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 );

}

}

}

}