KeysOrValuesCollectionAccessor.cs

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using System.Collections.Generic;
using System.Diagnostics;
 
namespace System.Collections.Immutable;
 
internal abstract class KeysOrValuesCollectionAccessor<TKey, TValue, T> : ICollection<T>, IEnumerable<T>, IEnumerable, ICollection where TKey : notnull
{
    private readonly IImmutableDictionary<TKey, TValue> _dictionary;
 
    private readonly IEnumerable<T> _keysOrValues;
 
    public bool IsReadOnly => true;
 
    public int Count => _dictionary.Count;
 
    protected IImmutableDictionary<TKey, TValue> Dictionary => _dictionary;
 
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    bool ICollection.IsSynchronized => true;
 
    [DebuggerBrowsable(DebuggerBrowsableState.Never)]
    object ICollection.SyncRoot => this;
 
    protected KeysOrValuesCollectionAccessor(IImmutableDictionary<TKey, TValue> dictionary, IEnumerable<T> keysOrValues)
    {
        Requires.NotNull(dictionary, "dictionary");
        Requires.NotNull(keysOrValues, "keysOrValues");
        _dictionary = dictionary;
        _keysOrValues = keysOrValues;
    }
 
    public void Add(T item)
    {
        throw new NotSupportedException();
    }
 
    public void Clear()
    {
        throw new NotSupportedException();
    }
 
    public abstract bool Contains(T item);
 
    public void CopyTo(T[] array, int arrayIndex)
    {
        Requires.NotNull(array, "array");
        Requires.Range(arrayIndex >= 0, "arrayIndex");
        Requires.Range(array.Length >= arrayIndex + Count, "arrayIndex");
        using IEnumerator<T> enumerator = GetEnumerator();
        while (enumerator.MoveNext())
        {
            T current = enumerator.Current;
            array[arrayIndex++] = current;
        }
    }
 
    public bool Remove(T item)
    {
        throw new NotSupportedException();
    }
 
    public IEnumerator<T> GetEnumerator()
    {
        return _keysOrValues.GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
 
    void ICollection.CopyTo(Array array, int arrayIndex)
    {
        Requires.NotNull(array, "array");
        Requires.Range(arrayIndex >= 0, "arrayIndex");
        Requires.Range(array.Length >= arrayIndex + Count, "arrayIndex");
        using IEnumerator<T> enumerator = GetEnumerator();
        while (enumerator.MoveNext())
        {
            T current = enumerator.Current;
            array.SetValue(current, arrayIndex++);
        }
    }
}