Memory lock to ensure shared data can be read from by many threads, but only written to by one?

Question

I am trying to write a C# program where values in a list A are checked against a particular value x in a thread. I would like the threads to compare their x values to each of the ones in the list, and if it is not found, I would like them to add their value x to A . The thread will then get a new x from a list in it's private memory, and begin comparing it to the values in A again. The objective of this program is to make A a list of unique values, and contain all of the values of the lists in the threads.

I'm wondering if C# has some native read/write lock that will allow as many threads to read from a single list as possible, but once one starts to write, I would like all of the other threads to wait before attempting to read from the list again.

Also, is there a way I could ensure multiple threads won't attempt to write at the same time? I could see this being an issue if 2+ threads contained the same x value and tried to gain the write lock simultaneously - then added the same value to the list one after another.

Answer 1

I'm wondering if C# has some native read/write lock that will allow as many threads to read from a single list as possible

Yes, use a Reader Writer Lock . That's what it's designed for.

There are two versions of ReaderWriterLock in .net ReaderWriterLock and ReaderWriterLockSlim respectively. Latter one is preferred as it is efficient.