How can I start async tasks from a list of tasks? or How to count tasks?

Question

I have a few objectives, which lead to this combination of code:

1. Call some API functions async, so they run parallel and don't freeze the UI
2. Show a progressBar in the meantime as the comboBoxes get filled with the API-data

I would like to keep my tasks in a List or other data structure in order to count them and assign this count value to the Maximum property in my progressBar.

public async void retrieveAPIData()
{
    // hide everything except the progressbar
    var controls = this.Controls.Cast<Control>().Where(
        control => !control.Equals(progressBar));
    foreach (var control in controls)
    {
        control.Visible = false;
    }

    // handler for when the progress gets Report-ed (Report function)
    var progress = new Progress<int>(percent =>
    {
        progressBar.Value += percent;
    });

    // api singleton
    var proErp = ProERP.Instance;

    // attempt at a List that combines tasks to their comboBox through a data class
    List<ControlFiller> tasks = new List<ControlFiller>()
    {
        new ControlFiller()
        {
            task = proErp.GetColumns(progress),
            ComboBox = squareHollowSection
        },
        new ControlFiller()
        {
            task = proErp.GetProfiles(progress),
            ComboBox = typeOfProfile
        },
    };

    // most important reason to store the tasks in a List, to count them to know how
    // many steps there will be
    progressBar.Maximum = tasks.Count;

    //var columnsTask = proErp.GetColumns(progress);
    //var profilesTask = proErp.GetProfiles(progress);

    //this.squareHollowSection.DataSource = await columnsTask;
    //this.typeOfProfile.DataSource = await profilesTask;

    // The design time errors occur here!
        foreach (var task in tasks)
        {
            task.ComboBox.DataSource = await task.task;
        }

    // To not hide the progressBar too fast for development
    Thread.Sleep(2000);
    // tasks finished
    progressBar.Visible = false;
    // show the other Controls again
    foreach (var control in controls)
    {
        control.Visible = true;
    }
}

In the task I call (example from Profile):

public async Task<List<Profile>> GetProfiles(IProgress<int> progress)
{
    var request = new RestRequest("Profile", Method.GET);
    IRestResponse response = await client.ExecuteAsync(request);
    progress.Report(1);
    return new JsonDeserializer().Deserialize<List<Profile>>(response);
}

ControlFiller class:

internal class ControlFiller
{
    public Task task;
    public ComboBox ComboBox;
}

However this does not work as I use Task in ControlFiller which returns void, I however can neither return as specific class as it would only work for 1 task or Object as the Task Generic of Task<Object> cannot be converted implicitly. Is there a way to create a list of tasks to count, let them run and assign their awaited value to a DataSource for my form?

The linked answer is not even helpful as I want to assign the returned values dynamically, now I need to know which value sits in which index.

edit:

Even with a common foreach loop I cannot await the values as my DataStructure will cast(?) Task<Column> and Task<Profile> to a Task that doesn't return anything (void). Is there a way to

1. Count the Tasks (not necessarily in a Data Structure).
2. If they are added to a Data Structure, await their values and assign it to their respective ComboBox.

---

Self answer (which I cannot post because the question is closed) I moved the assigning of the ComboBox values to the Task itsels, than I don't need the return value.

  public async void retrieveAPIData()
        {
            var controls = this.Controls.Cast<Control>().Where(control => !control.Equals(progressBar));

            foreach (var control in controls)
            {
                control.Visible = false;
            }

            var progress = new Progress<int>(percent =>
            {
                progressBar.Value += percent;
            });
            var proErp = ProERP.Instance;

            var GetColumnsTask = proErp.GetColumns(progress, squareHollowSection);
            var GetProfileTask = proErp.GetProfiles(progress, typeOfProfile);

            ArrayList list = new ArrayList()
            {
                GetColumnsTask, GetProfileTask
            };

            await GetColumnsTask;
            await GetProfileTask;

            progressBar.Maximum = list.Count;

            Thread.Sleep(2000);
            progressBar.Visible = false;
            foreach (var control in controls)
            {
                control.Visible = true;
            }
        }

Task

 public async Task<List<Profile>> GetProfiles(IProgress<int> progress, ComboBox comboBox = null)
        {
            var request = new RestRequest("Profile", Method.GET);
            IRestResponse response = await client.ExecuteAsync(request);
            progress.Report(1);
            var data = new JsonDeserializer().Deserialize<List<Profile>>(response);
            comboBox.DataSource = data;
            return data;
        }