用 Task.ContinueWith 扩展方法

How to create a generic Task.ContinueWith extension method

c#

generics

task-parallel-library