Using Command CanExecute

[pedroivobraga]

Hi,
I'm trying to use the AsyncCommand with CanExecute, but I'm not sure how to revalidate the CanExecute.
I'm calling RaiseCanExecuteChanged, but it is not working.

Anyone could help me?

I'm using Xamarin.Forms v5.0

[robertodalmonte]

Hi Pedro,
I run into the same issue myself...I guess the problem is that the IAsyncCommand interface (in the NuGet package) is missing the RaiseCanExecuteChanged() method, while the mvvm-helpers repository has it.
So in order to update the CanExecute method every time a property changes, you have to declare the command using the class, not the interface. The class has the method, the interface does not.

internal class CheckViewModel : ViewModelBase
{
private AsyncCommand CheckCommand { get; }
//private IAsyncCommand CheckCommand {get;}//doesn't work
public CheckViewModel()
{
CheckCommand = new AsyncCommand(CheckOfficeExists, CanCheckOfficeExists);
this.PropertyChanged += (_, _) => CheckCommand.RaiseCanExecuteChanged();
}

    private bool CanCheckOfficeExists(object args)
    {
        return IsValid;
    }

    private async Task CheckOfficeExists()
    {
          DoSomething();
    }

[robertodalmonte]

oops...the command must be public
public AsyncCommand CheckCommand { get; }