In this https://stackoverflow.com/a/12867132/171121回应,我想出了以下辅助方法,可以被不同的人重用Task
创建者将事件转换为任务完成源。
// Helper method
static Task<T> TaskFromEventHelper<T>(object target, string eventName, Func<TaskCompletionSource<T>, object> resultSetterFactory) {
var tcs = new TaskCompletionSource<T>();
var addMethod = target.GetType().GetEvent(eventName).GetAddMethod();
var delegateType = addMethod.GetParameters()[0].ParameterType;
var d = Delegate.CreateDelegate(delegateType, resultSetterFactory(tcs), "Invoke");
addMethod.Invoke(target, new object[] {d});
return tcs.Task;
}
// Empty events (Action style)
static Task TaskFromEvent(object target, string eventName) {
return TaskFromEventHelper(target, eventName, (Func<TaskCompletionSource<object>, object>)(tcs => (Action)(() => tcs.SetResult(null))));
}
// One-value events (Action<T> style)
static Task<T> TaskFromEvent<T>(object target, string eventName) {
return TaskFromEventHelper(target, eventName, (Func<TaskCompletionSource<T>, object>)(tcs => (Action<T>)(tcs.SetResult)));
}
// Two-value events (Action<T1, T2> or EventHandler style)
static Task<Tuple<T1, T2>> TaskFromEvent<T1, T2>(object target, string eventName) {
return TaskFromEventHelper(target, eventName, (Func<TaskCompletionSource<Tuple<T1, T2>>, object>)(tcs => (Action<T1, T2>)((t1, t2) => tcs.SetResult(Tuple.Create(t1, t2)))));
}
在我给出的使用辅助方法的三个示例中,每个示例都有一个tcs.SetResult
组件,这让我认为也有一种方法可以将其移动到辅助方法中,这可能会简化签名,这样辅助方法可能只需要接受Func<?, T>
,其中Func
将采取的输出event
并将其转换为任何内容tcs.SetResult
需要。
即,我认为必须有一种方法来创建一个助手,这样我就可以将其写为
// Empty events (Action style)
static Task TaskFromEvent(object target, string eventName) {
return TaskFromEventHelper<object>(target, eventName, new Func<object>(() => null));
}
// One-value events (Action<T> style)
static Task<T> TaskFromEvent<T>(object target, string eventName) {
return TaskFromEventHelper<T>(target, eventName, new Func<T, T>(t => t));
}
// Two-value events (Action<T1, T2> or EventHandler style)
static Task<Tuple<T1, T2>> TaskFromEvent<T1, T2>(object target, string eventName) {
return TaskFromEventHelper<Tuple<T1, T2>>(target, eventName, new Func<T1, T2, Tuple<T1, T2>>(Tuple.Create));
}
,但这就是为什么我不知道?
in Func<?, T>
多于。例如这个需要?
to be two参数。是否可以传入为object
不知何故?我有一种感觉,这是可能的,但如果是这样,它需要一些真正的反射魔法。