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c#listthread-safety
Jay
Jay

Reputation: 1003

Concurrent Thread-Safe List access and modification

What I want to be able to do is to access a List on multiple threads. This is thread safe, so I can just do it without worries. The only problem is that occasionally, I must modify the List. So, I want to prevent other threads from using the List only when it is being modified.

This is what I'm thinking, is there a better way?

volatile bool isReading = false;
volatile bool isWriting = false;
object o = new object();
public void StartRead()
{
    lock (o)
    {
        while (isWriting || isReading) ;
        isReading = true;
    }
}
public void StopRead()
{
    isReading = false;
}
public void StartWrite()
{
    lock (o)
    {
        while (isReading) ;
        isWriting = true;
    }
}
public void StopWrite()
{
    isWriting = false;
}

Upvotes: 1

Views: 1221

Answers (1)

Gjeltema
Gjeltema

Reputation: 4166

A better solution would be to use a ReaderWriterLockSlim. This will let you have many readers at the same time, but only lock it when you have a writer.

http://msdn.microsoft.com/en-us/library/system.threading.readerwriterlockslim.aspx

This really depends on just how much contention there is for the lock though. In low-contention situations, a lock will perform similarly to the ReaderWriterLockSlim - reference When is ReaderWriterLockSlim better than a simple lock?.

There's many possible solutions to this question, depending on a lot of specifics about how it's being used. But, in the simplistic "taken at face value" case, a ReaderWriterLockSlim is a decent solution. If it doesn't work for you after profiling performance, then other solutions may be needed that accommodate your specific usage scenarios.

Upvotes: 3

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