how to stop change of objects in collection using c#.

Question

how to stop change of objects in collection using c#.

my object contains multiple collection. during serialization i am getting exception of Collection was modified; enumeration operation may not execute.

At time of serialization only i wants to control change of collection.

i use lock(this) and lock(SyncRoot) both are not working fine.

any alternate option for controlling changing behavior of collection during serialization only.