UI freezing while executing async command (AvaloniaUI + ReactiveUI)

Question

I am trying to create a MVVM Avalonia app using the ReactiveUi and want to execute a command async in order to keep the user interface working. However this is not the case. After hitting my button, the ui freezes until the command has finished executing even though i am running it async.

Does somebody know, what i am doing wrong here?

This is what i am currently doing:

ViewModel:

public LoginViewModel()
{
    TryConnectAsyncCommand = ReactiveCommand.CreateFromTask(TryConnectAndLogin);
}

public ReactiveCommand<Unit, Unit> TryConnectAsyncCommand { get; }

async Task TryConnectAndLogin()
{
    ErrorFlag = false;
    ClientConversationManager.TryConnect(EnteredInstance, EnteredPort);
    if (ClientConversationManager.IsConnected)
    {
            
    }
    else
    {
        ErrorFlagContent = "Could not connect to server :/";
        ErrorFlag = true;
    }
}

View:

Command="{Binding TryConnectAsyncCommand}"

There are no awaits in your function. Perhaps there should be something like await ClientConversationManager.TryConnectAsync( or similar — Charlieface
– Charlieface, Commented Jun 4, 2023 at 11:04
Making the other functions async and awaiting them sadly does not solve my problem. Also why can't i just await the entire TryConnectAndLogin? — timkicker
– timkicker, Commented Jun 4, 2023 at 11:06
No it will block the thread unless you have an await. Marking it async doesn't magically do anything until you have an await — Charlieface
– Charlieface, Commented Jun 4, 2023 at 11:08
So i awaited the other functions but it sadly did not solve my problem — timkicker
– timkicker, Commented Jun 4, 2023 at 11:15

Lukasz Szczygielek · Accepted Answer · 2023-06-12 17:49:43Z

1

Your method TryConnectAndLogin is synchronized. You can make it async using Task.Run (standard way) or Observable.Start (rx way).

public LoginViewModel()
{
    TryConnectAsyncCommand = ReactiveCommand.CreateFromObservable(TryConnectAndLogin);
}

public ReactiveCommand<Unit, Unit> TryConnectAsyncCommand { get; }

private IObservable<Unit> TryConnectAndLogin()
{
    return Observable.Start(() =>
    {
        ErrorFlag = false;
        ClientConversationManager.TryConnect(EnteredInstance, EnteredPort);
        if (ClientConversationManager.IsConnected)
        {
                
        }
        else
        {
            ErrorFlagContent = "Could not connect to server :/";
            ErrorFlag = true;
        }
    });
}

answered Jun 12, 2023 at 17:49

Lukasz Szczygielek

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