Can Execute Select Case methodname Case "Address" Return Try Cast(method, Model View. Execute Select Case methodname Case "Address" Try Cast(method, Model View. Delete Command("Address", Me) Property Selected Address As Model.
Can Delete Numbers Case Else : Return False End Select End Function Public Event Can Execute Changed(sender As Object, e As Event Args) Implements ICommand. Delete Numbers() Case Else End Select End Sub End Class Public Class Contact MV Property Contact As Model. Contact Mod Property Add Address Command As New Commands.
ID, False)) End If End Sub Public Sub Delete Address() If Is Nothing(Selected Address) = False Then Try Contact. Remove(Selected Address) Catch ex As Exception Msg Box("Address not found") End Try End If End Sub Public Function Can Delete Address() If Is Nothing(Selected Address) Then Return False Else Return Contact. Contains(Selected Address) End If End Function End Class The problem is that the Canexecutechanged is firing only at start, I actually want to get the delete button enabled only when something in the listbox is selected, and I want to get it done by MVVM - ICommand binding method. Can Execute Changed Add Handler(By Val value As Event Handler) If _Can Execute Is Not Nothing Then Add Handler Command Manager. Invoke() End Sub #End Region End Class After thorough googling or MSDN searching on relay command the core difference between it and ICOMMAND found that raise event is forced to requery canexecute status, and the code to force is "Command Manager. because although this works functionally, and is ok for small applications, it is indiscriminate and will potentially re-query every command!
I have now made changes to my code and can work much more better and good at MVVM path.
You can call Raise Can Execute Changed in the For example Property Changed Eventhandler. When using the Relay Command class, a command class used for MVVM development, you may find times when a button that is enabled or disabled based on Relay Command.Can Execute does not refresh until a keyboard or mouse click.This code works mostly correct but i can not make method Can Save Item to work properly.I don't know how to tell to Save Command that properties of View Model was changed.