Question

At the moment I have the following Command class:

Public Class SubscribeCommand
    Implements ICommand

    Private ReadOnly _vm As MainWindowViewModel

    Public Sub New(ByVal vm As MainWindowViewModel)
        _vm = vm
    End Sub

    Public Function CanExecute(ByVal parameter As Object) As Boolean Implements System.Windows.Input.ICommand.CanExecute
        Return Not String.IsNullOrEmpty(_vm.Symbol)
    End Function

    Public Event CanExecuteChanged(ByVal sender As Object, ByVal e As System.EventArgs) Implements System.Windows.Input.ICommand.CanExecuteChanged

    Public Sub Execute(ByVal parameter As Object) Implements System.Windows.Input.ICommand.Execute
        _vm.Subscribe()
    End Sub
End Class

In a tutorial i read, you have to implement add {} and remove {} for the canExecuteChanged-Event. But how can i do that, with vb.net?

thanks a lot..

Answer 1

I don’t think you’re required to implement the add and remove pieces for the CanExecuteChanged event. I’m pretty sure it’ll work just fine the way you have it now. But if you did want to for some reason (to make it match what you see in this post in C#, for instance), you would change

Public Event CanExecuteChanged(ByVal sender As Object, ByVal e As System.EventArgs)

to

Public Custom Event CanExecuteChanged As EventHandler

    AddHandler(ByVal value As EventHandler)

        CommandManager.RequestSuggested += value

    End AddHandler

    RemoveHandler(ByVal value As EventHandler)

           CommandManager.RequestSuggested -= value

    End RemoveHandler

End Event