Question

我有连接映射类。我需要通过索引访问_connections并实施RemoveAt(indx)方法。

类别：

public class ConnectionMapping<T>
{
    private readonly Dictionary<T, HashSet<string>> _connections = new Dictionary<T, HashSet<string>>();

    public int Count
    {
        get
        {
            return _connections.Count;
        }
    }
    public void Add(T key, string connectionId)
    {
        lock (_connections)
        {
            HashSet<string> connections;
            if (!_connections.TryGetValue(key, out connections))
            {
                connections = new HashSet<string>();
                _connections.Add(key, connections);
            }

            lock (connections)
            {
                connections.Add(connectionId);
            }
        }
    }
    public void Remove(T key, string connectionId)
    {
        lock (_connections)
        {
            HashSet<string> connections;
            if (!_connections.TryGetValue(key, out connections))
            {
                return;
            }

            lock (connections)
            {
                connections.Remove(connectionId);

                if (connections.Count == 0)
                {
                    _connections.Remove(key);
                }
            }
        }
    }
    public IEnumerable<string> GetConnections(T key)
    {
        HashSet<string> connections;
        if (_connections.TryGetValue(key, out connections))
        {
            return connections;
        }
        return Enumerable.Empty<string>();
    }
}

示例：

_connections.RemoveAt(0); 
_connections[0].Value = _value, 
_connections[0].Key = _key;

如何修改类来实现这个目标？

Answer 1

字典不保留其元素的任何顺序，因此无法知道要删除哪一个。您只能使用Remove(TKey key)。

或者您可以使用OrderedDictionary

Represents a collection of key/value pairs that are accessible by the key or index.

RemoveAt已经实施 OrderedDictionary.RemoveAt

Answer 2

字典不维护顺序，因此在给定索引处没有一致的项目概念。考虑从KeyedCollection<TKey, TValue>继承：

using System.Collections.ObjectModel;

public class ConnectionMapping<T>
{
    private class Mapping
    {
        public T Key;
        public HashSet<string> Items;
    }

    private class ConnectionsCollection : KeyedCollection<T, Mapping>
    {
        protected override T GetKeyForItem(Mapping item)
        {
            return item.Key;
        }
    }

    private readonly ConnectionsCollection _connections = new ConnectionsCollection();

    /// Implementation of various collection methods, Add, RemoveAt, etc.

    public void RemoveAt(int index)
    {
        lock(_connections)
        {
            _connections.RemoveAt(index);
        }
    }
}

您可能希望在ConnectionsCollection上添加一些辅助方法，以进行类似字典的访问（例如TryGetValue）。您目前的锁定是不够的。您还需要锁定GetConnections。不要从那里返回实际的集合，返回connections。

的副本

如何实现自定义集合类的索引器和RemoveAt方法？

2 个答案: