public App()
{
InitializeComponent();
MainPage = new MainPage();
_mainVm = (MainVm)MainPage.BindingContext;
}
private void OnBindingContextChanged(object sender, EventArgs e)
{
if (_bindingContext != null)
{
_bindingContext.Alert -= Alert;
}
_bindingContext = BindingContext as MainVm;
if (_bindingContext != null)
{
_bindingContext.Alert += Alert;
}
}