Why would GetWaitEvent not return a handle?

Hi, me again, I’m splitting my questions into different topics to keep the board cleaner and easier for people to search!

In Local Network Monitor Api C# samples, GetWaitEvent is declared to return a bool, and in the monitor sample it is used as follows:

if (NtTdiApi.GetWaitEvent(hDriver))

{

NtTdiApi.WaitForData( hDriver, 0xFFFFFFFF/*INFINITE*/ );

}

else

{

System.Threading.Thread.Sleep( 1000 );

}

Under what circumstances would GetWaitEvent not return a handle, and cause this ‘else’ block to execute?

Many thanks!