How to pause a loop without blocking the UI and restart with button

Question

I am looking for the best practice to pause foreach or for loops (it has to wait until the user inserts text and presses a button to confirm).

private void btnStarten_Click(object sender, RoutedEventArgs e)
{            
      //using a foreach loop blocks the UI I read? 

      for (int i = list.Count; i >= 0; i--)
      {
          //Here I want to pauze the loop and being able to insert a valeu in a textbox after I 
          //clicked another button to confirm, I resume the Loop
      }   
}

for and foreach both block the UI in the code you've provided. You should probably separate your code. Store i somewhere else to keep track of where you are, and then have the button clicks trigger iteration. — ProgrammingLlama
– ProgrammingLlama, Commented Apr 17, 2020 at 8:45

Maxim Lejaeghere · Accepted Answer · 2020-04-17 17:28:44Z

1

My final code looked like this:

private void btnResultaat_Click(object sender, RoutedEventArgs e)
        {
            if (leerlingIngave.RandomLijst.Count - 1 == leerlingIngave.AntwoordEnUitkomstLijst.Count)
//I compair my 2 lists to eachother (theRandom list was already filled)
            {

                btnResultaat.IsEnabled = false; // I ended the loop by disabeling the button
                leerlingIngave.VerderZettenLoop();
            }
            else
            {
                leerlingIngave.VerderZettenLoop();
            }
        }

public void VerderZettenLoop() // Add object to the list
        {

                    AntwoordEnUitkomstLijst.Add(new LeerlingModel(Uitkomst, Antwoord));
        }

answered Apr 17, 2020 at 17:28

Maxim Lejaeghere

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Comments

ProgrammingLlama · Accepted Answer · 2020-04-17 08:57:16Z

I would recommend separating out your code a bit, rather than having a loop that "waits".

For example:

private int _loopIndexer = 0;

public void ContinueLoop()
{
    for (; _loopIndexer < list.Count; ++_loopIndexer)
    {
        if (list[_loopIndexer].Property == "value")
        {
            // on a matching condition do something and then exit the method
            ++_loopIndexer; // we need to increment the position before we exit the method
            return;
        }
    }
}

private void btnStarten_Click(object sender, RoutedEventArgs e)
{
    // reset to the beginning
    _loopIndexer = 0;
    ContinueLoop();
}

private void btnContinue_Click(object sender, RoutedEventArgs e)
{
    // If the end of the loop is reached, quit (or do whatever)
    if (_loopIndexer + 1 == list.Count)
    {
        // _loopIndexer = 0; // you could reset it to 0 if you wanted to loop again
        return;
    }

    ContinueLoop();
}

The idea is that btnStarten will start the loop, and the loop will stop whenever a condition is met. Then, when you click the Continue button, it will continue the loop if there are any list items left.

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