Are some modifiers not supported by SendKeys.SendWait? - windows

Question

I have a code that works perfectly, copying selected text from any windows application pressing CTRL+B.
However, when I change the modifiers that trigger the SendKeys.SendWait("^c") from MOD_CONTROL to MOD_ALT + MOD_SHIFT, the command SendKeys doesn't copy the text from the active window.
So pressing ALT+SHIFT+B still launch the command SendKeys, but the command doesn't copy the selected text to the clipboard.
Is there some incopatibility between the sendkeys command and the modifiers other then MOD_CONTROL?
I have tried registering different hotkeys, and different modifiers for each hotkey: sendkeys works with every hotkey with MOD_CONTROL modifier but doesn't with every hotkey with any other modifiers combination.
Public Class Form1
Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
UnregisterHotKey(Nothing, HotKeyID)
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
RegisterHotKey(Me.Handle, HotKeyID, MOD_CONTROL, VK_b)
End Sub
Private Declare Function GetForegroundWindow Lib "User32" () As IntPtr
Private Declare Function RegisterHotKey Lib "User32.dll" (ByVal hWnd As IntPtr, ByVal ID As Integer, ByVal Modifiers As UInteger, ByVal VK As UInteger) As Boolean
Private Declare Function UnregisterHotKey Lib "User32.dll" (ByVal hWnd As IntPtr, ByVal ID As Integer) As Boolean
Private HotKeyID As Integer = 1
Private Const WM_HOTKEY As Integer = &H312
Private Const MOD_ALT As UInteger = 1
Private Const MOD_CONTROL As UInteger = 2
Private Const MOD_SHIFT As UInteger = 4
Private Const VK_b As UInteger = &H42
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
If m.Msg = WM_HOTKEY Then
Dim Modif As UInteger = (CType(m.LParam, Integer) And &HFFFF)
Dim Key As UInteger = CType(m.LParam, Integer) >> 16
If Key = VK_b And Modif = MOD_CONTROL Then
'Check foregroundwindow has a valid handle
If GetForegroundWindow <> IntPtr.Zero Then
'Send the Ctrl+C command to the active window
SendKeys.SendWait("^c")
End If
End If
Else
MyBase.WndProc(m)
End If
End Sub
End Class
If I change
If Key = VK_b And Modif = MOD_CONTROL Then
'Check foregroundwindow has a valid handle
If GetForegroundWindow <> IntPtr.Zero Then
'Send the Ctrl+C command to the active window
SendKeys.SendWait("^c")
End If
End If
With:
If Key = VK_b And Modif = MOD_ALT + MOD_SHIFT Then
'Check foregroundwindow has a valid handle
If GetForegroundWindow <> IntPtr.Zero Then
'Send the Ctrl+C command to the active window
SendKeys.SendWait("^c")
End If
End If
The command SendKeys.SendWait doesn'nt copy the selected text: can someone give me a clue?
Thank you

Answer 1

At last I managed it to work adding the line:
System.Threading.Thread.Sleep(300)
just before the command SendKeys.SendWait("^c")
It seems that SendKeys have issue with timing and the pause inserted resolve the issue.
So, now this code works:
Public Class Form1
Private Sub Form1_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
UnregisterHotKey(Nothing, HotKeyID)
End Sub
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
RegisterHotKey(Me.Handle, HotKeyID, MOD_ALT + MOD_SHIFT, VK_b)
End Sub
Private Declare Function GetForegroundWindow Lib "User32" () As IntPtr
Private Declare Function RegisterHotKey Lib "User32.dll" (ByVal hWnd As IntPtr, ByVal ID As Integer, ByVal Modifiers As UInteger, ByVal VK As UInteger) As Boolean
Private Declare Function UnregisterHotKey Lib "User32.dll" (ByVal hWnd As IntPtr, ByVal ID As Integer) As Boolean
Private Const WM_HOTKEY As Integer = &H312
Private Const MOD_ALT As UInteger = 1
Private Const MOD_CONTROL As UInteger = 2
Private Const MOD_SHIFT As UInteger = 4
Private Const VK_b As UInteger = 66
Private HotKeyID As Integer = 1
Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
If m.Msg = WM_HOTKEY Then
Dim Modif As UInteger = (CType(m.LParam, Integer) And &HFFFF)
Dim Key As UInteger = CType(m.LParam, Integer) >> 16
If Key = VK_b And Modif = MOD_ALT + MOD_SHIFT Then
'Check foregroundwindow has a valid handle
If GetForegroundWindow <> IntPtr.Zero Then
'Send the Ctrl+C command to the active window
System.Threading.Thread.Sleep(300)
SendKeys.SendWait("^c")
End If
End If
Else
MyBase.WndProc(m)
End If
End Sub
End Class