Repository navigation
ViewModel with async Command #4965
Description
Alex Prinias asked 2026-04-19 10:24:50 UTC
Hi guys,
If I have a ViewModel with an async method, how can I define a Command to bind to a button in my View?
The problem I see is that when I click the Login button, I am not navigated from my login View to my main view, but if I click somewhere on the page, then the navigation happens indeed. If I remove async from the method, this works from the first click.
I am reading in the docs about Application.Update(this), but I don't think it is reasonable to call Application.Update(this) from the ViewModel, what "this" should be in that case?
Is this even possible, or am I trying in vain?
Best regards,
Alex
For example, I have a LoginViewModel with the following method.
private async Task LoginAsync()
{
try
{
IsBusy = true;
ErrorMessage = string.Empty;
var success = await _authService.LoginAsync(Username, Password);
if (!success)
ErrorMessage = "Invalid username or password.";
// If success, AuthenticationService will raise event and ApplicationViewModel will handle shell swap
}
catch (Exception ex)
{
ErrorMessage = $"Login failed: {ex.Message}";
}
finally
{
IsBusy = false;
}
}
And I am trying to define my command in the constructor:
public LoginViewModel(IAuthenticationService authService)
{
_authService = authService;
LoginCommand = new Command(
execute: async () => { await LoginAsync(); },
canExecute: () => !IsBusy && !string.IsNullOrWhiteSpace(Username) && !string.IsNullOrWhiteSpace(Password));
}
and in my LoginView:
btnLogin.Command = _vm.LoginCommand;
Activity
itg-assistant commentedon Jun 17, 2026
Julie (ITG) answered 2026-04-21 14:48:59 UTC
works when
is a Wisej control. But in your case,
is the ViewModel. So don't use
Instead, you can save the context before the await by doing:
Then when you need to update the UI you can do:
More information on Application.Current: https://docs.wisej.com/api/wisej.web/general/application#current
itg-assistant commentedon Jun 17, 2026
Alex Prinias answered 2026-04-21 18:38:25 UTC
Dear Julie,
thanks for your answer.
So you mean in the definition of the LoginCommand in the ViewModel's constructor:
LoginCommand = new Command(
execute: async () => { var context = Application.Current; await LoginAsync(); Application.Update(context); },...
However I find it a bit strange, in the sense I would expect my ViewModel to be unaware of Wisej's Application.Current etc. What if I wanted to use the same ViewModel for a WinForms application and not a Wisej one?
Best regards,
Alex
itg-assistant commentedon Jun 17, 2026
Julie (ITG) answered 2026-04-23 14:19:41 UTC
You're correct that the call to Application.Update does not have to happen in the ViewModel.
Here's a sample showing how to do async commands in Wisej MVVM.
The async method should be in the ViewModel,
Navigation or shell swapping should happen in an application-level ViewModel reacting to authentication state
Any Wisej-specific Application.Update(...) usage should be hidden in infrastructure that restores/pushes the Wisej context rather than called from the ViewModel itself.
In the sample, look at:
LoginViewModel.cs for the async login logic
ApplicationViewModel.cs for shell swapping (MainViewModel and LoginViewModel are the shells)
WisejAsyncCommand.cs and WisejUiDispatcher.cs for the Wisej-aware command/context handling
WisejUIDispatcher for the call to Application.Update
Window1.cs for the shell host.