Dictionary源码解析（未完）

private void Insert(TKey key, TValue value, bool add)
{
    if (key == null)
    {
        ThrowHelper.ThrowArgumentNullException(ExceptionArgument.key);
    }
    if (this.buckets == null)
    {
        this.Initialize(0);
    }
    int num = this.comparer.GetHashCode(key) & 2147483647;
    int num2 = num % this.buckets.Length;
    for (int i = this.buckets[num2]; i >= 0; i = this.entries[i].next)
    {
        if (this.entries[i].hashCode == num && this.comparer.Equals(this.entries[i].key, key))
        {
            if (add)
            {
                ThrowHelper.ThrowArgumentException(ExceptionResource.Argument_AddingDuplicate);
            }
            this.entries[i].value = value;
            this.version++;
            return;
        }
    }
    int num3;
    if (this.freeCount > 0)
    {
        num3 = this.freeList;
        this.freeList = this.entries[num3].next;
        this.freeCount--;
    }
    else
    {
        if (this.count == this.entries.Length)
        {
            this.Resize();
            num2 = num % this.buckets.Length;
        }
        num3 = this.count;
        this.count++;
    }
    this.entries[num3].hashCode = num;
    this.entries[num3].next = this.buckets[num2];
    this.entries[num3].key = key;
    this.entries[num3].value = value;
    this.buckets[num2] = num3;
    this.version++;
}

1.如果传入的是字符串的话，GetHashCode的算法和字符串的长度成正比。这导致了有时这个O(1)的时间复杂度在具体使用时可能比log(n)复杂度的还有久。

2. 如果直接重写equals方法，可能会对值类型装箱。这样就不能体现值类型在调用完就立刻回收，不会增加GC压力的这个好处了。

3.memecached

解决增加节点后的缓存失效问题，hash consistence算法。

 http://blog.csdn.net/sparkliang/article/details/5279393

3.线程安全