WPF AttachedCommandsBehavior in VB.NET - wpf

Question

Can anybody give me an example how to implement AttachedCommands?
There are some examples in C# and I think it is very similar to C# but I have problems to translate the code to VB.NET.
At the moment my try to translate a C# AttachedCommand-Class to VB.net looks like that:
Imports System
Imports System.Collections.Generic
Imports System.Linq
Imports System.Text
Imports System.Windows
Imports System.Windows.Input
Imports System.Reflection
Public Class AttachedCommand
Inherits DependencyObject
#Region "CommandParameter-Class"
Private NotInheritable Class CommandParameter
Public Shared ReadOnly Property DefaultCP() As CommandParameter
Get
Return New CommandParameter()
End Get
End Property
Private _command As ICommand
Public Property Command() As ICommand
Get
Return _command
End Get
Set(ByVal value As ICommand)
_command = value
End Set
End Property
Private _eventName As String
Public Property EventName() As String
Get
Return _eventName
End Get
Set(ByVal value As String)
_eventName = value
End Set
End Property
Private _callBack As [Delegate]
Public Property Callback() As [Delegate]
Get
Return _callBack
End Get
Set(ByVal value As [Delegate])
_callBack = value
End Set
End Property
End Class
#End Region
#Region "Properties"
Private Shared _parameter As IDictionary(Of DependencyObject, CommandParameter)
Private Shared Property Parameter() As IDictionary(Of DependencyObject, CommandParameter)
Get
Return _parameter
End Get
Set(ByVal value As IDictionary(Of DependencyObject, CommandParameter))
_parameter = value
End Set
End Property
Public Property Command() As ICommand
Get
Return GetValue(CommandProperty)
End Get
Set(ByVal value As ICommand)
SetValue(CommandProperty, value)
End Set
End Property
Public Shared ReadOnly CommandProperty As DependencyProperty = _
DependencyProperty.Register("Command", _
GetType(ICommand), GetType(AttachedCommand), _
New UIPropertyMetadata(AddressOf CommandChanged))
Public Property EventName() As String
Get
Return GetValue(EventNameProperty)
End Get
Set(ByVal value As String)
SetValue(EventNameProperty, value)
End Set
End Property
Public Shared ReadOnly EventNameProperty As DependencyProperty = _
DependencyProperty.Register("EventName", _
GetType(String), GetType(AttachedCommand), _
New UIPropertyMetadata(AddressOf EventNameChanged))
#End Region
#Region "Event-Handler"
Public Shared Sub CommandChanged(ByVal dependencyObject As DependencyObject, ByVal args As DependencyPropertyChangedEventArgs)
If Not Parameter.ContainsKey(dependencyObject) Then
Parameter.Add(dependencyObject, CommandParameter.DefaultCP)
End If
If (Not Parameter(dependencyObject).Callback = Nothing) AndAlso (Not args.OldValue = Nothing) Then
_RemoveEventHandler(dependencyObject)
End If
Parameter(dependencyObject).Command = CType(args.NewValue, ICommand)
_AttachEventHandler(dependencyObject)
End Sub
Public Shared Sub EventNameChanged(ByVal dependencyObject As DependencyObject, ByVal args As DependencyPropertyChangedEventArgs)
If Not Parameter.ContainsKey(dependencyObject) Then
Parameter.Add(dependencyObject, CommandParameter.DefaultCP)
End If
End Sub
#End Region
#Region "Helper"
Private Shared Sub _RemoveEventHandler(ByVal dependencyObject As DependencyObject)
If dependencyObject Is Nothing Then
Throw New ArgumentNullException("DependencyObject is null.")
End If
If Not Parameter.ContainsKey(dependencyObject) Then
Exit Sub
End If
Dim param As CommandParameter = Parameter(dependencyObject)
If param.Callback Is Nothing Then
Throw New InvalidProgramException("Cannot remove Callback. Callback is null.")
End If
Dim eventInfo As EventInfo = dependencyObject.GetType().GetEvent(param.EventName)
If eventInfo Is Nothing Then
Throw New InvalidProgramException(String.Format("Cannot find an event with the name <{0}>", param.EventName))
End If
eventInfo.RemoveEventHandler(dependencyObject, param.Callback)
End Sub
Private Shared Sub _AttachEventHandler(ByVal dependencyObject)
If dependencyObject Is Nothing Then
Throw New ArgumentNullException("DependencyObject is null")
End If
If Not Parameter.ContainsKey(dependencyObject) Then
Exit Sub
End If
Dim param As CommandParameter = Parameter(dependencyObject)
If param.Command Is Nothing Or String.IsNullOrEmpty(param.EventName) Then
Exit Sub
End If
Dim eventInfo As EventInfo = dependencyObject.GetType.GetEvent(param.EventName)
If eventInfo Is Nothing Then
Throw New InvalidProgramException(String.Format("Cannot find an event with the name <{0}>", param.EventName))
End If
eventInfo.AddEventHandler(dependencyObject, param.Callback)
End Sub
Private Shared Sub _CommandExecutAction(ByVal parameter As CommandParameter)
parameter.Command.Execute(Nothing)
End Sub
Private Shared Function _CreateHandler(ByVal eventInfo As EventInfo, ByVal method As Action) As [Delegate]
If eventInfo Is Nothing Then
Throw New ArgumentNullException("EventInfo is null")
End If
If method Is Nothing Then
Throw New ArgumentNullException("Action-method is null")
End If
Dim handlerType = eventInfo.EventHandlerType
Dim eventParams = handlerType.GetMethod("Invoke").GetParameters()
Dim parameters = eventParams.[Select](Function(p) System.Linq.Expressions.Expression.Parameter(p.ParameterType, "x"))
Dim body = System.Linq.Expressions.Expression.[Call](System.Linq.Expressions.Expression.Constant(method), method.[GetType]().GetMethod("Invoke"))
Dim lambda = System.Linq.Expressions.Expression.Lambda(body, parameters.ToArray())
Return [Delegate].CreateDelegate(handlerType, lambda.Compile(), "Invoke", False)
End Function
#End Region
#Region "INIT"
Public Sub New()
Parameter = New Dictionary(Of DependencyObject, CommandParameter)()
End Sub
#End Region
End Class
But now I have the problem, that the GetValue() and SetValue()-methods are not available. Any ideas?
Thank you for your help..

Answer 1

An AttachedCommandBehaviour ain't much more than an dependency property of type ICommand, which hookes some events.
Check out Dr. WPFs VB-snippets that includes snippets for dependency properties.
If you use the one that includes a property changed handler, you can use this handler to hook the events you want. In the event handler, you call the attached command.
If you still can't make it work, please post some code.