C# pause foreach loop until button pressed

Question

Using C#, I have list of methods (Actions). I then have a method to invoke action using a foreach loop. A button click calls the method which in turn invokes every action in the list in one go. What I am after is for the click to only execute one action per click. Thanks in advance.

private static List<Action> listOfMethods= new List<Action>();

listOfMethods.Add(() => method1());
listOfMethods.Add(() => method2());
listOfMethods.Add(() => method3());
//====================================================================
private void invokeActions()
{
   foreach (Action step in listOfMethods)
   {
       step.Invoke();
       //I want a break here, only to continue the next time the button is clicked
   }
}
//====================================================================
private void buttonTest_Click(object sender, EventArgs e)
    {
        invokeActions();
    }

Why do you choose to use a `List`? How many times do you plan on iterating the structure? Is it just once until all the methods are called or do you plan on looping through? Depending on your intention, a `Stack` or `Queue` could be a better choice. — Ian R. O'Brien, Sep 03 '15 at 19:15
Honestly, because I'm new to programming and was not aware of these :) — justlearning, Sep 03 '15 at 19:49

score 3 · Accepted Answer · answered Sep 03 '15 at 19:12

You can add a step counter :

private static List<Action> listOfMethods= new List<Action>();
private static int stepCounter = 0;

listOfMethods.Add(() => method1());
listOfMethods.Add(() => method2());
listOfMethods.Add(() => method3());
//====================================================================
private void invokeActions()
{
       listOfMethods[stepCounter]();

       stepCounter += 1;
       if (stepCounter >= listOfMethods.Count) stepCounter = 0;
}
//====================================================================
private void buttonTest_Click(object sender, EventArgs e)
    {
        invokeActions();
    }

Thank you and everyone else. I used this solution in the end. — justlearning, Sep 03 '15 at 19:46

score 1 · Answer 2 · answered Sep 03 '15 at 19:13

You need to persist some state in between button clicks, so that you know where you left off from the last time. I suggest using a simple counter:

private int _nextActionIndex = 0;

private void buttonTest_Click(object sender, EventArgs e)
{
    listOfMethods[_nextActionIndex]();
    if (++_nextActionIndex == listOfMethods.Count)
        _nextActionIndex = 0;    // When we get to the end, loop around
}

This executes the first action, then the next, etc. each time the button is pressed.

score 1 · Answer 3 · answered Sep 03 '15 at 19:18

First write a method to generate a Task when a particular Button is next pressed:

public static Task WhenClicked(this Button button)
{
    var tcs = new TaskCompletionSource<bool>();
    EventHandler handler = null;
    handler = (s, e) =>
    {
        tcs.TrySetResult(true);
        button.Click -= handler;
    };
    button.Click += handler;
    return tcs.Task;
}

Then just await it in your method when you want it to continue after the next button press:

private async Task invokeActions()
{
    foreach (Action step in listOfMethods)
    {
        step.Invoke();
        await test.WhenClicked();
    }
}

score 0 · Answer 4 · answered Sep 03 '15 at 19:23

If you only need to execute the methods once, I would suggest adding them to a Queue<T> so state does not need to be maintained.

private static Queue<Action> listOfMethods = new Queue<Action>();
listOfMethods.Enqueue(method1);
listOfMethods.Enqueue(method2);
listOfMethods.Enqueue(method3);   

private void buttonTest_Click(object sender, EventArgs e) {
    if (listOfMethods.Count > 0) {
        listOfMethods.Dequeue().Invoke();
    }
}

C# pause foreach loop until button pressed

4 Answers4