我需要一个线程安全的集合来保存没有重复的项目。ConcurrentBag<T>允许非唯一项目并且HashSet<T>不是线程安全的。.NET Framework 4.5 中有这样的集合吗？
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19
这是我刚刚编写的用于执行此 ConcurrentSet 构造的一些代码：
public class ConcurrentSet<T> : IEnumerable<T>, ISet<T>, ICollection<T>
{
private readonly ConcurrentDictionary<T, byte> _dictionary = new ConcurrentDictionary<T, byte>();
/// <summary>
/// Returns an enumerator that iterates through the collection.
/// </summary>
/// <returns>
/// A <see cref="T:System.Collections.Generic.IEnumerator`1"/> that can be used to iterate through the collection.
/// </returns>
public IEnumerator<T> GetEnumerator()
{
return _dictionary.Keys.GetEnumerator();
}
/// <summary>
/// Returns an enumerator that iterates through a collection.
/// </summary>
/// <returns>
/// An <see cref="T:System.Collections.IEnumerator"/> object that can be used to iterate through the collection.
/// </returns>
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
/// <summary>
/// Removes the first occurrence of a specific object from the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <returns>
/// true if <paramref name="item"/> was successfully removed from the <see cref="T:System.Collections.Generic.ICollection`1"/>; otherwise, false. This method also returns false if <paramref name="item"/> is not found in the original <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </returns>
/// <param name="item">The object to remove from the <see cref="T:System.Collections.Generic.ICollection`1"/>.</param><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only.</exception>
public bool Remove(T item)
{
return TryRemove(item);
}
/// <summary>
/// Gets the number of elements in the set.
/// </summary>
public int Count
{
get { return _dictionary.Count; }
}
/// <summary>
/// Gets a value indicating whether the <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only.
/// </summary>
/// <returns>
/// true if the <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only; otherwise, false.
/// </returns>
public bool IsReadOnly { get { return false; } }
/// <summary>
/// Gets a value that indicates if the set is empty.
/// </summary>
public bool IsEmpty
{
get { return _dictionary.IsEmpty; }
}
public ICollection<T> Values
{
get { return _dictionary.Keys; }
}
/// <summary>
/// Adds an item to the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <param name="item">The object to add to the <see cref="T:System.Collections.Generic.ICollection`1"/>.</param><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only.</exception>
void ICollection<T>.Add(T item)
{
if(!Add(item))
throw new ArgumentException("Item already exists in set.");
}
/// <summary>
/// Modifies the current set so that it contains all elements that are present in both the current set and in the specified collection.
/// </summary>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public void UnionWith(IEnumerable<T> other)
{
foreach (var item in other)
TryAdd(item);
}
/// <summary>
/// Modifies the current set so that it contains only elements that are also in a specified collection.
/// </summary>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public void IntersectWith(IEnumerable<T> other)
{
var enumerable = other as IList<T> ?? other.ToArray();
foreach (var item in this)
{
if (!enumerable.Contains(item))
TryRemove(item);
}
}
/// <summary>
/// Removes all elements in the specified collection from the current set.
/// </summary>
/// <param name="other">The collection of items to remove from the set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public void ExceptWith(IEnumerable<T> other)
{
foreach (var item in other)
TryRemove(item);
}
/// <summary>
/// Modifies the current set so that it contains only elements that are present either in the current set or in the specified collection, but not both.
/// </summary>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public void SymmetricExceptWith(IEnumerable<T> other)
{
throw new NotImplementedException();
}
/// <summary>
/// Determines whether a set is a subset of a specified collection.
/// </summary>
/// <returns>
/// true if the current set is a subset of <paramref name="other"/>; otherwise, false.
/// </returns>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public bool IsSubsetOf(IEnumerable<T> other)
{
var enumerable = other as IList<T> ?? other.ToArray();
return this.AsParallel().All(enumerable.Contains);
}
/// <summary>
/// Determines whether the current set is a superset of a specified collection.
/// </summary>
/// <returns>
/// true if the current set is a superset of <paramref name="other"/>; otherwise, false.
/// </returns>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public bool IsSupersetOf(IEnumerable<T> other)
{
return other.AsParallel().All(Contains);
}
/// <summary>
/// Determines whether the current set is a correct superset of a specified collection.
/// </summary>
/// <returns>
/// true if the <see cref="T:System.Collections.Generic.ISet`1"/> object is a correct superset of <paramref name="other"/>; otherwise, false.
/// </returns>
/// <param name="other">The collection to compare to the current set. </param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public bool IsProperSupersetOf(IEnumerable<T> other)
{
var enumerable = other as IList<T> ?? other.ToArray();
return this.Count != enumerable.Count && IsSupersetOf(enumerable);
}
/// <summary>
/// Determines whether the current set is a property (strict) subset of a specified collection.
/// </summary>
/// <returns>
/// true if the current set is a correct subset of <paramref name="other"/>; otherwise, false.
/// </returns>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public bool IsProperSubsetOf(IEnumerable<T> other)
{
var enumerable = other as IList<T> ?? other.ToArray();
return Count != enumerable.Count && IsSubsetOf(enumerable);
}
/// <summary>
/// Determines whether the current set overlaps with the specified collection.
/// </summary>
/// <returns>
/// true if the current set and <paramref name="other"/> share at least one common element; otherwise, false.
/// </returns>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public bool Overlaps(IEnumerable<T> other)
{
return other.AsParallel().Any(Contains);
}
/// <summary>
/// Determines whether the current set and the specified collection contain the same elements.
/// </summary>
/// <returns>
/// true if the current set is equal to <paramref name="other"/>; otherwise, false.
/// </returns>
/// <param name="other">The collection to compare to the current set.</param><exception cref="T:System.ArgumentNullException"><paramref name="other"/> is null.</exception>
public bool SetEquals(IEnumerable<T> other)
{
var enumerable = other as IList<T> ?? other.ToArray();
return Count == enumerable.Count && enumerable.AsParallel().All(Contains);
}
/// <summary>
/// Adds an element to the current set and returns a value to indicate if the element was successfully added.
/// </summary>
/// <returns>
/// true if the element is added to the set; false if the element is already in the set.
/// </returns>
/// <param name="item">The element to add to the set.</param>
public bool Add(T item)
{
return TryAdd(item);
}
public void Clear()
{
_dictionary.Clear();
}
public bool Contains(T item)
{
return _dictionary.ContainsKey(item);
}
/// <summary>
/// Copies the elements of the <see cref="T:System.Collections.Generic.ICollection`1"/> to an <see cref="T:System.Array"/>, starting at a particular <see cref="T:System.Array"/> index.
/// </summary>
/// <param name="array">The one-dimensional <see cref="T:System.Array"/> that is the destination of the elements copied from <see cref="T:System.Collections.Generic.ICollection`1"/>. The <see cref="T:System.Array"/> must have zero-based indexing.</param><param name="arrayIndex">The zero-based index in <paramref name="array"/> at which copying begins.</param><exception cref="T:System.ArgumentNullException"><paramref name="array"/> is null.</exception><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="arrayIndex"/> is less than 0.</exception><exception cref="T:System.ArgumentException"><paramref name="array"/> is multidimensional.-or-The number of elements in the source <see cref="T:System.Collections.Generic.ICollection`1"/> is greater than the available space from <paramref name="arrayIndex"/> to the end of the destination <paramref name="array"/>.-or-Type <paramref name="T"/> cannot be cast automatically to the type of the destination <paramref name="array"/>.</exception>
public void CopyTo(T[] array, int arrayIndex)
{
Values.CopyTo(array, arrayIndex);
}
public T[] ToArray()
{
return _dictionary.Keys.ToArray();
}
public bool TryAdd(T item)
{
return _dictionary.TryAdd(item, default(byte));
}
public bool TryRemove(T item)
{
byte donotcare;
return _dictionary.TryRemove(item, out donotcare);
}
}
于 2012-09-28T13:05:56.507 回答
17
我建议您使用 aConcurrentDictionary并且只为每个条目使用一个虚拟值。就效率而言（具有所有这些虚拟值）很烦人，但我怀疑在大多数应用程序中这将是微不足道的。
您可能希望将其包装在您自己的ConcurrentSet实现中，这足以满足您的目的，这样您就不需要在大部分代码中看到抽象漏洞。
于 2012-09-25T14:52:09.433 回答