static extern bool ShutdownBlockReasonCreate(IntPtr hWnd, [MarshalAs(UnmanagedType.LPWStr)] string reason);

Declare Function ShutdownBlockReasonCreate Lib "user32.dll" (ByVal hWnd As IntPtr, <Runtime.InteropServices.MarshalAs(Runtime.InteropServices.UnmanagedType.LPWStr)> ByVal reason As String) As Boolean

if (!ShutdownBlockReasonCreate(handleForShutdownBlocker, UIMessages.GetString("ShutdownBlockReason"))) {

    log.Error(string.Format("Failed calling ShutdownBlockReasonCreate. Error code: {0}, blocking form handle: {1}", error, handleForShutdownBlocker));