void SetFocus();

Windows allows only one caret per message queue. To add a caret to a control, handle the WM_SETFOCUS message, or the GotFocus event, or override OnGotFocus if you're writing a custom control, and call CreateCaret from the message or event handler. You should also handle WM_KILLFOCUS, LostFocus or OnLostFocus and call DestroyCaret. You will also need to call ShowCaret to make the caret visible, and SetCaretPos to set its position.

static extern IntPtr SetFocus(IntPtr hWnd);

Private Declare Function SetFocus Lib "user32.dll" (ByVal hwnd As IntPtr) As IntPtr

SetFocus(p.MainWindowHandle)

    public const int NIM_SETFOCUS       = 0x00000003;

    public const int NIM_SETFOCUS       = 0x00000003;

private const UInt32 WM_SETFOCUS           = 0x0007;

   WM_SETFOCUS = &H7

WM_SETFOCUS           equ 007h

        public uint bSetFocus;

        public uint bSetFocus;

    SetFocus = 9

    SetFocus = 9

    /// The WM_SETFOCUS message is sent to a window after it has gained the keyboard focus.

    SETFOCUS = 0x0007,

    WM_SETFOCUS = &H7

    WmSetFocus = &H7

    Function OnFocusChangeIS(<MarshalAs(UnmanagedType.IUnknown)> punkObj As [Object], fSetFocus As Int32) As Int32

    Function OnFocusChangeIS(<MarshalAs(UnmanagedType.IUnknown)> punkObj As [Object], fSetFocus As Int32) As Int32

               [MarshalAs (UnmanagedType.Bool)] ref bool fSetFocus);