Stored values send to Console in different time intervals

Question

I've figured out how to store Data from a .csv to a List<>.

I've two Lists: ListA which contains the timestamp for each value and ListB which contains the values.

It looks like this:

A (time [ms])  | B (value)
---------------------------
0,00           | 49,33
154,71         | 49,46
244,92         | 49,72
855,11         | 49,64

...
And so on (over 50.000 values)

My actual issue is: I want to send the values to the console using WriteLine(listA[i]); at the (nearly) exact time like the timestamp of the actual value.

I thought about a stopwatch which i compare with the timestamps to give the right value out at the right moment?

Is this possible?

---

Update #1:

Here is my code. It works (kind of). But i'm not sure if there is a much better solution?

stopwatch.Start();

while(true)
{ 
    for (int i = 0; i < 50000; i++)
    {
        if (Math.Abs(stopwatch.Elapsed.TotalMilliseconds - Convert.ToDouble(listA[i]) * 1000) < 10)
        {
            Console.WriteLine(listB[i]);
        }
    }
    Thread.Sleep(5);
}

Update #2:

I'm trying to understand the solution of Mong Zhu @disclaimer. My target is to create a method which get initiated by a timer (every 100ms as example). I already have the code around this Problem is: Timestamp and Stopwatch are sometimes not synced and it skips some values.

Here is my method (called every 100ms):

public double getvalue()
    {

        if (stopwatch.ElapsedMilliseconds > Convert.ToDouble(ListA[ListA.Count-1])*1000)
        {
            stopwatch.Stop();
        }
        else
        {
            for (var i = 0; i < ListA.Count; i++)
            {
                if (Math.Abs(stopwatch.ElapsedMilliseconds - Convert.ToDouble(ListA[i]) * 1000) < 5)
                {
                    value = Convert.ToDouble(ListB[i]);
                    break;
                }
            }
        }

        return value;
    }

Answer 1

Your implementation would be much easier if instead of having two separate lists you have only one list of the type you need. Let me explain:

You create a class with the properties you need:

public class YourClass
{
     public long TimeMS {get; set;}
     public Double Value {get; set;}
}

Then you can simply create a List<YourClass>

List<YourClass> list = new List<YourClass>();

list.Add( new YourClass { TimeMS = 154.71, Value = 49.46 } );

Then it would be much easier to iterate:

foreach(YourClass c in list)
{
     //DO ALL YOUR WORK
     Console.WriteLine(c.TimeMS.ToString() + ": " + c.Value.ToString());
}

Answer 2

If you want to use a StopWatch then I would switch the for and the while loop. Only iterate to the next position after you have overstepped the time interval and wrote the value to the console. Here is an examplary program:

void Main()
{
    Stopwatch stopWatch = new Stopwatch();
    List<int> ListA = new List<int>() { 0, 154, 244, 855 };
    List<double> ListB = new List<double>() { 49.33, 49.46, 49.72, 49.64 };

    stopWatch.Start();

    for (int i = 0; i < ListA.Count; i++)
    {
        while (stopWatch.ElapsedMilliseconds < ListA[i] * 1000) 
        {
            Thread.Sleep(5); 
         }

        Console.WriteLine($"Value: {ListB[i]} TIME: {stopWatch.ElapsedMilliseconds}");
    }

    stopWatch.Stop();

    Console.ReadKey();
}

Problems in your code:

1) for (int i = 0; i < 50000; i++)
Preferably dont' use a fixed number for the for loop if you iterate over a collection. The collection might change in size and the fixed number will lead either to an out of bounds exception or to not handled values. Use Count if it is a List or Length if it is an array

2) In each while-iteration you are iterating over the entire array. This is a strong overhead, if you actually want to print value by value.

Disclaimer. The while loop in my solution is called buisy-waiting. This is not really adviseable since the CPU is occupied while doing actually nothing. A preferable solution would be to use a timer:

System.Timers.Timer timer = new System.Timers.Timer();
// register the event which will be fired
timer.Elapsed += PrintValuesAtTime;
timer.Interval = 1; // an intervall of 0 is not allowed
timer.AutoReset = true; // repeated execution of the timer
timer.Start(); // start the timer

Console.ReadLine();

I would make a new list which contains all timestamp differences from ListA which can be used as an intervall for the next printing. Something like:

List<int> ListAIntervals = new List<int>() { 0, 154-0, 244-154, 855-244 };

and in the Elapsed event handler you can handle the printing logic. You would need an external counter to iterate over you collection:

private void PrintValuesAtTime(object sender, EventArgs args)
{
    System.Timers.Timer timer = sender as System.Timers.Timer;
    // only print values if there are enough values
    if (counter < ListAIntervals.Count && counter < ListB.Count)
    {
        Console.WriteLine($"Value: {ListB[counter]}");
        // there needs to be enough intervals left to go one more time
        if (counter < ListAIntervals.Count - 1 && counter < ListB.Count - 1) 
        {
            counter++;
            timer.Interval = ListAIntervals[counter] * 1000; // to make it in msec
        }
        else
        {
            // stop the timer
            timer.AutoReset = false;
        }
    }       
}