在.NET 3.5中似乎没有OrderedDictionary（在System.Collections.Specialized命名空间中）的通用实现。有没有我错过的？
我发现那里的实现提供了功能，但想知道是否/为什么没有开箱即用的通用实现，如果有人知道它是否是.NET 4.0中的东西？
答案 0 :(得分：91)
实现通用OrderedDictionary并不是非常困难，但它不必要地耗费时间，而且坦率地说，这个类对微软来说是一个巨大的疏忽。有多种方法可以实现这一点，但我选择使用KeyedCollection作为内部存储空间。我还选择实现各种方法来排序List<T>的方式，因为它本质上是一个混合的IList和IDictionary。我把这个实现包含在后代中。
这是界面。请注意，它包含System.Collections.Specialized.IOrderedDictionary，这是Microsoft提供的此接口的非泛型版本。
// http://unlicense.org
using System;
using System.Collections.Generic;
using System.Collections.Specialized;
namespace mattmc3.Common.Collections.Generic {
public interface IOrderedDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IOrderedDictionary {
new TValue this[int index] { get; set; }
new TValue this[TKey key] { get; set; }
new int Count { get; }
new ICollection<TKey> Keys { get; }
new ICollection<TValue> Values { get; }
new void Add(TKey key, TValue value);
new void Clear();
void Insert(int index, TKey key, TValue value);
int IndexOf(TKey key);
bool ContainsValue(TValue value);
bool ContainsValue(TValue value, IEqualityComparer<TValue> comparer);
new bool ContainsKey(TKey key);
new IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator();
new bool Remove(TKey key);
new void RemoveAt(int index);
new bool TryGetValue(TKey key, out TValue value);
TValue GetValue(TKey key);
void SetValue(TKey key, TValue value);
KeyValuePair<TKey, TValue> GetItem(int index);
void SetItem(int index, TValue value);
}
}
以下是辅助类的实现：
// http://unlicense.org
using System;
using System.Collections.ObjectModel;
using System.Diagnostics;
using System.Collections;
using System.Collections.Specialized;
using System.Collections.Generic;
using System.Linq;
namespace mattmc3.Common.Collections.Generic {
/// <summary>
/// A dictionary object that allows rapid hash lookups using keys, but also
/// maintains the key insertion order so that values can be retrieved by
/// key index.
/// </summary>
public class OrderedDictionary<TKey, TValue> : IOrderedDictionary<TKey, TValue> {
#region Fields/Properties
private KeyedCollection2<TKey, KeyValuePair<TKey, TValue>> _keyedCollection;
/// <summary>
/// Gets or sets the value associated with the specified key.
/// </summary>
/// <param name="key">The key associated with the value to get or set.</param>
public TValue this[TKey key] {
get {
return GetValue(key);
}
set {
SetValue(key, value);
}
}
/// <summary>
/// Gets or sets the value at the specified index.
/// </summary>
/// <param name="index">The index of the value to get or set.</param>
public TValue this[int index] {
get {
return GetItem(index).Value;
}
set {
SetItem(index, value);
}
}
public int Count {
get { return _keyedCollection.Count; }
}
public ICollection<TKey> Keys {
get {
return _keyedCollection.Select(x => x.Key).ToList();
}
}
public ICollection<TValue> Values {
get {
return _keyedCollection.Select(x => x.Value).ToList();
}
}
public IEqualityComparer<TKey> Comparer {
get;
private set;
}
#endregion
#region Constructors
public OrderedDictionary() {
Initialize();
}
public OrderedDictionary(IEqualityComparer<TKey> comparer) {
Initialize(comparer);
}
public OrderedDictionary(IOrderedDictionary<TKey, TValue> dictionary) {
Initialize();
foreach (KeyValuePair<TKey, TValue> pair in dictionary) {
_keyedCollection.Add(pair);
}
}
public OrderedDictionary(IOrderedDictionary<TKey, TValue> dictionary, IEqualityComparer<TKey> comparer) {
Initialize(comparer);
foreach (KeyValuePair<TKey, TValue> pair in dictionary) {
_keyedCollection.Add(pair);
}
}
#endregion
#region Methods
private void Initialize(IEqualityComparer<TKey> comparer = null) {
this.Comparer = comparer;
if (comparer != null) {
_keyedCollection = new KeyedCollection2<TKey, KeyValuePair<TKey, TValue>>(x => x.Key, comparer);
}
else {
_keyedCollection = new KeyedCollection2<TKey, KeyValuePair<TKey, TValue>>(x => x.Key);
}
}
public void Add(TKey key, TValue value) {
_keyedCollection.Add(new KeyValuePair<TKey, TValue>(key, value));
}
public void Clear() {
_keyedCollection.Clear();
}
public void Insert(int index, TKey key, TValue value) {
_keyedCollection.Insert(index, new KeyValuePair<TKey, TValue>(key, value));
}
public int IndexOf(TKey key) {
if (_keyedCollection.Contains(key)) {
return _keyedCollection.IndexOf(_keyedCollection[key]);
}
else {
return -1;
}
}
public bool ContainsValue(TValue value) {
return this.Values.Contains(value);
}
public bool ContainsValue(TValue value, IEqualityComparer<TValue> comparer) {
return this.Values.Contains(value, comparer);
}
public bool ContainsKey(TKey key) {
return _keyedCollection.Contains(key);
}
public KeyValuePair<TKey, TValue> GetItem(int index) {
if (index < 0 || index >= _keyedCollection.Count) {
throw new ArgumentException(String.Format("The index was outside the bounds of the dictionary: {0}", index));
}
return _keyedCollection[index];
}
/// <summary>
/// Sets the value at the index specified.
/// </summary>
/// <param name="index">The index of the value desired</param>
/// <param name="value">The value to set</param>
/// <exception cref="ArgumentOutOfRangeException">
/// Thrown when the index specified does not refer to a KeyValuePair in this object
/// </exception>
public void SetItem(int index, TValue value) {
if (index < 0 || index >= _keyedCollection.Count) {
throw new ArgumentException("The index is outside the bounds of the dictionary: {0}".FormatWith(index));
}
var kvp = new KeyValuePair<TKey, TValue>(_keyedCollection[index].Key, value);
_keyedCollection[index] = kvp;
}
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator() {
return _keyedCollection.GetEnumerator();
}
public bool Remove(TKey key) {
return _keyedCollection.Remove(key);
}
public void RemoveAt(int index) {
if (index < 0 || index >= _keyedCollection.Count) {
throw new ArgumentException(String.Format("The index was outside the bounds of the dictionary: {0}", index));
}
_keyedCollection.RemoveAt(index);
}
/// <summary>
/// Gets the value associated with the specified key.
/// </summary>
/// <param name="key">The key associated with the value to get.</param>
public TValue GetValue(TKey key) {
if (_keyedCollection.Contains(key) == false) {
throw new ArgumentException("The given key is not present in the dictionary: {0}".FormatWith(key));
}
var kvp = _keyedCollection[key];
return kvp.Value;
}
/// <summary>
/// Sets the value associated with the specified key.
/// </summary>
/// <param name="key">The key associated with the value to set.</param>
/// <param name="value">The the value to set.</param>
public void SetValue(TKey key, TValue value) {
var kvp = new KeyValuePair<TKey, TValue>(key, value);
var idx = IndexOf(key);
if (idx > -1) {
_keyedCollection[idx] = kvp;
}
else {
_keyedCollection.Add(kvp);
}
}
public bool TryGetValue(TKey key, out TValue value) {
if (_keyedCollection.Contains(key)) {
value = _keyedCollection[key].Value;
return true;
}
else {
value = default(TValue);
return false;
}
}
#endregion
#region sorting
public void SortKeys() {
_keyedCollection.SortByKeys();
}
public void SortKeys(IComparer<TKey> comparer) {
_keyedCollection.SortByKeys(comparer);
}
public void SortKeys(Comparison<TKey> comparison) {
_keyedCollection.SortByKeys(comparison);
}
public void SortValues() {
var comparer = Comparer<TValue>.Default;
SortValues(comparer);
}
public void SortValues(IComparer<TValue> comparer) {
_keyedCollection.Sort((x, y) => comparer.Compare(x.Value, y.Value));
}
public void SortValues(Comparison<TValue> comparison) {
_keyedCollection.Sort((x, y) => comparison(x.Value, y.Value));
}
#endregion
#region IDictionary<TKey, TValue>
void IDictionary<TKey, TValue>.Add(TKey key, TValue value) {
Add(key, value);
}
bool IDictionary<TKey, TValue>.ContainsKey(TKey key) {
return ContainsKey(key);
}
ICollection<TKey> IDictionary<TKey, TValue>.Keys {
get { return Keys; }
}
bool IDictionary<TKey, TValue>.Remove(TKey key) {
return Remove(key);
}
bool IDictionary<TKey, TValue>.TryGetValue(TKey key, out TValue value) {
return TryGetValue(key, out value);
}
ICollection<TValue> IDictionary<TKey, TValue>.Values {
get { return Values; }
}
TValue IDictionary<TKey, TValue>.this[TKey key] {
get {
return this[key];
}
set {
this[key] = value;
}
}
#endregion
#region ICollection<KeyValuePair<TKey, TValue>>
void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> item) {
_keyedCollection.Add(item);
}
void ICollection<KeyValuePair<TKey, TValue>>.Clear() {
_keyedCollection.Clear();
}
bool ICollection<KeyValuePair<TKey, TValue>>.Contains(KeyValuePair<TKey, TValue> item) {
return _keyedCollection.Contains(item);
}
void ICollection<KeyValuePair<TKey, TValue>>.CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex) {
_keyedCollection.CopyTo(array, arrayIndex);
}
int ICollection<KeyValuePair<TKey, TValue>>.Count {
get { return _keyedCollection.Count; }
}
bool ICollection<KeyValuePair<TKey, TValue>>.IsReadOnly {
get { return false; }
}
bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item) {
return _keyedCollection.Remove(item);
}
#endregion
#region IEnumerable<KeyValuePair<TKey, TValue>>
IEnumerator<KeyValuePair<TKey, TValue>> IEnumerable<KeyValuePair<TKey, TValue>>.GetEnumerator() {
return GetEnumerator();
}
#endregion
#region IEnumerable
IEnumerator IEnumerable.GetEnumerator() {
return GetEnumerator();
}
#endregion
#region IOrderedDictionary
IDictionaryEnumerator IOrderedDictionary.GetEnumerator() {
return new DictionaryEnumerator<TKey, TValue>(this);
}
void IOrderedDictionary.Insert(int index, object key, object value) {
Insert(index, (TKey)key, (TValue)value);
}
void IOrderedDictionary.RemoveAt(int index) {
RemoveAt(index);
}
object IOrderedDictionary.this[int index] {
get {
return this[index];
}
set {
this[index] = (TValue)value;
}
}
#endregion
#region IDictionary
void IDictionary.Add(object key, object value) {
Add((TKey)key, (TValue)value);
}
void IDictionary.Clear() {
Clear();
}
bool IDictionary.Contains(object key) {
return _keyedCollection.Contains((TKey)key);
}
IDictionaryEnumerator IDictionary.GetEnumerator() {
return new DictionaryEnumerator<TKey, TValue>(this);
}
bool IDictionary.IsFixedSize {
get { return false; }
}
bool IDictionary.IsReadOnly {
get { return false; }
}
ICollection IDictionary.Keys {
get { return (ICollection)this.Keys; }
}
void IDictionary.Remove(object key) {
Remove((TKey)key);
}
ICollection IDictionary.Values {
get { return (ICollection)this.Values; }
}
object IDictionary.this[object key] {
get {
return this[(TKey)key];
}
set {
this[(TKey)key] = (TValue)value;
}
}
#endregion
#region ICollection
void ICollection.CopyTo(Array array, int index) {
((ICollection)_keyedCollection).CopyTo(array, index);
}
int ICollection.Count {
get { return ((ICollection)_keyedCollection).Count; }
}
bool ICollection.IsSynchronized {
get { return ((ICollection)_keyedCollection).IsSynchronized; }
}
object ICollection.SyncRoot {
get { return ((ICollection)_keyedCollection).SyncRoot; }
}
#endregion
}
public class KeyedCollection2<TKey, TItem> : KeyedCollection<TKey, TItem> {
private const string DelegateNullExceptionMessage = "Delegate passed cannot be null";
private Func<TItem, TKey> _getKeyForItemDelegate;
public KeyedCollection2(Func<TItem, TKey> getKeyForItemDelegate)
: base() {
if (getKeyForItemDelegate == null) throw new ArgumentNullException(DelegateNullExceptionMessage);
_getKeyForItemDelegate = getKeyForItemDelegate;
}
public KeyedCollection2(Func<TItem, TKey> getKeyForItemDelegate, IEqualityComparer<TKey> comparer)
: base(comparer) {
if (getKeyForItemDelegate == null) throw new ArgumentNullException(DelegateNullExceptionMessage);
_getKeyForItemDelegate = getKeyForItemDelegate;
}
protected override TKey GetKeyForItem(TItem item) {
return _getKeyForItemDelegate(item);
}
public void SortByKeys() {
var comparer = Comparer<TKey>.Default;
SortByKeys(comparer);
}
public void SortByKeys(IComparer<TKey> keyComparer) {
var comparer = new Comparer2<TItem>((x, y) => keyComparer.Compare(GetKeyForItem(x), GetKeyForItem(y)));
Sort(comparer);
}
public void SortByKeys(Comparison<TKey> keyComparison) {
var comparer = new Comparer2<TItem>((x, y) => keyComparison(GetKeyForItem(x), GetKeyForItem(y)));
Sort(comparer);
}
public void Sort() {
var comparer = Comparer<TItem>.Default;
Sort(comparer);
}
public void Sort(Comparison<TItem> comparison) {
var newComparer = new Comparer2<TItem>((x, y) => comparison(x, y));
Sort(newComparer);
}
public void Sort(IComparer<TItem> comparer) {
List<TItem> list = base.Items as List<TItem>;
if (list != null) {
list.Sort(comparer);
}
}
}
public class Comparer2<T> : Comparer<T> {
//private readonly Func<T, T, int> _compareFunction;
private readonly Comparison<T> _compareFunction;
#region Constructors
public Comparer2(Comparison<T> comparison) {
if (comparison == null) throw new ArgumentNullException("comparison");
_compareFunction = comparison;
}
#endregion
public override int Compare(T arg1, T arg2) {
return _compareFunction(arg1, arg2);
}
}
public class DictionaryEnumerator<TKey, TValue> : IDictionaryEnumerator, IDisposable {
readonly IEnumerator<KeyValuePair<TKey, TValue>> impl;
public void Dispose() { impl.Dispose(); }
public DictionaryEnumerator(IDictionary<TKey, TValue> value) {
this.impl = value.GetEnumerator();
}
public void Reset() { impl.Reset(); }
public bool MoveNext() { return impl.MoveNext(); }
public DictionaryEntry Entry {
get {
var pair = impl.Current;
return new DictionaryEntry(pair.Key, pair.Value);
}
}
public object Key { get { return impl.Current.Key; } }
public object Value { get { return impl.Current.Value; } }
public object Current { get { return Entry; } }
}
}
如果没有一些测试，没有任何实现是完整的（但不幸的是，SO不会让我在一个帖子中发布那么多代码），所以我将不得不让你写测试。但是，我留下了一些，以便您可以了解它是如何工作的：
// http://unlicense.org
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using mattmc3.Common.Collections.Generic;
namespace mattmc3.Tests.Common.Collections.Generic {
[TestClass]
public class OrderedDictionaryTests {
private OrderedDictionary<string, string> GetAlphabetDictionary(IEqualityComparer<string> comparer = null) {
OrderedDictionary<string, string> alphabet = (comparer == null ? new OrderedDictionary<string, string>() : new OrderedDictionary<string, string>(comparer));
for (var a = Convert.ToInt32('a'); a <= Convert.ToInt32('z'); a++) {
var c = Convert.ToChar(a);
alphabet.Add(c.ToString(), c.ToString().ToUpper());
}
Assert.AreEqual(26, alphabet.Count);
return alphabet;
}
private List<KeyValuePair<string, string>> GetAlphabetList() {
var alphabet = new List<KeyValuePair<string, string>>();
for (var a = Convert.ToInt32('a'); a <= Convert.ToInt32('z'); a++) {
var c = Convert.ToChar(a);
alphabet.Add(new KeyValuePair<string, string>(c.ToString(), c.ToString().ToUpper()));
}
Assert.AreEqual(26, alphabet.Count);
return alphabet;
}
[TestMethod]
public void TestAdd() {
var od = new OrderedDictionary<string, string>();
Assert.AreEqual(0, od.Count);
Assert.AreEqual(-1, od.IndexOf("foo"));
od.Add("foo", "bar");
Assert.AreEqual(1, od.Count);
Assert.AreEqual(0, od.IndexOf("foo"));
Assert.AreEqual(od[0], "bar");
Assert.AreEqual(od["foo"], "bar");
Assert.AreEqual(od.GetItem(0).Key, "foo");
Assert.AreEqual(od.GetItem(0).Value, "bar");
}
[TestMethod]
public void TestRemove() {
var od = new OrderedDictionary<string, string>();
od.Add("foo", "bar");
Assert.AreEqual(1, od.Count);
od.Remove("foo");
Assert.AreEqual(0, od.Count);
}
[TestMethod]
public void TestRemoveAt() {
var od = new OrderedDictionary<string, string>();
od.Add("foo", "bar");
Assert.AreEqual(1, od.Count);
od.RemoveAt(0);
Assert.AreEqual(0, od.Count);
}
[TestMethod]
public void TestClear() {
var od = GetAlphabetDictionary();
Assert.AreEqual(26, od.Count);
od.Clear();
Assert.AreEqual(0, od.Count);
}
[TestMethod]
public void TestOrderIsPreserved() {
var alphabetDict = GetAlphabetDictionary();
var alphabetList = GetAlphabetList();
Assert.AreEqual(26, alphabetDict.Count);
Assert.AreEqual(26, alphabetList.Count);
var keys = alphabetDict.Keys.ToList();
var values = alphabetDict.Values.ToList();
for (var i = 0; i < 26; i++) {
var dictItem = alphabetDict.GetItem(i);
var listItem = alphabetList[i];
var key = keys[i];
var value = values[i];
Assert.AreEqual(dictItem, listItem);
Assert.AreEqual(key, listItem.Key);
Assert.AreEqual(value, listItem.Value);
}
}
[TestMethod]
public void TestTryGetValue() {
var alphabetDict = GetAlphabetDictionary();
string result = null;
Assert.IsFalse(alphabetDict.TryGetValue("abc", out result));
Assert.IsNull(result);
Assert.IsTrue(alphabetDict.TryGetValue("z", out result));
Assert.AreEqual("Z", result);
}
[TestMethod]
public void TestEnumerator() {
var alphabetDict = GetAlphabetDictionary();
var keys = alphabetDict.Keys.ToList();
Assert.AreEqual(26, keys.Count);
var i = 0;
foreach (var kvp in alphabetDict) {
var value = alphabetDict[kvp.Key];
Assert.AreEqual(kvp.Value, value);
i++;
}
}
[TestMethod]
public void TestInvalidIndex() {
var alphabetDict = GetAlphabetDictionary();
try {
var notGonnaWork = alphabetDict[100];
Assert.IsTrue(false, "Exception should have thrown");
}
catch (Exception ex) {
Assert.IsTrue(ex.Message.Contains("index is outside the bounds"));
}
}
[TestMethod]
public void TestMissingKey() {
var alphabetDict = GetAlphabetDictionary();
try {
var notGonnaWork = alphabetDict["abc"];
Assert.IsTrue(false, "Exception should have thrown");
}
catch (Exception ex) {
Assert.IsTrue(ex.Message.Contains("key is not present"));
}
}
[TestMethod]
public void TestUpdateExistingValue() {
var alphabetDict = GetAlphabetDictionary();
Assert.IsTrue(alphabetDict.ContainsKey("c"));
Assert.AreEqual(2, alphabetDict.IndexOf("c"));
Assert.AreEqual(alphabetDict[2], "C");
alphabetDict[2] = "CCC";
Assert.IsTrue(alphabetDict.ContainsKey("c"));
Assert.AreEqual(2, alphabetDict.IndexOf("c"));
Assert.AreEqual(alphabetDict[2], "CCC");
}
[TestMethod]
public void TestInsertValue() {
var alphabetDict = GetAlphabetDictionary();
Assert.IsTrue(alphabetDict.ContainsKey("c"));
Assert.AreEqual(2, alphabetDict.IndexOf("c"));
Assert.AreEqual(alphabetDict[2], "C");
Assert.AreEqual(26, alphabetDict.Count);
Assert.IsFalse(alphabetDict.ContainsValue("ABC"));
alphabetDict.Insert(2, "abc", "ABC");
Assert.IsTrue(alphabetDict.ContainsKey("c"));
Assert.AreEqual(2, alphabetDict.IndexOf("abc"));
Assert.AreEqual(alphabetDict[2], "ABC");
Assert.AreEqual(27, alphabetDict.Count);
Assert.IsTrue(alphabetDict.ContainsValue("ABC"));
}
[TestMethod]
public void TestValueComparer() {
var alphabetDict = GetAlphabetDictionary();
Assert.IsFalse(alphabetDict.ContainsValue("a"));
Assert.IsTrue(alphabetDict.ContainsValue("a", StringComparer.OrdinalIgnoreCase));
}
[TestMethod]
public void TestSortByKeys() {
var alphabetDict = GetAlphabetDictionary();
var reverseAlphabetDict = GetAlphabetDictionary();
Comparison<string> stringReverse = ((x, y) => (String.Equals(x, y) ? 0 : String.Compare(x, y) >= 1 ? -1 : 1));
reverseAlphabetDict.SortKeys(stringReverse);
for (int j = 0, k = 25; j < alphabetDict.Count; j++, k--) {
var ascValue = alphabetDict.GetItem(j);
var dscValue = reverseAlphabetDict.GetItem(k);
Assert.AreEqual(ascValue.Key, dscValue.Key);
Assert.AreEqual(ascValue.Value, dscValue.Value);
}
}
- 更新 -
此处以及其他非常有用的缺少核心.NET库的来源：https://github.com/mattmc3/dotmore/blob/master/dotmore/Collections/Generic/OrderedDictionary.cs
答案 1 :(得分：57)
（就我所知，.NET 4也是如此。）
但你可以vote for it at Visual Studio's UserVoice（2016-10-04）！
答案 2 :(得分：31)
对于记录，有一个通用KeyedCollection，允许通过int和key索引对象。密钥必须嵌入到值中。
答案 3 :(得分：18)
这是一个奇怪的发现：System.Web.Extensions.dll中的System.Web.Util命名空间包含一个通用的OrderedDictionary
// Type: System.Web.Util.OrderedDictionary`2
// Assembly: System.Web.Extensions, Version=4.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35
// Assembly location: C:\Windows\Microsoft.NET\Framework\v4.0.30319\System.Web.Extensions.dll
namespace System.Web.Util
{
internal class OrderedDictionary<TKey, TValue> : IDictionary<TKey, TValue>, ICollection<KeyValuePair<TKey, TValue>>, IEnumerable<KeyValuePair<TKey, TValue>>, IEnumerable
不确定为什么MS把它放在那里而不是System.Collections.Generic包，但我认为你可以简单地复制粘贴代码并使用它（它是内部的，所以不能直接使用它）。看起来该实现使用标准字典和单独的键/值列表。很简单...
答案 4 :(得分：17)
对于它的价值，这是我如何解决它：
public class PairList<TKey, TValue> : List<KeyValuePair<TKey, TValue>> {
Dictionary<TKey, int> itsIndex = new Dictionary<TKey, int>();
public void Add(TKey key, TValue value) {
Add(new KeyValuePair<TKey, TValue>(key, value));
itsIndex.Add(key, Count-1);
}
public TValue Get(TKey key) {
var idx = itsIndex[key];
return this[idx].Value;
}
}
可以像这样初始化：
var pairList = new PairList<string, string>
{
{ "pitcher", "Ken" },
{ "catcher", "Brad"},
{ "left fielder", "Stan"},
};
并像这样访问：
foreach (var pair in pairList)
{
Console.WriteLine("position: {0}, player: {1}",
pair.Key, pair.Value);
}
// Guaranteed to print in the order of initialization
答案 5 :(得分：14)
OrderedDictionary的通用版本的一个主要概念问题是，OrderedDictionary<TKey,TValue>的用户希望能够使用int以数字方式对其进行索引，或者使用查找进行查找一个TKey。当唯一类型的键是Object时，与非泛型OrderedDictionary的情况一样，传递给索引器的参数类型足以区分是应该执行什么类型的索引操作。但实际上，不清楚OrderedDictionary<int, TValue>的索引器应该如何表现。
如果像Drawing.Point这样的类推荐并遵循一条规则，即分段可变结构应该将其可变元素作为字段而不是属性公开，并且不使用修改this的属性设置器，那么{ {1}}可以有效地公开返回OrderedDictionary<TKey,TValue>结构的ByIndex属性，该结构包含对字典的引用，并且具有索引属性，其getter和setter将调用Indexer和{{在它上面。因此，可以说GetByIndex之类的东西可以将3添加到字典的第六个元素中。
不幸的是，为了使编译器接受这样的事情，有必要让SetByIndex属性在每次调用时都返回一个新的类实例而不是结构，从而消除了通过避免装箱获得的优势
在VB.NET中，可以通过使用命名的索引属性解决该问题（因此MyDict.ByIndex[5] += 3;将是ByIndex的成员，而不是要求MyDict.ByIndex[int]成为成员包含索引器的MyDict，但C＃不允许这样的事情。
提供MyDict.ByIndex可能仍然值得，但是首先提供泛型的大部分原因是允许它们使用值类型。
答案 6 :(得分：6)
出于很多目的，我发现人们可以使用List<KeyValuePair<K, V>>。 （显然，如果你需要扩展Dictionary，那就不是了，如果你需要比O（n）键值查找更好的话，那就不行了。）
答案 7 :(得分：5)
是的，这是一个不幸的遗漏。我想念Python的OrderedDict
记住首次插入密钥的顺序的字典。如果新条目覆盖现有条目，则原始插入位置保持不变。删除一个条目并重新插入它将把它移到最后。
所以我在C＃中编写了自己的OrderedDictionary<K,V>类。它是如何工作的？它维护着两个集合 - 一个vanilla无序字典和一个有序的键列表。使用此解决方案，标准字典操作保持其快速复杂性，并且索引查找也很快。
https://gist.github.com/hickford/5137384
这是界面
/// <summary>
/// A dictionary that remembers the order that keys were first inserted. If a new entry overwrites an existing entry, the original insertion position is left unchanged. Deleting an entry and reinserting it will move it to the end.
/// </summary>
/// <typeparam name="TKey">The type of keys</typeparam>
/// <typeparam name="TValue">The type of values</typeparam>
public interface IOrderedDictionary<TKey, TValue> : IDictionary<TKey, TValue>
{
/// <summary>
/// The value of the element at the given index.
/// </summary>
TValue this[int index] { get; set; }
/// <summary>
/// Find the position of an element by key. Returns -1 if the dictionary does not contain an element with the given key.
/// </summary>
int IndexOf(TKey key);
/// <summary>
/// Insert an element at the given index.
/// </summary>
void Insert(int index, TKey key, TValue value);
/// <summary>
/// Remove the element at the given index.
/// </summary>
void RemoveAt(int index);
}
答案 8 :(得分：5)
有SortedDictionary<TKey, TValue>。虽然语义上很接近，但我并没有声称它与OrderedDictionary相同，只是因为它们不是。甚至从性能特征。然而，Dictionary<TKey, TValue>（以及那个范围OrderedDictionary和答案中提供的实现）和SortedDictionary之间非常有趣且非常重要的区别是后者在下面使用二叉树。这是至关重要的区别，因为它使类不受应用于泛型类的内存约束的影响。当泛型类用于处理大量键值对时，请参阅此线程关于OutOfMemoryExceptions抛出的内容。
答案 9 :(得分：3)
作为@ V.B评论的后续行动。这是System.Runtime.Collections.OrderedDictionary<,>的可访问实现。我本来打算通过反射来访问它并通过工厂提供它，但是这里的dll似乎根本不是很容易访问，所以我只是自己拉动了源代码。
有一点需要注意的是，这里的索引器不会抛出 KeyNotFoundException。我绝对讨厌那个惯例，这是我在这个实现中所采取的自由。如果这对您很重要，只需替换return default(TValue);行即可。使用C＃6（compatible with Visual Studio 2013）
/// <summary>
/// System.Collections.Specialized.OrderedDictionary is NOT generic.
/// This class is essentially a generic wrapper for OrderedDictionary.
/// </summary>
/// <remarks>
/// Indexer here will NOT throw KeyNotFoundException
/// </remarks>
public class OrderedDictionary<TKey, TValue> : IDictionary<TKey, TValue>, IDictionary
{
private readonly OrderedDictionary _privateDictionary;
public OrderedDictionary()
{
_privateDictionary = new OrderedDictionary();
}
public OrderedDictionary(IDictionary<TKey, TValue> dictionary)
{
if (dictionary == null) return;
_privateDictionary = new OrderedDictionary();
foreach (var pair in dictionary)
{
_privateDictionary.Add(pair.Key, pair.Value);
}
}
public bool IsReadOnly => false;
public int Count => _privateDictionary.Count;
int ICollection.Count => _privateDictionary.Count;
object ICollection.SyncRoot => ((ICollection)_privateDictionary).SyncRoot;
bool ICollection.IsSynchronized => ((ICollection)_privateDictionary).IsSynchronized;
bool IDictionary.IsFixedSize => ((IDictionary)_privateDictionary).IsFixedSize;
bool IDictionary.IsReadOnly => _privateDictionary.IsReadOnly;
ICollection IDictionary.Keys => _privateDictionary.Keys;
ICollection IDictionary.Values => _privateDictionary.Values;
void IDictionary.Add(object key, object value)
{
_privateDictionary.Add(key, value);
}
void IDictionary.Clear()
{
_privateDictionary.Clear();
}
bool IDictionary.Contains(object key)
{
return _privateDictionary.Contains(key);
}
IDictionaryEnumerator IDictionary.GetEnumerator()
{
return _privateDictionary.GetEnumerator();
}
void IDictionary.Remove(object key)
{
_privateDictionary.Remove(key);
}
object IDictionary.this[object key]
{
get { return _privateDictionary[key]; }
set { _privateDictionary[key] = value; }
}
void ICollection.CopyTo(Array array, int index)
{
_privateDictionary.CopyTo(array, index);
}
public TValue this[TKey key]
{
get
{
if (key == null) throw new ArgumentNullException(nameof(key));
if (_privateDictionary.Contains(key))
{
return (TValue) _privateDictionary[key];
}
return default(TValue);
}
set
{
if (key == null) throw new ArgumentNullException(nameof(key));
_privateDictionary[key] = value;
}
}
public ICollection<TKey> Keys
{
get
{
var keys = new List<TKey>(_privateDictionary.Count);
keys.AddRange(_privateDictionary.Keys.Cast<TKey>());
return keys.AsReadOnly();
}
}
public ICollection<TValue> Values
{
get
{
var values = new List<TValue>(_privateDictionary.Count);
values.AddRange(_privateDictionary.Values.Cast<TValue>());
return values.AsReadOnly();
}
}
public void Add(KeyValuePair<TKey, TValue> item)
{
Add(item.Key, item.Value);
}
public void Add(TKey key, TValue value)
{
if (key == null) throw new ArgumentNullException(nameof(key));
_privateDictionary.Add(key, value);
}
public void Clear()
{
_privateDictionary.Clear();
}
public bool Contains(KeyValuePair<TKey, TValue> item)
{
if (item.Key == null || !_privateDictionary.Contains(item.Key))
{
return false;
}
return _privateDictionary[item.Key].Equals(item.Value);
}
public bool ContainsKey(TKey key)
{
if (key == null) throw new ArgumentNullException(nameof(key));
return _privateDictionary.Contains(key);
}
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
if (array == null) throw new ArgumentNullException(nameof(array));
if (arrayIndex < 0) throw new ArgumentOutOfRangeException(nameof(arrayIndex));
if (array.Rank > 1 || arrayIndex >= array.Length
|| array.Length - arrayIndex < _privateDictionary.Count)
throw new ArgumentException("Bad Copy ToArray", nameof(array));
var index = arrayIndex;
foreach (DictionaryEntry entry in _privateDictionary)
{
array[index] =
new KeyValuePair<TKey, TValue>((TKey) entry.Key, (TValue) entry.Value);
index++;
}
}
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
foreach (DictionaryEntry entry in _privateDictionary)
{
yield return
new KeyValuePair<TKey, TValue>((TKey) entry.Key, (TValue) entry.Value);
}
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
public bool Remove(KeyValuePair<TKey, TValue> item)
{
if (false == Contains(item)) return false;
_privateDictionary.Remove(item.Key);
return true;
}
public bool Remove(TKey key)
{
if (key == null) throw new ArgumentNullException(nameof(key));
if (false == _privateDictionary.Contains(key)) return false;
_privateDictionary.Remove(key);
return true;
}
public bool TryGetValue(TKey key, out TValue value)
{
if (key == null) throw new ArgumentNullException(nameof(key));
var keyExists = _privateDictionary.Contains(key);
value = keyExists ? (TValue) _privateDictionary[key] : default(TValue);
return keyExists;
}
}
答案 10 :(得分：2)
对于在NuGet中寻找“官方”软件包选项的用户，.NET CoreFX Lab已接受通用OrderedDictionary的实现。如果一切顺利，该类型最终将被批准并集成到主要的.NET CoreFX存储库中。
此实施有可能会被拒绝。
可以在此处找到确切具有此类型可用的NuGet程序包 https://www.nuget.org/packages/Microsoft.Experimental.Collections/1.0.6-e190117-3
或者您可以在Visual Studio中安装该软件包。浏览软件包“ Microsoft.Experimental.Collections”，并确保选中“包括预发行版”复选框。
如果该类型正式可用，将更新此帖子。
答案 11 :(得分：1)
我通过围绕OrderedDictionary<TKey, TValue>并添加私人SortedList<TKey, TValue> Dictionary<TKey, int>来实施通用_order。然后我创建了Comparer<TKey>的内部实现，传递了对_order字典的引用。然后我将此比较器用于内部SortedList。此类保持传递给构造函数的元素的顺序和添加顺序。
此实现具有与SortedList<TKey, TValue>几乎相同的大O特性，因为添加和删除_order是O（1）。每个元素都将采用（根据书中的'C＃4 in a Nutshell'，p.292，表7-1）22个额外的内存空间（开销）+ 4（整数顺序）+ TKey大小（假设8）= 34与SortedList<TKey, TValue>两个字节的开销一起，总开销为36个字节，而同一本书则表示非泛型OrderedDictionary的开销为59个字节。
如果我将sorted=true传递给构造函数，则根本不使用_order，OrderedDictionary<TKey, TValue>正好是SortedList<TKey, TValue>，包装的开销很小，如果有意义的话。
我要在OrderedDictionary<TKey, TValue>中存储不那么多的大型参考对象，所以对我来说这个ca.可以容忍36字节的开销。
主要代码如下。完整更新的代码位于此gist。
public class OrderedList<TKey, TValue> : IDictionary<TKey, TValue>, IDictionary
{
private readonly Dictionary<TKey, int> _order;
private readonly SortedList<TKey, TValue> _internalList;
private readonly bool _sorted;
private readonly OrderComparer _comparer;
public OrderedList(IDictionary<TKey, TValue> dictionary, bool sorted = false)
{
_sorted = sorted;
if (dictionary == null)
dictionary = new Dictionary<TKey, TValue>();
if (_sorted)
{
_internalList = new SortedList<TKey, TValue>(dictionary);
}
else
{
_order = new Dictionary<TKey, int>();
_comparer = new OrderComparer(ref _order);
_internalList = new SortedList<TKey, TValue>(_comparer);
// Keep order of the IDictionary
foreach (var kvp in dictionary)
{
Add(kvp);
}
}
}
public OrderedList(bool sorted = false)
: this(null, sorted)
{
}
private class OrderComparer : Comparer<TKey>
{
public Dictionary<TKey, int> Order { get; set; }
public OrderComparer(ref Dictionary<TKey, int> order)
{
Order = order;
}
public override int Compare(TKey x, TKey y)
{
var xo = Order[x];
var yo = Order[y];
return xo.CompareTo(yo);
}
}
private void ReOrder()
{
var i = 0;
_order = _order.OrderBy(kvp => kvp.Value).ToDictionary(kvp => kvp.Key, kvp => i++);
_comparer.Order = _order;
_lastOrder = _order.Values.Max() + 1;
}
public void Add(TKey key, TValue value)
{
if (!_sorted)
{
_order.Add(key, _lastOrder);
_lastOrder++;
// Very rare event
if (_lastOrder == int.MaxValue)
ReOrder();
}
_internalList.Add(key, value);
}
public bool Remove(TKey key)
{
var result = _internalList.Remove(key);
if (!_sorted)
_order.Remove(key);
return result;
}
// Other IDictionary<> + IDictionary members implementation wrapping around _internalList
// ...
}
答案 12 :(得分：0)
这不是OrderedDictionary<,>的另一个版本/解决方案，但我做了一个实验，测试了答案中提到的4个版本：@Colonel Panic，@ mattmc3，@ V.B。 @克里斯·马里西克（Chris Marisic）。这是作为反馈。好吧，部分原因是因为我不得不承认我没有剖析代码，因此功能或安全检查可能有所不同。但我仍然认为，反馈对于他们的表现将是有用的。如您所见，时间可能从几毫秒到一刻钟。
然后，我用O（n）搜索写了一个包含2个键和值类对象列表的朴素的最小版本，以了解O（1）访问带来的好处。
Testbed是带有Unity 3D的Microsoft Visual Studio Community 2019，每个测试连续4次，我想在其中复制真实场景的代码是
using System.Text;
using UnityEngine;
public class TessyOne : MonoBehaviour
{
public const int iterations = 50000;
private System.Diagnostics.Stopwatch stopwatch;
private System.Random random;
public float stopwatchDuration;
public class Ala
{
public int inta;
public float fla;
public string stra;
public Ben bena;
public Ala(int i, float f, string s, Ben b)
{
inta = i; fla = f; stra = s; bena = b;
}
}
public class Ben
{
public int inte;
public float fle;
public string stre;
public Ben(int i, float f, string s)
{
inte = i; fle = f; stre = s;
}
}
//public Naive.OrderedDictionary<Ala, Ben> alasToBens = new Naive.OrderedDictionary<Ala, Ben>();
//public Hickford.OrderedDictionary<Ala, Ben> alasToBens = new Hickford.OrderedDictionary<Ala, Ben>();
//public Mattmc3.OrderedDictionary<Ala, Ben> alasToBens = new Mattmc3.OrderedDictionary<Ala, Ben>();
public Marisic.OrderedDictionary<Ala, Ben> alasToBens = new Marisic.OrderedDictionary<Ala, Ben>();
//public VB.OrderedList<Ala, Ben> alasToBens = new VB.OrderedList<Ala, Ben>(null, false);
Ala[] alarray = new Ala[iterations];
Ben[] berray = new Ben[iterations];
// This is the entry point of the application
private void Start()
{
stopwatch = new System.Diagnostics.Stopwatch();
random = new System.Random(2020);
for(int i = 0; i < iterations; ++i)
{
berray[i] = new Ben(random.Next(),
(float)random.NextDouble(),
MakeRandomString((ushort)random.Next(1, 10)));
alarray[i] = new Ala(random.Next(),
(float)random.NextDouble(),
MakeRandomString((ushort)random.Next(1, 10)),
berray[i]);
// uncomment for testing ContainsKey() and Remove(), comment for Add()
alasToBens.Add(alarray[i], berray[i]);
}
stopwatch.Start();
for(int i = iterations - 1; i > -1; --i)
{
//alasToBens.Add(alarray[i], berray[i]);
//alasToBens.ContainsKey(alarray[i]);
alasToBens.Remove(alarray[i]);
}
stopwatch.Stop();
stopwatchDuration = stopwatch.ElapsedMilliseconds;
}
public string MakeRandomString(ushort length)
{
StringBuilder sb = new StringBuilder();
for(ushort u = 0; u < length; ++u)
{
sb.Append((char)Random.Range(33, 126)); // regular ASCII chars
}
return sb.ToString();
}
}
请注意，这些测试至少是针对天真的版本的最坏情况，因为它会从索引0到iterations遍历整个集合，并从头到尾进行搜索。对于50000个条目的字典，我以毫秒为单位测量了Add()，ContainsKey()和Remove()。
结果：
+----------+----------------+----------------+--------------------------------+
| ms | Add() | ContainsKey() | Remove() |
+----------+----------------+----------------+--------------------------------+
| Hickford | 7, 8, 7, 8 | 2, 2, 3, 2 | 7400, 7503, 7419, 7421 |
| Mattmc3 | 23, 24, 24, 23 | 3, 3, 3, 3 | 890404, 913465, 875387, 877792 |
| Marisic | 27, 28, 28, 27 | 4, 4, 4, 4 | 27401, 27627, 27341, 27349 |
| V.B. | 76, 76, 75, 75 | 59, 60, 60, 60 | 66, 67, 67, 67 |
| | | | |
| Naive | 19651, 19761 | 25335, 25416 | 25259, 25306 |
+----------+----------------+----------------+--------------------------------+