Making a class Async for WinRT / Windows 8 Developement - asynchronous

Question

I'm developing a Win 8 app which needs to do some possibly long running looping and calculations based around the data input by the user. This calculation is run often to update the results in real time.
The calculations are done by a calculator class. I will use example code to give an idea
public class ResultCalculator
{
List<Data> Input1 = new List<Data>();
IQueryable<int> Input2;
IQueryable<Data2> Input3;
public ResultCalculator(List<int> items1, List<Data2> items2)
{
items1.Sort((x,y) => y.CompareTo(x));
Input2 = items1.AsQueryable();
Input3 = items2.AsQueryable().OrderByDescending(w => w.LValue);
}
public void CalculateLValues()
{
foreach (var v in Input3)
{
for (int i = 1; i <= v.Quantity; i++)
{
if (Input1.Count > 0)
{
Data existing = FindExisting(v.LValue, 4);
if (existing != null)
{
existing.Add(v.LValue);
}
else
{
FindNew(v.LValue);
}
}
else
{
FindNew(v.LValue);
}
}
}
OptimisePass1();
}
public void FindNew(int LValue)
{
int options = FindNewItem(LValue, 0);
if (options != 0)
{
Data newdata = new Data(options);
newdata.Add(LValue);
Input1.Add(newdata);
}
}
public void OptimisePass1()
{
foreach (var w in Input1)
{
var ShorterLValues = from sl in Input2 where sl < w.LValue orderby sl select sl;
foreach (var sl in ShorterLValues)
{
if (sl > w.LValue - w.Remaining)
{
w.LValue = sl;
w.CalculateRemaining();
}
}
// MORE CALCULATION TO DO IN ANOTHER LOOP
}
}
public Data FindExisting(int LValueRequired, int additionalvalue)
{
Input1.OrderBy(w => w.LValue);
foreach (var sl in Input1.Where(i => i.Remaining > 0).OrderBy(i => i.Remaining))
{
if (sl.Remaining >= LValueRequired + additionalvalue)
{
return sl;
}
}
return null;
}
public int FindNewItem(int LValueRequired)
{
foreach (var sl in Input2)
{
if (sl >= LValueRequired + 4)
{
return sl;
}
}
return 0;
}
}
This class is the used from my ViewModel as below...
public async Task UpdateCalculationAsync()
{
var data1 = new List<int>(sInput);
var reqlist = new List<Data2>(sInput2);
var lc = new ResultCalculator(data1, data2);
NL.Clear();
await Task.Run(() => lc.CalculateLValues());
foreach (var i in lc.Data1)
{
NL.Add(i);
}
}
Without any async use this held up the UI when it ran if there were many items in the lists. So I added the "await Task.Run(() => lc.CalculateLValues())" to make it run async. I've got a basic grasp of async but not really understood how to properly make my classes run in async. Is this approach correct?
I believe that what I've done hands off the calculation to the background thread. Certainly the UI now remains responsive and can be used whilst the calculation is running. Once the result is calculated my viewmodel gets the result and the UI updates. What I'd really rather have is for my ResultCalculator class to have Task returning methods which I can await. However I'm really struggling on how to refactor for that. I'm not even sure there's a need if this works and is a valid approach. But I'm not 100% convinced it is the proper use of the async pattern and wanted to check if it can be improved?

Answer 1

suggest to do something like this:
// user will do some action on the UI to trigger the compute
public async Task Button1_Click(..)
{
await this.ViewModel.RecalculateAsync();
}
class ViewModel
{
public async Task RecalculateAsync()
{
var data1 = new List<int>(sInput);
var reqlist = new List<Data2>(sInput2);
var lc = new ResultCalculator(data1, data2);
await Task.Run(() => lc.CalculateLValues());
// I am not sure that is NL - if it is items like property on viewmodel that is bound to ListView like control in xaml - that should be fine.
// otherwise, add code here to add the list of result items to an observable collection
// expose this collection as Items property on viewmodel and bind in xaml to ListView.ItemsSource
}
}