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mvvmmauieventtocommand

MAUI EventToCommandBehavior

XAML:

<ContentPage.Behaviors>
    <toolkit:EventToCommandBehavior
        EventName="OnAppearing"
        Command="{Binding AppearingExeCommand}" />
</ContentPage.Behaviors>

ViewModel:

[RelayCommand]
public void AppearingExe()
{
    try
    {
        WeakReferenceMessenger.Default.Reset();
        if (!WeakReferenceMessenger.Default.IsRegistered<MyMessage>(this))
        {
            WeakReferenceMessenger.Default.Register<MyMessage>(this, OnMessageReceived);
        }
    }
    catch(Exception er)
    {
        Shell.Current.DisplayAlert("Error!", er.Message, "OK");
    }
}

Running an error:Exception has been thrown by the target of an invocation

What is the reason? How should I handle it

Solution

  • There is no OnAppearing event on ContentPage, only a method with that name. You need to use the Appearing event of ContentPage:

    <ContentPage.Behaviors>
    <toolkit:EventToCommandBehavior
        EventName="Appearing"
        Command="{Binding AppearingExeCommand}" />
</ContentPage.Behaviors>