This method is similar to the Peek method, but Peek does not modify the Stack.
a null reference (Nothing in Visual Basic) can be pushed onto the Stack as a placeholder, if needed. To distinguish between a null value and the end of the stack, check the Count property or catch the InvalidOperationException, which is thrown when the Stack is empty.
Stack is implemented as a circular buffer. This method is an O(1) operation.
Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)