Question

I have the following code:

private static object _dbLock = new object();

public static void LoadData()
{
   lock (_dbLock)
   {
      //Load data from the database
   }
}

public static string ReadData(Guid key)
{
   lock (_dbLock)
   {
      //Lookup key in data and return value
   }
}

I don’t want to allow people to read the data while it’s being loaded from the database, thus I put a lock in ReadData. However, right now if multiple people call ReadData at the same time, only one call can run at once.

Is there a way I can allow simultaneous calls to ReadData but block readers when LoadData is being run?

Answer 1

The ReaderWriterLock and ReaderWriterLockSlim classes support that use case. Use the ‘Slim’ version unless you need pre-3.5 support.

private static ReaderWriterLockSlim _cacheLock = new ReaderWriterLockSlim();

public static void LoadData()
{
    _cacheLock.EnterWriteLock();
    try
    {
        // Load data from the database
    }
    finally
    {
        _cacheLock.ExitWriteLock();
    }
}

public static string ReadData(Guid key)
{
    _cacheLock.EnterReadLock();
    try
    {
        // Lookup key in data and return value
    }
    finally
    {
        _cacheLock.ExitReadLock();
    }
}