How can I set the ProcessorAffinity of a thread?

I know that I can use ProcessThread.ProcessAffinity. But I didn't found an
answer how I can map a ProcessThread to a Thread (they don't seem to be the
same). Because I can not set the affinity of the thread when creating it
does .NET find the best solution for me if I have a multi processor system?

I tried the following code to set the affinity but I can not be sure that is
working. How can I check that the thread is really using another CPU?
ProcessThread.ProcessAffinity allows me only to set the affinity but not to
get it :( I would like to create another application just for checking the
threads....

Hope you have an answer for me....
int id = AppDomain.GetCurrentThreadId();

Process process = Process.GetCurrentProcess();

foreach( ProcessThread processThread in process.Threads )

{

if( processThread.Id == id )

{

processThread.ProcessorAffinity = new IntPtr( processorAffinity );

}

}