IAccessible: Code converted from C# not work

[FL4SHC0D3R]

I converted the code following of C#.NET to VB.NET but he not work as the C#, and is same code! but in VB.NET. I already did several changes but until now nothing solved. Someone could help me? Thank in advance.

Here is the code:
PS: Imports Accessibility reference for the project.

Imports Accessibility
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Runtime.InteropServices
Imports System.Text
Imports System.Threading.Tasks
Imports System.Windows.Forms

Public Class Form1

    Inherits Form

    Private Enum SystemEvents As UInteger

        EVENT_OBJECT_FOCUS = &H8005
        EVENT_OBJECT_NAMECHANGE = &H800C
        EVENT_OBJECT_VALUECHANGE = &H800E

    End Enum

    Private Const WINEVENT_OUTOFCONTEXT As UInteger = &H0
    Shared iAccessible As IAccessible
    Shared ChildId As Object
    Private Shared Value As String

#Region "APIs"

    <DllImport("oleacc.dll")> _
    Public Shared Function WindowFromAccessibleObject(pacc As IAccessible, ByRef phwnd As IntPtr) As UInteger
    End Function

    <DllImport("oleacc.dll")> _
    Private Shared Function AccessibleObjectFromEvent(hwnd As IntPtr, dwObjectID As UInteger, dwChildID As UInteger, ByRef ppacc As IAccessible, <MarshalAs(UnmanagedType.Struct)> ByRef pvarChild As Object) As IntPtr
    End Function

    <DllImport("user32.dll")> _
    Private Shared Function SetWinEventHook(eventMin As UInteger, eventMax As UInteger, hmodWinEventProc As IntPtr, lpfnWinEventProc As WinEventDelegate, idProcess As UInteger, idThread As UInteger, _
            dwFlags As UInteger) As IntPtr
    End Function

    Private Delegate Sub WinEventDelegate(hWinEventHook As IntPtr, eventType As UInteger, hwnd As IntPtr, idObject As UInteger, idChild As UInteger, dwEventThread As UInteger, _
        dwmsEventTime As UInteger)

#End Region

    Private dEvent As WinEventDelegate
    Private pHook As IntPtr
    Private i As Integer = 0


    Public Sub New()
        InitializeComponent()

        dEvent = AddressOf Me.WinEvent

        pHook = SetWinEventHook(CUInt(SystemEvents.EVENT_OBJECT_FOCUS), CUInt(SystemEvents.EVENT_OBJECT_VALUECHANGE), IntPtr.Zero, dEvent, CUInt(0), CUInt(0), _
            WINEVENT_OUTOFCONTEXT)
    End Sub


    <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
    Public Shared Function GetClassName(hWnd As IntPtr, lpClassName As StringBuilder, nMaxCount As Integer) As Integer
    End Function

    Public Shared Function GetWindowClassName(hWnd As IntPtr) As String
        Dim buffer As New StringBuilder(128)

        GetClassName(hWnd, buffer, buffer.Capacity)

        Return buffer.ToString()
    End Function


    Public Shared Function GetControlHandlerFromEvent(hWnd As IntPtr, idObject As UInteger, idChild As UInteger) As IntPtr
        Dim handler As IntPtr = IntPtr.Zero
        handler = AccessibleObjectFromEvent(hWnd, idObject, idChild, iAccessible, ChildId)

        Return handler
    End Function

    <DllImport("user32.dll")> _
    Private Shared Function GetForegroundWindow() As IntPtr
    End Function


    Public Shared Function Gettext() As String
        If iAccessible IsNot Nothing AndAlso ChildId IsNot Nothing Then
            If GetWindowClassName(GetForegroundWindow()) = "Chrome_WidgetWin_1" Then

                Return iAccessible.get_accValue(ChildId)
            End If
        End If

        Return ""
    End Function

    Private Sub WinEvent(hWinEventHook As IntPtr, eventType As UInteger, hWnd As IntPtr, idObject As UInteger, idChild As UInteger, dwEventThread As UInteger, _
        dwmsEventTime As UInteger)

        If eventType = CUInt(SystemEvents.EVENT_OBJECT_NAMECHANGE) Then

            If Value <> Gettext() AndAlso Gettext() <> "" Then

                Value = Gettext()
            End If
            i += 1
            Console.WriteLine("Object" + i)
            GetControlHandlerFromEvent(hWnd, idObject, idChild)

            Console.WriteLine(Gettext())
            TextBox1.Text += Value & vbNewLine

        End If
    End Sub

End Class

[Accessiblesoft]

I saw a couple things wrong in the example.

Here is a working sample for you.

Imports Accessibility
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Runtime.InteropServices
Imports System.Text
Imports System.Threading.Tasks
Imports System.Windows.Forms

Public Class Form1
    Inherits Form
    Const S_OK As Int32 = 0
    Const WINEVENT_OUTOFCONTEXT As Int32 = 0
    Const EVENT_MIN As Int32 = 1
    Const EVENT_MAX As Int32 = 2147483647
    Private Declare Function apiAccessibleObjectFromEvent Lib "oleacc" Alias "AccessibleObjectFromEvent" (ByVal hwnd As Int32, ByVal dwId As Int32, ByVal dwChildId As Int32, ByRef ppacc As Global.Accessibility.IAccessible, ByRef pvarChild As Object) As Int32
    Private Declare Function apiSetWinEventHook Lib "user32" Alias "SetWinEventHook" (ByVal eventMin As Int32, ByVal eventMax As Int32, ByVal hmodWinEventProc As Int32, ByVal pfnWinEventProc As EventFuncDelegate, ByVal idProcess As Int32, ByVal idThread As Int32, ByVal dwFlags As Int32) As Int32
    Private Declare Function apiUnhookWinEvent Lib "user32" Alias "UnhookWinEvent" (ByVal lHandle As Int32) As Int32
    <DllImport("user32.dll")> _
    Private Shared Function GetForegroundWindow() As IntPtr
    End Function
    <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
    Public Shared Function GetClassName(hWnd As IntPtr, lpClassName As StringBuilder, nMaxCount As Integer) As Integer
    End Function
    <System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.FunctionPtr)> Private dEventFunc As EventFuncDelegate
    Private Delegate Function EventFuncDelegate(ByVal HookHandle As Int32, ByVal LEvent As Int32, ByVal hwnd As Int32, ByVal idObject As Int32, ByVal idChild As Int32, ByVal idEventThread As Int32, ByVal dwmsEventTime As Int32) As Int32
    Private pHook As IntPtr = IntPtr.Zero
    Private valu As String = ""

    Private Enum SystemEvents As Int32
        EVENT_OBJECT_FOCUS = &H8005
        EVENT_OBJECT_NAMECHANGE = &H800C
        EVENT_OBJECT_VALUECHANGE = &H800E
    End Enum

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        dEventFunc = New EventFuncDelegate(AddressOf WinEventFunc)
        pHook = apiSetWinEventHook(EVENT_MIN, EVENT_MAX, 0, dEventFunc, 0, 0, WINEVENT_OUTOFCONTEXT)
    End Sub
    Private Sub Form1_FormClosed(sender As Object, e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
        apiUnhookWinEvent(pHook) 'important to close the hook, or you could/will get intermittent results when reloading
    End Sub

    Private Function WinEventFunc(ByVal eHandle As Int32, ByVal lEvent As Int32, ByVal hWnd As Int32, ByVal objId As Int32, ByVal childId As Int32, ByVal eThreadId As Int32, ByVal eTime As Int32) As Int32

        'exit here if not the window you want
        'If GetWindowClassName(GetForegroundWindow()) <> "Chrome_WidgetWin_1" Then Return 0

        If lEvent = SystemEvents.EVENT_OBJECT_NAMECHANGE Then
            Dim iacc As Global.Accessibility.IAccessible = Nothing
            Dim hAcc As IntPtr = apiAccessibleObjectFromEvent(hWnd, objId, childId, iacc, childId)
            If hAcc = S_OK Then
                valu = iacc.accName(childId)



                'TODO we really should not be doing much extensive code here in the win event function.  You can however setup an event with handler to fire from here, that way the function is not delayed, or frozen in an infinite loop
                TextBox1.Text = valu



                'release resources
                iacc = Nothing : childId = Nothing
            End If
        End If
        Return 0
    End Function

    Public Function GetWindowClassName(hWnd As IntPtr) As String
        Dim buffer As New StringBuilder(128)
        GetClassName(hWnd, buffer, buffer.Capacity)
        Return buffer.ToString()
    End Function


End Class

Please find what was wrong with your example and post the reason why here.

[FL4SHC0D3R]

I saw a couple things wrong in the example.

Here is a working sample for you.

Imports Accessibility
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Linq
Imports System.Runtime.InteropServices
Imports System.Text
Imports System.Threading.Tasks
Imports System.Windows.Forms

Public Class Form1
    Inherits Form
    Const S_OK As Int32 = 0
    Const WINEVENT_OUTOFCONTEXT As Int32 = 0
    Const EVENT_MIN As Int32 = 1
    Const EVENT_MAX As Int32 = 2147483647
    Private Declare Function apiAccessibleObjectFromEvent Lib "oleacc" Alias "AccessibleObjectFromEvent" (ByVal hwnd As Int32, ByVal dwId As Int32, ByVal dwChildId As Int32, ByRef ppacc As Global.Accessibility.IAccessible, ByRef pvarChild As Object) As Int32
    Private Declare Function apiSetWinEventHook Lib "user32" Alias "SetWinEventHook" (ByVal eventMin As Int32, ByVal eventMax As Int32, ByVal hmodWinEventProc As Int32, ByVal pfnWinEventProc As EventFuncDelegate, ByVal idProcess As Int32, ByVal idThread As Int32, ByVal dwFlags As Int32) As Int32
    Private Declare Function apiUnhookWinEvent Lib "user32" Alias "UnhookWinEvent" (ByVal lHandle As Int32) As Int32
    <DllImport("user32.dll")> _
    Private Shared Function GetForegroundWindow() As IntPtr
    End Function
    <DllImport("user32.dll", CharSet:=CharSet.Auto)> _
    Public Shared Function GetClassName(hWnd As IntPtr, lpClassName As StringBuilder, nMaxCount As Integer) As Integer
    End Function
    <System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.FunctionPtr)> Private dEventFunc As EventFuncDelegate
    Private Delegate Function EventFuncDelegate(ByVal HookHandle As Int32, ByVal LEvent As Int32, ByVal hwnd As Int32, ByVal idObject As Int32, ByVal idChild As Int32, ByVal idEventThread As Int32, ByVal dwmsEventTime As Int32) As Int32
    Private pHook As IntPtr = IntPtr.Zero
    Private valu As String = ""

    Private Enum SystemEvents As Int32
        EVENT_OBJECT_FOCUS = &H8005
        EVENT_OBJECT_NAMECHANGE = &H800C
        EVENT_OBJECT_VALUECHANGE = &H800E
    End Enum

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        dEventFunc = New EventFuncDelegate(AddressOf WinEventFunc)
        pHook = apiSetWinEventHook(EVENT_MIN, EVENT_MAX, 0, dEventFunc, 0, 0, WINEVENT_OUTOFCONTEXT)
    End Sub
    Private Sub Form1_FormClosed(sender As Object, e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
        apiUnhookWinEvent(pHook) 'important to close the hook, or you could/will get intermittent results when reloading
    End Sub

    Private Function WinEventFunc(ByVal eHandle As Int32, ByVal lEvent As Int32, ByVal hWnd As Int32, ByVal objId As Int32, ByVal childId As Int32, ByVal eThreadId As Int32, ByVal eTime As Int32) As Int32

        'exit here if not the window you want
        'If GetWindowClassName(GetForegroundWindow()) <> "Chrome_WidgetWin_1" Then Return 0

        If lEvent = SystemEvents.EVENT_OBJECT_NAMECHANGE Then
            Dim iacc As Global.Accessibility.IAccessible = Nothing
            Dim hAcc As IntPtr = apiAccessibleObjectFromEvent(hWnd, objId, childId, iacc, childId)
            If hAcc = S_OK Then
                valu = iacc.accName(childId)



                'TODO we really should not be doing much extensive code here in the win event function.  You can however setup an event with handler to fire from here, that way the function is not delayed, or frozen in an infinite loop
                TextBox1.Text = valu



                'release resources
                iacc = Nothing : childId = Nothing
            End If
        End If
        Return 0
    End Function

    Public Function GetWindowClassName(hWnd As IntPtr) As String
        Dim buffer As New StringBuilder(128)
        GetClassName(hWnd, buffer, buffer.Capacity)
        Return buffer.ToString()
    End Function


End Class

Please find what was wrong with your example and post the reason why here.

Dear friend,

Thank you very much for your answer. It works fine! Thank you!
I am parsing the errors...

[Accessiblesoft]

Nice, you are welcome.

[Accessiblesoft]

As a bonus follow up read you can also access these events through UIA(user interface automation).
In this method you subscribe to the events rather than set the hook.

There are differences between the two, so you have to know which one is appropriate for the circumstance.

Here is a quick example of how to DETECT the focus event. I say detect because lengthy code should not be executed within the procedure that could delay or freeze in an infinite loop. Example a system event that fires your code that causes the same system event to fire over again, will loop infinitely or cause memory bugs.

'import .net reference to automation, ie  UIAutomationClient and UIAutomationTypes
Imports System.Windows.Automation

Public Class Form1

    Public focHandler As AutomationFocusChangedEventHandler = Nothing

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        SubscribeToFocusChange()
    End Sub

    Private Sub Form1_FormClosed(sender As Object, e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
        UnsubscribeFocusChange()
    End Sub

    Public Sub SubscribeToFocusChange()
        Try
            focHandler = New AutomationFocusChangedEventHandler(AddressOf OnFocusChanged)
            Automation.AddAutomationFocusChangedEventHandler(focHandler)
        Catch ex As Exception
        End Try
    End Sub

    Public Sub UnsubscribeFocusChange()
        Try
            Automation.RemoveAutomationFocusChangedEventHandler(focHandler)
        Catch ex As Exception
        End Try
    End Sub

    Private Sub OnFocusChanged(ByVal src As Object, ByVal e As AutomationFocusChangedEventArgs)

        'detect focus event here
        Beep()

    End Sub

End Class

[FL4SHC0D3R]

As a bonus follow up read you can also access these events through UIA(user interface automation).
In this method you subscribe to the events rather than set the hook.

There are differences between the two, so you have to know which one is appropriate for the circumstance.

Here is a quick example of how to DETECT the focus event. I say detect because lengthy code should not be executed within the procedure that could delay or freeze in an infinite loop. Example a system event that fires your code that causes the same system event to fire over again, will loop infinitely or cause memory bugs.

'import .net reference to automation, ie  UIAutomationClient and UIAutomationTypes
Imports System.Windows.Automation

Public Class Form1

    Public focHandler As AutomationFocusChangedEventHandler = Nothing

    Private Sub Form1_Load(sender As System.Object, e As System.EventArgs) Handles MyBase.Load
        SubscribeToFocusChange()
    End Sub

    Private Sub Form1_FormClosed(sender As Object, e As System.Windows.Forms.FormClosedEventArgs) Handles Me.FormClosed
        UnsubscribeFocusChange()
    End Sub

    Public Sub SubscribeToFocusChange()
        Try
            focHandler = New AutomationFocusChangedEventHandler(AddressOf OnFocusChanged)
            Automation.AddAutomationFocusChangedEventHandler(focHandler)
        Catch ex As Exception
        End Try
    End Sub

    Public Sub UnsubscribeFocusChange()
        Try
            Automation.RemoveAutomationFocusChangedEventHandler(focHandler)
        Catch ex As Exception
        End Try
    End Sub

    Private Sub OnFocusChanged(ByVal src As Object, ByVal e As AutomationFocusChangedEventArgs)

        'detect focus event here
        Beep()

    End Sub

End Class

Thank you very much @Accessiblesoft!, I will see example above, about how works using IUIAutomation interface.

I have a small example that use IUIAutomation interface for retrieve infos from elements window, these example retrieve the active url from Google Chrome. See:

Imports System.Drawing
Imports System.ComponentModel
Imports System.Windows.Forms
Imports System.Runtime.InteropServices
Imports System.Collections.Generic
Imports System.Data
Imports System.Diagnostics
Imports System.Windows.Automation

Public Class Form1

    Public Shared Function GetChromeUrl(process As Process) As String
        Dim out_url As String = Nothing
        If process Is Nothing Then
            out_url = Nothing
        ElseIf process.MainWindowHandle = IntPtr.Zero Then
            out_url = Nothing
        Else
            Dim element As AutomationElement = AutomationElement.FromHandle(process.MainWindowHandle)
            If element Is Nothing Then
                Return Nothing
            End If
            Dim conditions As Condition = New AndCondition(New PropertyCondition(AutomationElement.ProcessIdProperty, process.Id), New PropertyCondition(AutomationElement.IsControlElementProperty, True), New PropertyCondition(AutomationElement.IsContentElementProperty, True), New PropertyCondition(AutomationElement.ControlTypeProperty, ControlType.Edit))
            Dim elementx As AutomationElement = element.FindFirst(TreeScope.Descendants, conditions)
            out_url = TryCast(DirectCast(elementx.GetCurrentPattern(ValuePattern.Pattern), ValuePattern).Current.Value, String)
        End If
        Return out_url
    End Function

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click

        For Each process__1 As Process In Process.GetProcessesByName("chrome")
            Dim url As String = GetChromeUrl(process__1)
            If url Is Nothing Then
                Continue For
            End If
            MessageBox.Show(url)
        Next

    End Sub
End Class

[Accessiblesoft]

Very good. Not bad, but sometimes you will want to check if the property is available first. In some cases it does not matter, while in a broader application it will.

Here is a function to retrieve an element value if it has one exposed:

    Public Function GetUIAValue(ByVal el As AutomationElement) As String
        If el Is Nothing Then Return ""
        Dim val As String = ""
        Try
            Dim ob As Object = Nothing
            ob = el.GetCurrentPropertyValue(AutomationElement.IsValuePatternAvailableProperty, True)
            If ob IsNot AutomationElement.NotSupported Then
                Dim vp As Object = Nothing
                Try
                    el.TryGetCurrentPattern(ValuePattern.Pattern, vp)
                    If vp IsNot Nothing Then val = TryCast(vp, ValuePattern).Current.Value
                Catch ex As Exception
                End Try
            End If
            ob = Nothing
        Catch ex As Exception
        End Try
        Return val
    End Function

Tip: Some elements may be "custom type" and return "not supported", and in those cases you need to bypass the check of availability, and just check it with an error catch ready in case it throws an error.

[FL4SHC0D3R]

Very good. Not bad, but sometimes you will want to check if the property is available first. In some cases it does not matter, while in a broader application it will.

Here is a function to retrieve an element value if it has one exposed:

    Public Function GetUIAValue(ByVal el As AutomationElement) As String
        If el Is Nothing Then Return ""
        Dim val As String = ""
        Try
            Dim ob As Object = Nothing
            ob = el.GetCurrentPropertyValue(AutomationElement.IsValuePatternAvailableProperty, True)
            If ob IsNot AutomationElement.NotSupported Then
                Dim vp As Object = Nothing
                Try
                    el.TryGetCurrentPattern(ValuePattern.Pattern, vp)
                    If vp IsNot Nothing Then val = TryCast(vp, ValuePattern).Current.Value
                Catch ex As Exception
                End Try
            End If
            ob = Nothing
        Catch ex As Exception
        End Try
        Return val
    End Function

Tip: Some elements may be "custom type" and return "not supported", and in those cases you need to bypass the check of availability, and just check it with an error catch ready in case it throws an error.

@Accessiblesoft,

very useful also this function above!, changing access modifier for Shared, I adjusted she to my previous example and worked very well!

See:

out_url = GetUIAValue(elementx)