AsyncEnumerableExtensions.cs z

public static class Extensions

{

public static async Task ForEachAsync<T, U>(this IEnumerable<T> collection, Func<T, Task<U>> body, IObserver<U> observer = null)

{

foreach (var item in collection)

{

var res = await body(item);

if (null != observer)

{

observer.OnNext(res);

}

}

}

 

public static async Task ForEachAsyncPerformance<T, U>(this IEnumerable<T> collection, Func<T, Task<U>> body, IObserver<U> observer = null)

{

var enumerator = collection.GetEnumerator();

 

Task<U> task = null;

if (enumerator.MoveNext())

{

task = body(enumerator.Current);

}

while (enumerator.MoveNext())

{

var item = enumerator.Current;

var res = await task;

task = body(item);

if (null != observer)

{

observer.OnNext(res);

}

}

if (null != task)

{

var res = await task;

if (null != observer)

{

observer.OnNext(res);

}

}

}

 

public static async Task ForEachAsync<T, U>(this IEnumerable<T> collection, int parallelism, Func<T, Task<U>> body, IObserver<U> observer = null)

{

int inFlight = 0;

var tasks = new HashSet<Task<U>>();

 

foreach (var item in collection)

{

if (inFlight >= parallelism)

{

var task = await Task.WhenAny(tasks);

tasks.Remove(task);

inFlight--;

if (null != observer)

{

observer.OnNext(task.Result);

}

}

 

inFlight++;

tasks.Add(body(item));

}

 

while (inFlight > 0)

{

var task = await Task.WhenAny(tasks);

tasks.Remove(task);

inFlight--;

if (null != observer)

{

observer.OnNext(task.Result);

}

}

}

}