構建可反轉排序的泛型字典 (8/9)：實現 IDictionary<TKey,TValue> 介面完整代碼

本節目標

在已實現非泛型 IDictionary、IEnumerable 基礎上，實現泛型 IDictionary<TKey,TValue> 介面，提供類型安全的鍵值操作、索引器、Keys/Values 強類型集合視圖。

類別宣告更新

public class ReversibleSortedList : 
    IDictionary,
    IDictionary,
    ICollection>,
    IEnumerable>,
    ICollection,
    IEnumerable
{
    // ... 現有欄位與方法
}

ICollection<KeyValuePair<TKey,TValue>> 顯式實現

bool ICollection>.IsReadOnly => false;

void ICollection>.Add(KeyValuePair item)
    => Add(item.Key, item.Value);

bool ICollection>.Contains(KeyValuePair item)
{
    int idx = IndexOfKey(item.Key);
    return idx >= 0 && EqualityComparer.Default.Equals(_values[idx], item.Value);
}

void ICollection>.CopyTo(KeyValuePair[] array, int arrayIndex)
{
    if (array == null) throw new ArgumentNullException(nameof(array));
    if (arrayIndex < 0 || arrayIndex > array.Length) throw new ArgumentOutOfRangeException(nameof(arrayIndex));
    if (array.Length - arrayIndex < Count) throw new ArgumentException("目標陣列空間不足");

    for (int i = 0; i < Count; i++)
        array[arrayIndex + i] = new KeyValuePair(_keys[i], _values[i]);
}

bool ICollection>.Remove(KeyValuePair item)
{
    int idx = IndexOfKey(item.Key);
    if (idx >= 0 && EqualityComparer.Default.Equals(_values[idx], item.Value))
    {
        RemoveAt(idx);
        return true;
    }
    return false;
}

IDictionary<TKey,TValue> 核心成員（公有實現）

// 強類型 Keys/Values 集合視圖
public IList Keys => GetKeyListHelper();
public IList Values => GetValueListHelper();

// 索引器：Get 或 Add/Update
public TValue this[TKey key]
{
    get
    {
        int idx = IndexOfKey(key);
        return idx >= 0 ? _values[idx] : default(TValue);
    }
    set
    {
        if (key == null) throw new ArgumentNullException(nameof(key));
        int idx = Array.BinarySearch(_keys, 0, _size, key, _comparer);
        if (idx >= 0)
        {
            _values[idx] = value;
            _version++;
        }
        else
        {
            Insert(~idx, key, value); // ~idx = 插入位置
        }
    }
}

public bool Remove(TKey key)
{
    int idx = IndexOfKey(key);
    if (idx >= 0) { RemoveAt(idx); return true; }
    return false;
}

public bool TryGetValue(TKey key, out TValue value)
{
    int idx = IndexOfKey(key);
    if (idx >= 0) { value = _values[idx]; return true; }
    value = default(TValue);
    return false;
}

輔助方法：RemoveAt 與內部 Insert

public void RemoveAt(int index)
{
    if (index < 0 || index >= _size) throw new ArgumentOutOfRangeException(nameof(index));
    _size--;
    if (index < _size)
    {
        Array.Copy(_keys, index + 1, _keys, index, _size - index);
        Array.Copy(_values, index + 1, _values, index, _size - index);
    }
    _keys[_size] = default(TKey);
    _values[_size] = default(TValue);
    _version++;
}

// 內部插入（索引已驗證）
private void Insert(int index, TKey key, TValue value)
{
    if (_size == _keys.Length) EnsureCapacity(_size + 1);
    if (index < _size)
    {
        Array.Copy(_keys, index, _keys, index + 1, _size - index);
        Array.Copy(_values, index, _values, index + 1, _size - index);
    }
    _keys[index] = key;
    _values[index] = value;
    _size++; _version++;
}

測試驗證

static void Main()
{
    var rs = new ReversibleSortedList();
    rs.Add("3", "a"); rs.Add("1", "b"); rs.Add("2", "c");
    rs.Add("6", "d"); rs.Add("5", "e"); rs.Add("4", "f");

    Console.WriteLine("遍歷 (KeyValuePair):");
    foreach (var kv in rs) Console.WriteLine($"{kv.Key} {kv.Value}");

    Console.WriteLine("\n刪除鍵 \"2\" 和 \"5\":");
    rs.Remove("2"); rs.Remove("5");
    foreach (var kv in rs) Console.WriteLine($"{kv.Key} {kv.Value}");

    Console.WriteLine("\n索引器測試:");
    Console.WriteLine($"rs[\"3\"] = {rs["3"]}"); // a
    rs["3"] = "updated";
    Console.WriteLine($"rs[\"3\"] = {rs["3"]}"); // updated
    rs["9"] = "new"; // 新增
    Console.WriteLine($"rs[\"9\"] = {rs["9"]}"); // new

    Console.WriteLine($"\nTryGetValue(\"1\"): {rs.TryGetValue("1", out var v)}, v={v}");
    Console.WriteLine($"ContainsKey(\"6\"): {rs.ContainsKey("6")}");
}

輸出驗證所有操作符合預期，泛型介面實現完成。