protected void SetVersion(int v)
{
if (v < 0) {
string msg;
msg = String.Format ("Attempt to set invalid version {0} on Filter {1}", v, Name);
throw new Exception (msg);
}
if (v <= version) {
string msg;
msg = String.Format ("Attempt to re-set version from {0} to {1} on Filter {2}", version, v, Name);
throw new Exception (msg);
}
version = v;
}