c# - Nested Async/Await Doesn't Appear To Be Scaling -

i have following (simplified) code:

public async task getdata(domainobject domainobject, int depth) {   // async operation quick, , there's five.   ienumerable<tierone> tierones = await domainobject.gettieronesasync();    var tieronetasks = tierones.select(async tierone =>    {     // async operation quick , there's three.     ienumerable<tiertwo> tiertwos = await tierone.gettiertwosasync();      if (depth <= tiertwodepth)       return;      var tiertwotasks = tiertwos.select(async tiertwo =>      {       // async operation fast, , there's >= 100.       ienumerable<tierthree> tierthrees = await tiertwo.gettierthreesasync();        if (depth <= tierthreedepth)         return;        var tierthreetasks = tierthrees.select(async tierthree =>        {         // async operation slow, , there's usually.. 50?         await tierthree.gettierfoursasync();       });        await task.whenall(tierthreetasks.toarray());     });      await task.whenall(tiertwotasks.toarray());   });    await task.whenall(tieronetasks.toarray()); } 

based off of have seen, not seem scaling well. of async operations "true async" operations meaning i/o.

am using async/await incorrectly scenario? based off of current observations, isn't scaling expect. tpl dataflow solution?

for single call getdata, nested async/await calls won't introduce concurrency. retrieve tierones, tiertwos tierone-#1, tierthrees tiertwo-#1, , on, run in sequence (though there may concurrency inside gettier*async methods).

if want concurrent requests, tpl dataflow indeed better solution.