ConcurrentDictionary是线程安全类，是什么在保证？
内部类
private class Tables
{
internal readonly Node[] m_buckets; // A singly-linked list for each bucket.
internal readonly object[] m_locks // A set of locks, each guarding a section of the table.
……
}
构造函数
internal ConcurrentDictionary(int concurrencyLevel, int capacity, bool growLockArray, IEqualityComparer<TKey> comparer)
{
if (concurrencyLevel < 1)
{
throw new ArgumentOutOfRangeException("concurrencyLevel", GetResource("ConcurrentDictionary_ConcurrencyLevelMustBePositive"));
}
if (capacity < 0)
{
throw new ArgumentOutOfRangeException("capacity", GetResource("ConcurrentDictionary_CapacityMustNotBeNegative"));
}
if (comparer == null) throw new ArgumentNullException("comparer"); // The capacity should be at least as large as the concurrency level. Otherwise, we would have locks that don't guard
// any buckets.
if (capacity < concurrencyLevel)
{
capacity = concurrencyLevel;
} object[] locks = new object[concurrencyLevel];
for (int i = 0; i < locks.Length; i++)
{
locks[i] = new object();
} int[] countPerLock = new int[locks.Length];
Node[] buckets = new Node[capacity];
m_tables = new Tables(buckets, locks, countPerLock, comparer);
……
}
TryAdd内部实现
……
Monitor.Enter(tables.m_locks[lockNo], ref lockTaken);
……
Monitor.Exit(tables.m_locks[lockNo]);
……
实质是维护了一个tables，m_buckets 负责存储，m_locks负责保存锁。至于用哪个bucket，用哪个lock，是有一定的算法，和hash有关。