Following code snippet contains the implementation of ICommand interface. The code below shows a generic implementation of ICommand interface.
Code:
Namespace Commands
Public Class DelegateCommand(Of T)
Implements ICommand
Private executeMethod As Action(Of T)
Private canExecuteMethod As Func(Of T, Boolean)
'''
''' Occurs when changes occur that affect whether or not the command should execute.
'''
'''
''' Initializes a new instance of class.
'''
''' Method that execute when command is invoked.
Public Sub New(ByVal executeMethod As Action(Of T))
MyClass.New(executeMethod, Nothing)
End Sub
'''
''' Initializes a new instance of class.
'''
''' Method that execute when command is invoked.
''' Method that determines whether the command can execute in its current state.
Public Sub New(ByVal executeMethod As Action(Of T), ByVal canExecuteMethod As Func(Of T, Boolean))
If executeMethod Is Nothing AndAlso canExecuteMethod Is Nothing Then
Throw New ArgumentNullException("executeMethod")
End If
Me.executeMethod = executeMethod
Me.canExecuteMethod = canExecuteMethod
End Sub
'''
''' Determines whether the command can execute in its current state.
'''
''' Data used by the command. If the command does not require data to be passed, this object can be set to null.
''' True if this command can be executed; otherwise, False.
Public Function CanExecute(ByVal parameter As Object) As Boolean Implements System.Windows.Input.ICommand.CanExecute
If canExecuteMethod Is Nothing Then
Return True
End If
If parameter Is Nothing Then
Return canExecuteMethod(Nothing)
End If
Return canExecuteMethod(CType(parameter, T))
End Function
'''
''' Called when the command is invoked.
'''
''' Data used by the command. If the command does not require data to be passed, this object can be set to null.
Public Sub Execute(ByVal parameter As Object) Implements System.Windows.Input.ICommand.Execute
If executeMethod Is Nothing Then
Return
End If
If parameter Is Nothing Then
executeMethod(Nothing)
Else
executeMethod(CType(parameter, T))
End If
End Sub
'''
''' Raises the CanExecuteChanged event.
'''
Public Sub RaiseCanExecuteChanged()
RaiseEvent CanExecuteChanged()
End Sub
End Class
End Namespace
1 comments :
Thanks for this post
I have used this code in my project
but thing to complete this for canExecuteMethod
please add this code for canExecuteMethod to
Public Sub RaiseCanExecuteChanged()
RaiseEvent CanExecuteChanged(Me, EventArgs.Empty)
End Sub
when you need that UI may eanble the call commandObject.RaiseCanExecuteChange from you viewModel
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