什么是 C# 中 Hashtable 实现的示例？
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What is an example of a Hashtable implementation in C#?
提问by Arec Barrwin
I realize C# and .NET in general already has the Hashtable and Dictionary classes.
我意识到 C# 和 .NET 通常已经有 Hashtable 和 Dictionary 类。
Can anyone demonstrate in C# an implementation of a Hashtable?
任何人都可以在 C# 中演示 Hashtable 的实现吗？
Update:To clarify, I'm not ncessarily looking for a complete implementation, just an example of the core features of a hashtable (i.e. add,remove, find by key).
更新：澄清一下，我不一定要寻找完整的实现，只是哈希表核心功能的一个示例（即添加、删除、按键查找）。
采纳答案by Luke Quinane
There is also the Mono version of the class libraries of course:
当然还有 Mono 版本的类库：
回答by Jon Skeet
Have you looked at the C5 collections? You can download the sourcewhich includes a hash table.
回答by Ward Werbrouck
You can see how the .NET Hashtable is implemented (for example in C#) using reflector
您可以看到 .NET Hashtable 是如何使用反射器实现的（例如在 C# 中）
回答by Paul Dixon
回答by RichardOD
Long after the question has been asked, so I don't expect to earn much rep. However I decided it would be fun to write my own very basic example (in less than 90 lines of code):
在提出这个问题很久之后，所以我不希望获得太多代表。但是，我认为编写自己的非常基本的示例（不到 90 行代码）会很有趣：
public struct KeyValue<K, V>
{
public K Key { get; set; }
public V Value { get; set; }
}
public class FixedSizeGenericHashTable<K,V>
{
private readonly int size;
private readonly LinkedList<KeyValue<K,V>>[] items;
public FixedSizeGenericHashTable(int size)
{
this.size = size;
items = new LinkedList<KeyValue<K,V>>[size];
}
protected int GetArrayPosition(K key)
{
int position = key.GetHashCode() % size;
return Math.Abs(position);
}
public V Find(K key)
{
int position = GetArrayPosition(key);
LinkedList<KeyValue<K, V>> linkedList = GetLinkedList(position);
foreach (KeyValue<K,V> item in linkedList)
{
if (item.Key.Equals(key))
{
return item.Value;
}
}
return default(V);
}
public void Add(K key, V value)
{
int position = GetArrayPosition(key);
LinkedList<KeyValue<K, V>> linkedList = GetLinkedList(position);
KeyValue<K, V> item = new KeyValue<K, V>() { Key = key, Value = value };
linkedList.AddLast(item);
}
public void Remove(K key)
{
int position = GetArrayPosition(key);
LinkedList<KeyValue<K, V>> linkedList = GetLinkedList(position);
bool itemFound = false;
KeyValue<K, V> foundItem = default(KeyValue<K, V>);
foreach (KeyValue<K,V> item in linkedList)
{
if (item.Key.Equals(key))
{
itemFound = true;
foundItem = item;
}
}
if (itemFound)
{
linkedList.Remove(foundItem);
}
}
protected LinkedList<KeyValue<K, V>> GetLinkedList(int position)
{
LinkedList<KeyValue<K, V>> linkedList = items[position];
if (linkedList == null)
{
linkedList = new LinkedList<KeyValue<K, V>>();
items[position] = linkedList;
}
return linkedList;
}
}
Here's a little test application:
这是一个小测试应用程序：
static void Main(string[] args)
{
FixedSizeGenericHashTable<string, string> hash = new FixedSizeGenericHashTable<string, string>(20);
hash.Add("1", "item 1");
hash.Add("2", "item 2");
hash.Add("dsfdsdsd", "sadsadsadsad");
string one = hash.Find("1");
string two = hash.Find("2");
string dsfdsdsd = hash.Find("dsfdsdsd");
hash.Remove("1");
Console.ReadLine();
}
It's not the best implementation, but it works for Add, Remove and Find. It uses chainingand a simple modulo algorithm to find the appropriate bucket.
这不是最好的实现，但它适用于添加、删除和查找。它使用链接和简单的模算法来找到合适的桶。
