Bubbling events from child to parent (overal progress)

Bubbling events from child to parent (overal progress) - c#

I have a problem which i don't know how to solve.
I have some classes (Processors) that fires an event with progress information ( Percentage of how far it is). There are multiple processors that do this and the top Processor (Engine) which calls them all needs to send information to the end user on its progress.
If i don't know beforehand how many items will be processed by each processor how can i give the user some good feedback on how far the process is?
Take a look at the following simplified example
NetFiddle
class Program {
static void Main(string[] args) {
var p = new Program();
p.Run();
}
private void Run() {
var engine = new Engine();
engine.UpdateProgress += Engine_UpdateProgress;
engine.Process();
Console.ReadLine();
}
private void Engine_UpdateProgress(object sender, UpdateProgressEventArgs e) {
Console.WriteLine($"{e.UpdateDateTime} - Caller: {e.Caller}, Percentage: {e.Percentage}");
}
}
public class Engine {
private readonly ProcessorA _processorA;
private readonly ProcessorB _processorB;
private readonly ProcessorC _processorC;
private readonly ProcessorD _processorD;
public event EventHandler<UpdateProgressEventArgs> UpdateProgress;
public Engine() {
_processorA = new ProcessorA();
_processorB = new ProcessorB();
_processorC = new ProcessorC();
_processorD = new ProcessorD();
//Handle events
_processorA.UpdateProgress += ProcessorA_UpdateProgress;
_processorB.UpdateProgress += ProcessorA_UpdateProgress;
_processorC.UpdateProgress += ProcessorA_UpdateProgress;
_processorD.UpdateProgress += ProcessorA_UpdateProgress;
}
private void ProcessorA_UpdateProgress(object sender, UpdateProgressEventArgs e) {
OnUpdateProgress(e);
}
public void Process() {
_processorA.Process();
_processorB.Process();
_processorC.Process();
_processorD.Process();
}
protected virtual void OnUpdateProgress(UpdateProgressEventArgs e) {
UpdateProgress?.Invoke(this, e);
}
}
public class ProcessorA : Processor {
private readonly ProcessorA_A _processorA_A;
public ProcessorA() {
_processorA_A = new ProcessorA_A();
//Handle events
_processorA_A.UpdateProgress += ProcessorA_A_UpdateProgress;
}
public void Process() {
_processorA_A.Process();
}
private void ProcessorA_A_UpdateProgress(object sender, UpdateProgressEventArgs e) {
OnUpdateProgress(e);
}
}
public class ProcessorB : Processor {
public void Process() {
for (int i = 0; i <= 100; i++) {
var args = new UpdateProgressEventArgs() { Caller = nameof(ProcessorB), Percentage = i, UpdateDateTime = DateTime.Now};
//Do some work
Thread.Sleep(r.Next(50,250));
OnUpdateProgress(args);
}
}
}
public class ProcessorC : Processor {
public void Process() {
for (int i = 0; i <= 100; i++) {
var args = new UpdateProgressEventArgs() { Caller = nameof(ProcessorC), Percentage = i, UpdateDateTime = DateTime.Now };
//Do some work
Thread.Sleep(r.Next(50, 250));
OnUpdateProgress(args);
}
}
}
public class ProcessorD : Processor {
public void Process() {
for (int i = 0; i <= 100; i++) {
var args = new UpdateProgressEventArgs() { Caller = nameof(ProcessorD), Percentage = i, UpdateDateTime = DateTime.Now };
//Do some work
Thread.Sleep(r.Next(50, 250));
OnUpdateProgress(args);
}
}
}
public class ProcessorA_A : Processor {
public void Process() {
for (int i = 0; i <= 100; i++) {
var args = new UpdateProgressEventArgs() { Caller = nameof(ProcessorA_A), Percentage = i, UpdateDateTime = DateTime.Now };
//Do some work
Thread.Sleep(r.Next(50, 250));
OnUpdateProgress(args);
}
}
}
public class Processor : IProcessor {
protected Random r = new Random();
public event EventHandler<UpdateProgressEventArgs> UpdateProgress;
protected virtual void OnUpdateProgress(UpdateProgressEventArgs e) {
UpdateProgress?.Invoke(this, e);
}
}
public interface IProcessor {
event EventHandler<UpdateProgressEventArgs> UpdateProgress;
}
public class UpdateProgressEventArgs {
public int Percentage { get; set; }
public string Caller { get; set; }
public DateTime UpdateDateTime { get; set; }
}
Just sending the progress from child to parent won't do the trick obviously. I hope someone can help me find a solution for this. Or if someone has another brilliant solution :)
Thanks in advance

Engine could maintain a private list of "the last completeness" of each process. In a Dictionary more than likely.
if we extend your Engine class to have this.
private Dictionary<IProcessor, int> _lastReportedPercentage = new Dictionary<IProcessor, int>();
and in the constructor where all your child processors are defined, set them all to 0.
public Engine()
{
//your other stuff
_lastReportedPercentage[_processorA] = 0;
_lastReportedPercentage[_processorB] = 0;
_lastReportedPercentage[_processorC] = 0;
_lastReportedPercentage[_processorD] = 0;
}
in your Event handler for the child processes do something like this:
private void ProcessorA_UpdateProgress(object sender, UpdateProgressEventArgs e)
{
_lastReportedPercentage[(IProcessor)sender] = e.Percentage;
var totalCompleteness = (int)Math.Floor(_lastReportedPercentage.Values.Sum() / _lastReportedPercentages.Values.Count);
OnUpdateProgress(new UpdateProgressEventArgs() { Caller = nameof(Engine), Percentage = totalCompleteness, UpdateDateTime = DateTime.Now });
}
You will then be reporting, from your Engine, the total completeness of all tasks.
There are some obvious design flaws to this, but you get the idea. It can be extended for a variable number of Processors if they're loaded from not-the-constructor, etc. but this should give you the desired output you'd want.

I would suggest having each processor keep a count of how many items it has completed, and how many items it has remaining.
This way the engine receives updates whenever an item is completed, as well as when an item is added to the processor.
As in Skintkingle's answer, you would then store the last received update from each processor within the engine.
You can then let the engine decide on the best way to put this information across. Something as simple as total completed / total remaining would work well.

Related

Fill list box from another thread

I'm searching for this for several hours now and was not able to find proper solution. I'm c# beginner.
I have a winforms app with a ListBox and a class that does some work and should run forever on separate thread. I want to push MyDataStruct to ListBox each time its created in WorkerClass.Work.
Later on, several WorkerClass instances should run simultaneously and I will have combobox to pick which instance data to feed to ListBox . Is it better to have WorkerClas return only single MyDataStruct and keep their queue in Form1 class or have a queue in each WorkerClass and exchange the entire queue with Form1 every time it changes?
is my void QueueToLb good way to add queue data to ListBox ?
thank you for your support.
public partial class Form1 : Form
{
Queue<MyDataStruct> qList;
MyDataStruct myDataStruct;
private void RunTask()
{
//how do I make MyLongTask to update either qList or myDataStuct
Task.Run(() =>
{
MyLongTask(0, 1000);
});
}
private void MyLongTask(int low, int high)
{
WorkerClass wc = new WorkerClass();
wc.Work(low,high);
}
private void QueueToLb()
{
//is this good way to update listbox from queue?
List<MyDataStruct> lstMds = qList.Reverse<MyDataStruct>().ToList<MyDataStruct>();
List<string> lstStr = new List<string>();
foreach (MyDataStruct m in lstMds)
{
lstStr.Add(m.ToString());
}
listBox1.DataSource = lstStr;
}
}
public class WorkerClass
{
Queue<MyDataStruct> qList; //not sure if its better to keep the queue here or in Form1
public WorkerClass()
{
qList = new Queue<MyDataStruct>();
}
public void Work(int low, int high) //does some work forever
{
while (true)
{
if (qList.Count > 11) qList.Dequeue();
MyDataStruct mds = new MyDataStruct();
Random random = new Random();
mds.dt = DateTime.Now;
mds.num = random.Next(low, high);
qList.Enqueue(mds);
Thread.Sleep(1000);
}
}
}
public class MyDataStruct
{
public DateTime dt;
public int num;
public override string ToString()
{
StringBuilder s = new StringBuilder();
s.Append(num.ToString());
s.Append(" - ");
s.Append(dt.ToShortDateString());
return s.ToString();
}
}
OK I think I figured how to use BackgroundWorker on this, I'll be happy if someone could verify it is correct
public partial class Form1 : Form
{
Queue<MyDataStruct> qList;
BackgroundWorker bw = new BackgroundWorker();
public Form1()
{
InitializeComponent();
bw.WorkerReportsProgress = true;
bw.DoWork += new DoWorkEventHandler(Bw_DoWork);
bw.ProgressChanged += new ProgressChangedEventHandler(bw_ProgressChanged);
}
private void Form1_Load(object sender, EventArgs e)
{
qList = new Queue<MyDataStruct>(12);
}
private void button1_Click(object sender, EventArgs e)
{
bw.RunWorkerAsync();
}
private void MyLongTask(int low = 0, int high = 1000)
{
WorkerClass wc = new WorkerClass(bw);
wc.Work(low,high);
}
private void BindToLbWithQueue()
{
MyDataStruct mds = new MyDataStruct();
Random random = new Random();
mds.dt = DateTime.Now;
mds.num = random.Next(0, 1000);
qList.Enqueue(mds);
QueueToLb();
}
private void QueueToLb()
{
//is this good way to update listbox from queue?
List<MyDataStruct> lstMds = qList.Reverse<MyDataStruct>().ToList<MyDataStruct>();
List<string> lstStr = new List<string>();
foreach (MyDataStruct m in lstMds)
{
lstStr.Add(m.ToString());
}
listBox1.DataSource = lstStr;
}
#region worker
private void Bw_DoWork(object sender, DoWorkEventArgs e)
{
MyLongTask();
}
private void bw_ProgressChanged(object sender, ProgressChangedEventArgs e)
{
qList = (Queue<MyDataStruct>)e.UserState;
QueueToLb();
}
#endregion
}
public class WorkerClass
{
Queue<MyDataStruct> qList; //not sure if its better to keep the queue here or in Form1
BackgroundWorker bw = null;
public WorkerClass(BackgroundWorker bw)
{
this.bw = bw;
qList = new Queue<MyDataStruct>();
}
public void Work(int low, int high) //does some work forever
{
while (true)
{
if (qList.Count > 11) qList.Dequeue();
MyDataStruct mds = new MyDataStruct();
Random random = new Random();
mds.dt = DateTime.Now;
mds.num = random.Next(low, high);
qList.Enqueue(mds);
bw.ReportProgress(0, qList);
Thread.Sleep(1000);
}
}
}
public class MyDataStruct
{
public DateTime dt;
public int num;
public override string ToString()
{
StringBuilder s = new StringBuilder();
s.Append(num.ToString());
s.Append(" - ");
s.Append(dt.ToShortDateString());
return s.ToString();
}
}

Create instance of unknown type

I have class that draw three types of charts, and i want to update it by function public void GetData(PlotModel PlotModel). The main problem is that every series (AreaSeries,CandleStickSeries,HighLowSeries) has different interfaces. How can i update different types in function public void GetData(PlotModel PlotModel). What should i use Activator? Generic?
I think that something like is bad idea:
public void GetData(PlotModel PlotModel) {
while(true) {
System.Threading.Thread.Sleep(1000);
// Add new Item?
switch(PlotModel.Series.First().ToString()) {
case "OxyPlot.Series.AreaSeries":
Console.WriteLine("AreaSeries");
break;
case "OxyPlot.Series.CandleStickSeries":
Console.WriteLine("CandleStickSeries");
break;
case "OxyPlot.Series.HighLowSeries":
Console.WriteLine("HighLowSeries");
break;
}
}
}
Code:
namespace WpfApplication20 {
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
///
public partial class MainWindow : Window {
public MainWindow() {
InitializeComponent();
DataContext = new PlotClass();
}
}
public class PlotClass {
public PlotModel PlotModel { get; set; }
public PlotClass() {
PlotModel = new PlotModel();
DrawCandleChart(PlotModel);
UpdateChartAsync(PlotModel);
}
public void DrawSimpleChart(PlotModel PlotModel) {
Random rnd = new Random();
LineSeries LS = new LineSeries();
for (int i=0;i<10;i++) {
LS.Points.Add(new DataPoint(i,rnd.NextDouble()));
}
PlotModel.Series.Add(LS);
PlotModel.InvalidatePlot(false);
}
public void DrawCandleChart(PlotModel PlotModel) {
Random rnd = new Random();
CandleStickSeries CSS = new CandleStickSeries();
for (int i=0;i<10;i++) {
CSS.Items.Add(new HighLowItem { Close = rnd.NextDouble(), High = rnd.NextDouble(), Low = rnd.NextDouble(), Open = rnd.NextDouble(), X = i });
}
PlotModel.Series.Add(CSS);
PlotModel.InvalidatePlot(false);
}
public void DrawHighLowChart(PlotModel PlotModel) {
Random rnd = new Random();
HighLowSeries HLS = new HighLowSeries();
for (int i = 0; i < 10; i++) {
HLS.Items.Add(new HighLowItem { Close = rnd.NextDouble(), High = rnd.NextDouble(), Low = rnd.NextDouble(), Open = rnd.NextDouble(), X = i });
}
PlotModel.Series.Add(HLS);
PlotModel.InvalidatePlot(false);
}
public void UpdateChartAsync(PlotModel PlotModel) {
Action<PlotModel> Update = new Action<PlotModel>(GetData);
IAsyncResult result = Update.BeginInvoke(PlotModel, null, null);
}
public void GetData(PlotModel PlotModel) {
while(true) {
System.Threading.Thread.Sleep(1000);
// Add new Item?
}
}
}
}

C# 4 and up offers a nice way of processing situations like this: use cast to dynamic, and call a method with one overload per subtype, like this:
private void Process(AreaSeries arSer) {
...
}
private void Process(CandleStickSeries csSer) {
...
}
private void Process(HighLowSeries hlSer) {
...
}
...
while(true) {
System.Threading.Thread.Sleep(1000);
Process((dynamic)PlotModel.Series.First());
// ^^^^^^^^^
}
The cast to dynamic makes the "magic" happen: C# will examine the run-time type of PlotModel.Series.First(), and dispatch to one of the three Process methods that you supplied.
There is a danger in this approach: if PlotModel.Series.First() happens to not match any of the overloads, you get a run-time exception. The compiler cannot perform static analysis to tell you that your call would not succeed. Consider adding a catch-all method for the common superclass of your plots, too, so that you could handle unexpected sub-types more gracefully.

Task and don't close until base task has children

I have class (ConsoleApplication) names ClassA with a field:
public class ClassA
{
List<Task> Tasks;
(...)
public void PlotGrid()
{
Action<object> action = new Action<object>(ShowChart);
Task task = new Task(action, intervalX);
task.Start();
Tasks.Add(task);
}
(...)
private void ShowChart(object intervalX)
{
int interval = Convert.ToInt32(intervalX);
ChartForm chart = new ChartForm(GetValuesForPlotting(), interval);
chart.ShowDialog();
}
}
(Description about ChartForm's at the end of post)
Ok. When I have created the ClassA in Program.cs:
class Program
{
static void Main(string[] args)
{
ClassA class = new ClassA();
class.PlotGrid();
Console.WriteLine("it was shown as parallel with windowsform(the ChartForm)");
}
}
In terminal had shown:
it was shown as parallel with windowsform(the ChartForm) but a ChartForm not shown. I want to create a descructor or other way for ClassA. How i can do it if a parent (ClassA) has children (ChartForm) and until it has a children whom are running - don't close app.
I tried to add in destructor ClassA:
~ClassA()
{
Task.WaitAll(Tasks.ToArray());
}
but it didn't help.
Class ChartForm is from other project, which inherit WindowsForms (Form) and has only one object: Chart.
Please look below:
public partial class ChartForm : Form
{
private List<Complex> valuesForPlotting;
int intervalX;
public ChartForm(List<Complex> valuesForPlotting, int intervalX)
{
InitializeComponent();
this.valuesForPlotting = valuesForPlotting;
this.intervalX = intervalX;
}
private void Form1_Load(object sender, EventArgs e)
{
chart1.ChartAreas[0].AxisX.Interval = intervalX;
chart1.ChartAreas[0].AxisX.Minimum = 0;
chart1.ChartAreas[0].AxisX.Maximum = valuesForPlotting.Max(p=> p.Real)+intervalX;
for (int i = 0; i < valuesForPlotting.Count; i++)
{
chart1.Series["ser1"].Points.AddXY
(valuesForPlotting[i].Real, valuesForPlotting[i].Imaginary);
}
chart1.Series["ser1"].ChartType = SeriesChartType.FastLine;
chart1.Series["ser1"].Color = Color.Red;
}
}

How does one kick off a timed sequence of events on the GUI thread in C#?

I've got an app that has to do the following type of things, preferably on the GUI thread since that's where most of the action is taking place and there's no long-running ops:
Wait 1000
FuncA()
Wait 2000
FuncB()
Wait 1000
FuncC()
I realize I could use a timer with a state-machine style OnTick function, but that seems cumbersome:
int _state;
void OnTick(object sender, EventArgs e) {
switch (_state) {
case 0:
FuncA();
_timer.Interval = TimeSpan.FromSeconds(2);
_state = 1;
break;
case 1:
FuncB();
_timer.Interval = TimeSpan.FromSeconds(1);
_state = 2;
break;
case 2:
FuncC();
_timer.IsEnabled = false;
_state = 0;
}
}
Plus I'd like to be able to make it generic enough to do something like
RunSequenceOnGuiThread(new Sequence {
{1000, FuncA}
{2000, FuncB}
{1000, FuncC}};
Is there an idiomatic way to do this kind of thing? Given all the TPL stuff, or Rx, or even the computation expressions in F# I'd assume one exists, but I'm not finding it.

Observable.Concat(
Observer.Timer(1000).Select(_ => Func1()),
Observer.Timer(2000).Select(_ => Func2()),
Observer.Timer(1000).Select(_ => Func3()))
.Repeat()
.Subscribe();
The only thing you have to do to make this work, is make sure that your Func's return a value (even if that value is Unit.Default, i.e. nothing)
Edit: Here's how to make a generic version:
IObservable<Unit> CreateRepeatingTimerSequence(IEnumerable<Tuple<int, Func<Unit>>> actions)
{
return Observable.Concat(
actions.Select(x =>
Observable.Timer(x.Item1).Select(_ => x.Item2())))
.Repeat();
}

Here's a sketch of this in F#:
let f() = printfn "f"
let g() = printfn "g"
let h() = printfn "h"
let ops = [
1000, f
2000, g
1000, h
]
let runOps ops =
async {
for time, op in ops do
do! Async.Sleep(time)
op()
} |> Async.StartImmediate
runOps ops
System.Console.ReadKey() |> ignore
That's in a console app, but you can just call runOps on the GUI thread. See also this blog.
If you're using VS11/NetFx45/C#5, you can do a similar thing with C# async/await and a List of Tuple of Action delegates.

using the async CTP or .NET 4.5 (C# 5) it's REALLY easy using an async method and the await operator. This can be called directly on the UI thread and it will work as expected.
public async void ExecuteStuff()
{
await TaskEx.Delay(1000);
FuncA();
await TaskEx.Delay(2000);
FuncB();
await TaskEx.Delay(1000);
FuncC();
}

Here's a way to combine "yield return" and the reactive framework to give you a "poor man's async". Basically lets you "await" any IObservable. Here I just use it for timers since that's what you were interested in, but it you can have it "await" button clicks (using a Subject<Unit>) etc before moving on to the next thing as well.
public sealed partial class Form1 : Form {
readonly Executor _executor = new Executor();
public Form1() {
InitializeComponent();
_executor.Run(CreateAsyncHandler());
}
IEnumerable<IObservable<Unit>> CreateAsyncHandler() {
while (true) {
var i = 0;
Text = (++i).ToString();
yield return WaitTimer(500);
Text = (++i).ToString();
yield return WaitTimer(500);
Text = (++i).ToString();
yield return WaitTimer(500);
Text = (++i).ToString();
}
}
IObservable<Unit> WaitTimer(double ms) {
return Observable.Timer(TimeSpan.FromMilliseconds(ms), new ControlScheduler(this)).Select(_ => Unit.Default);
}
}
public sealed class Executor {
IEnumerator<IObservable<Unit>> _observables;
IDisposable _subscription = new NullDisposable();
public void Run(IEnumerable<IObservable<Unit>> actions) {
_observables = (actions ?? new IObservable<Unit>[0]).Concat(new[] {Observable.Never<Unit>()}).GetEnumerator();
Continue();
}
void Continue() {
_subscription.Dispose();
_observables.MoveNext();
_subscription = _observables.Current.Subscribe(_ => Continue());
}
public void Stop() {
Run(null);
}
}
sealed class NullDisposable : IDisposable {
public void Dispose() {}
}
It's a slight modification of Daniel Earwicker's AsyncIOPipe idea: http://smellegantcode.wordpress.com/2008/12/05/asynchronous-sockets-with-yield-return-of-lambdas/

Interesting all the different responses. Here's a simple DIY option that doesn't depend on any other libraries, and doesn't hog thread resources unnecessarily.
Basically, for each action in your list, it creates an onTick function that executes that action, then recursively calls DoThings with the remaining actions and delays.
Here, ITimer is just a simple wrapper around DispatcherTimer (but it would work with a SWF Timer as well, or a mock timer for unit testing), and DelayedAction is just a Tuple with int Delay and Action action
public static class TimerEx {
public static void DoThings(this ITimer timer, IEnumerable<DelayedAction> actions) {
timer.DoThings(actions.GetEnumerator());
}
static void DoThings(this ITimer timer, IEnumerator<DelayedAction> actions) {
if (!actions.MoveNext())
return;
var first = actions.Current;
Action onTick = null;
onTick = () => {
timer.IsEnabled = false;
first.Action();
// ReSharper disable AccessToModifiedClosure
timer.Tick -= onTick;
// ReSharper restore AccessToModifiedClosure
onTick = null;
timer.DoThings(actions);
};
timer.Tick += onTick;
timer.Interval = first.Delay;
timer.IsEnabled = true;
}
}
If you don't want to delve into F# or reference Rx or use .Net 4.5 this is a simple viable solution.
Here's an example of how to test it:
[TestClass]
public sealed class TimerExTest {
[TestMethod]
public void Delayed_actions_should_be_scheduled_correctly() {
var timer = new MockTimer();
var i = 0;
var action = new DelayedAction(0, () => ++i);
timer.DoThings(new[] {action, action});
Assert.AreEqual(0, i);
timer.OnTick();
Assert.AreEqual(1, i);
timer.OnTick();
Assert.AreEqual(2, i);
timer.OnTick();
Assert.AreEqual(2, i);
}
}
And here's the other classes to make it compile:
public interface ITimer {
bool IsEnabled { set; }
double Interval { set; }
event Action Tick;
}
public sealed class Timer : ITimer {
readonly DispatcherTimer _timer;
public Timer() {
_timer = new DispatcherTimer();
_timer.Tick += (sender, e) => OnTick();
}
public double Interval {
set { _timer.Interval = TimeSpan.FromMilliseconds(value); }
}
public event Action Tick;
public bool IsEnabled {
set { _timer.IsEnabled = value; }
}
void OnTick() {
var handler = Tick;
if (handler != null) {
handler();
}
}
}
public sealed class MockTimer : ITimer {
public event Action Tick;
public bool IsEnabled { private get; set; }
public double Interval { set { } }
public void OnTick() {
if (IsEnabled) {
var handler = Tick;
if (handler != null) {
handler();
}
}
}
}
public sealed class DelayedAction {
readonly Action _action;
readonly int _delay;
public DelayedAction(int delay, Action action) {
_delay = delay;
_action = action;
}
public Action Action {
get { return _action; }
}
public int Delay {
get { return _delay; }
}
}

If you can use the C# 4.5 to do it, go with Firoso post: it's the best way accomplish that in C#, exactly what Async was built for.
However, if you can't, there might be some ways to do it. I'd do a "simple" manager to do it:
public partial class Form1 : Form
{
private TimedEventsManager _timedEventsManager;
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
_timedEventsManager
= new TimedEventsManager(this,
new TimedEvent(1000, () => textBox1.Text += "First\n"),
new TimedEvent(5000, () => textBox1.Text += "Second\n"),
new TimedEvent(2000, () => textBox1.Text += "Third\n")
);
}
private void button1_Click(object sender, EventArgs e)
{
_timedEventsManager.Start();
}
}
public class TimedEvent
{
public int Interval { get; set; }
public Action Action { get; set; }
public TimedEvent(int interval, Action func)
{
Interval = interval;
Action = func;
}
}
public class TimedEventsManager
{
private readonly Control _control;
private readonly Action _chain;
public TimedEventsManager(Control control, params TimedEvent[] timedEvents)
{
_control = control;
Action current = null;
// Create a method chain, beginning by the last and attaching it
// the previous.
for (var i = timedEvents.Length - 1; i >= 0; i--)
{
var i1 = i;
var next = current;
current = () =>
{
Thread.Sleep(timedEvents[i1].Interval);
// MUST run it on the UI thread!
_control.Invoke(new Action(() => timedEvents[i1].Action()));
if (next != null) next();
};
}
_chain = current;
}
public void Start()
{
new Thread(new ThreadStart(_chain)).Start();
}
}
Beware that this example is Winforms specific (uses Control.Invoke()). You will need a slightly different version for WPF, which uses the thread dispatcher to achieve the same thing. (if my memory doesn't fail me, you also can use Control.Dispatcher.Invoke(), but keep in mind that it is a different control)

Adding cancel ability and exception handling to async code

I have this sample code for async operations (copied from the interwebs)
public class LongRunningTask
{
public LongRunningTask()
{
//do nowt
}
public int FetchInt()
{
Thread.Sleep(2000);
return 5;
}
}
public delegate TOutput SomeMethod<TOutput>();
public class GoodPerformance
{
public void BeginFetchInt()
{
LongRunningTask lr = new LongRunningTask();
SomeMethod<int> method = new SomeMethod<int>(lr.FetchInt);
// method is state object used to transfer result
//of long running operation
method.BeginInvoke(EndFetchInt, method);
}
public void EndFetchInt(IAsyncResult result)
{
SomeMethod<int> method = result.AsyncState as SomeMethod<int>;
Value = method.EndInvoke(result);
}
public int Value { get; set; }
}
Other async approaches I tried required the aysnc page attribute, they also seemed to cancel if other page elements where actioned on (a button clicked), this approach just seemed to work.
I’d like to add a cancel ability and exception handling for the longRunningTask class, but don’t erm, really know how.

In example:
public class ValueEventArgs : EventArgs
{
public int Value { get;set;}
}
public class ExceptionEventArgs : EventArgs
{
public Exception Exception { get;set;}
}
public class LongRunningTask
{
private bool canceled = false;
public event EventHandler<ValueEventArgs> Completed = delegate {}
public event EventHandler<ExceptionEventArgs> GotError = delegate {}
public void Cancel()
{
canceled = true;
}
public void FetchInt()
{
try
{
int result = 0;
for (int i = 0; i < 1000; i++)
{
if (canceled)
return;
result++;
}
Completed(this, new ValueEventArgs {Value = result});
}
catch(Exception exc)
{
GotError(this, new ExceptionEventArgs { Exception = exc });
}
}
public void BeginFetchInt()
{
ThreadPool.QueueUserWorkItem(i => FetchInt());
}
}
And somewhere:
LongRunningTask task = new LongRunningTask();
task.Completed +=new EventHandler<ValueEventArgs>(task_Completed);
task.GotError +=new EventHandler<ExceptionEventArgs>(task_GorError);
task.BeginFetchInt();
//in any moment until it calculates you may call:
task.Cancel();

Develop Reference

C# (C-Sharp) is a programming language developed by Microsoft that runs on the .NET Framework.

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