The IsBlocked property returns True if the specified control
is blocked performing an operation. Because the Windows Sockets API
only permits one blocking operation per thread of execution, this
property can be used to ensure that another blocking operation is not
in progress at the time.
If this property returns False, this means there are no blocking
operations on the current thread at that time. If the property returns
True, this tells you that you the control is already performing a
blocking operation.