The following code implements the semaphore using C#, find is there any weekness or bug.

Question

public class Semaphore
{
private object _mutex = new object;
private int _currAvail;
public Semaphore(int capacity)
{
_currAvail = capacity;
}
public void Wait()
{
lock(_mutex)
{
if ( currAvail == 0) Monitor.Wait(_mutex);
_currAvail --;
}
}
public void Signal()
{
lock(_mutex)
{
_currAvail ++;
Monitor.Pulse(_mutex);
}
}
}