Я все еще не понял, как заставить его просто выделять элемент панели задач, а не мигать. Вот код, который сработал для меня (я чувствую себя довольно глупо из-за того, что пропущено значение счетчика до 1, надеюсь, это сэкономит кому-то еще время).
Public Structure FLASHWINFO
Public cbSize As UInt32
Public hwnd As IntPtr
Public dwFlags As UInt32
Public uCount As UInt32
Public dwTimeout As UInt32
End Structure
Private Declare Function FlashWindowEx Lib "user32.dll" (ByRef pfwi As FLASHWINFO) As Boolean
Private Const FLASHW_STOP As UInt32 = 0
Private Const FLASHW_CAPTION As UInt32 = 1
Private Const FLASHW_TRAY As UInt32 = 2
Private Const FLASHW_ALL As UInt32 = 3
Private Const FLASHW_TIMER As UInt32 = 4
Private Const FLASHW_TIMERNOFG As UInt32 = 12
Public Shared Sub Flash(ByRef thisForm As Form)
Dim flash As New FLASHWINFO With {
.cbSize = System.Runtime.InteropServices.Marshal.SizeOf(flash),
.hwnd = thisForm.Handle,
.dwFlags = FLASHW_TRAY Or FLASHW_TIMERNOFG,
.uCount = 1}
'Leaving out .dwCount seems to work just fine for me, the uCount above keeps it from flashing
FlashWindowEx(flash)
End Sub