First of all, I understand that the ref, in and out parameters are forbidden in asynchronous tasks.
However, as I have this need, I’m trying to find the cleanest, simplest and most effective solution.
And unintentionally I’ve created a case that seems to work (I realised later). But I need your help to better understand why this case works as opposed to a simple string.
I’m in C# / WPF and I’m trying to apply the MVVM pattern.

This is what is called from the ViewModel

await _NetworkUtil.ExecuteNetworkTask(NetworkStep1,NetworkStep2, DomainFQDN, 1000, 4, Gateway, IPAddress, SubNetMask, DNSSrvIPAddress, DomainController);

This is the method called from a utility class

public async Task ExecuteNetworkTask(Result networkStep1, Result networkStep2, string domaineFqdn, int timeout, int nbPing,string gateway, string ipAddress, string subnetMask, string dnsSrvIPAddress, string domainController)

I need to update the parameters NetworkStep1, NetworkStep2, DomainController
Now for some important details. “Result” networkStep1 / networkStep2 is a custom class

    public class Result
{
    private bool _success;
    public bool Success {
        get { return _success; } 
        set { _success = value; } }

    private StringBuilder _message;
    public StringBuilder Message
    {
        get { return _message; }
        set
        {
            _message = value;
           
        }
    }

    private StringBuilder _exception;
    public StringBuilder Exception
    {
        get { return _exception; }
        set
        {
            _exception = value;

        }
    }

    public Result()
    {
        _message = new StringBuilder();
        Exception = new StringBuilder();
    }

    public void UpdateLog(string message)
    {
        Message.AppendLine(message);
        OnLogUpdated(message);
    }

    public void UpdateEx(string message)
    {
        Exception.AppendLine(message);
        OnLogUpdated(message);
    }

    public event Action<string> LogUpdated;
    protected virtual void OnLogUpdated(string updatedLog)
    {
        LogUpdated?.Invoke(updatedLog);
    }
}

This is how the Result is initialised before the task is called (in ViewModel)

NetworkStep1 = new Result();
NetworkStep1.LogUpdated += UpdateTextBoxLog;
NetworkStep2 = new Result();
NetworkStep2.LogUpdated += UpdateTextBoxLog;

await _NetworkUtil.ExecuteNetworkTask(NetworkStep1,NetworkStep2, DomainFQDN, 1000, 4, Gateway, IPAddress, SubNetMask, DNSSrvIPAddress, DomainController);

The .LogUpdated += UpdateTextBoxLog is used to update a log window in real time when a Result is updated.
Example within the ExecuteNetworkTask :

networkStep1.UpdateLog(‘Connected to network’)

These are the declarations in ViewModel for NetworkStep1/2. “Session” is an instantiation of the M_Session Model.

    public Result NetworkStep1
    {
        get { return Session.NetworkEtape1; }
        set
        {
            Session.NetworkEtape1 = value;
            OnPropertyChanged(nameof(NetworkStep1));
        }
    }

public string DomainController
{
    get { return Session.DomainController; }
    set
    {
        Session.DomainController = value;
        OnPropertyChanged(nameof(DomainController));
    }
}

That’s it for the summary, in the hope that it’s not too confusing and at the same time sufficiently complete.
To summarise now, I need to update the ViewModel’s DomainControler property via the ExecuteNetworkTask async task. I could, of course, set it as a return, but as I could potentially have several properties to update, I thought it would be more practical to set them as parameters. As the DomainController update didn’t work, I finally realised that I couldn’t use a REF in an async task.
BUT … surprisingly the result class networkStep1 and 2 update very well! Since the log is updated in real time and the control to move on works well.

if(NetworkStep1.Success && NetworkStep2.Success)
{
    CurrentStepView = new UserAuthentification();
}

Basically, I didn’t create the Result class for this purpose at all, but the way I’m using it, it seems (unless it’s a big illusion) that the way I’m using it allows it to be updated within an async task.
Could you help me understand how? So that I can update the DomainController.
Thank you all for your help