我需要知道如何在某个静态类中覆盖某个Dictionary的Add方法。有什么建议吗？
如果重要，字典看起来像这样：
public static Dictionary<MyEnum,MyArray[]>
有什么建议吗？
答案 0 :(得分：32)
您无法覆盖Add Dictionary<,>方法，因为它不是虚拟的。您可以通过在派生类中添加具有相同名称/签名的方法来隐藏它，但隐藏与覆盖不同。如果有人投射到基类，他仍然会调用错误的Add。
执行此操作的正确方法是创建自己的类，实现IDictionary<,>（接口），但 Dictionary<,>（类）而不是 一个Dictionary<,>。
class MyDictionary<TKey,TValue>:IDictionary<TKey,TValue>
{
private Dictionary<TKey,TValue> backingDictionary;
//Implement the interface here
//Delegating most of the logic to your backingDictionary
...
}
答案 1 :(得分：8)
我选择了CodesInChaos的解决方案。由于实现IDictionary<TKey, TValue>涉及一些开销，因此这是一个用于一般消费的虚拟实现。我在下面提供了一些评论和一个例子，供选读。如果我应该修理或改进某些东西，请告诉我。我没有做太多测试，但似乎可以覆盖add方法。
using System.Collections;
using System.Collections.Generic;
/// <summary>
/// Represents a collection of keys and values. This is an abstract base-class wrapping a <see cref="T:System.Collections.Generic.Dictionary`2"/> with
/// virtual method that can be overridden. This class can be used to override the default functionality of <see cref="T:System.Collections.Generic.Dictionary`2"/>.
/// </summary>
/// <typeparam name="TKey">The type of the keys in the dictionary.</typeparam>
/// <typeparam name="TValue">The type of the values in the dictionary.</typeparam>
public class VirtualDictionary<TKey, TValue> : IDictionary<TKey, TValue>
{
protected IDictionary<TKey, TValue> wrappedDictionary;
/// <summary>
/// Initializes a new instance of the <see cref="VirtualDictionary{TKey,TValue}"/> class that is empty, has the default initial capacity, and uses the default equality comparer for the key type.
/// </summary>
public VirtualDictionary()
{
wrappedDictionary = new Dictionary<TKey, TValue>();
}
/// <summary>
/// Initializes a new instance of the <see cref="VirtualDictionary{TKey,TValue}"/> class that is empty, has the specified initial capacity, and uses the default equality comparer for the key type.
/// </summary>
/// <param name="capacity">The initial number of elements that the <see cref="T:System.Collections.Generic.VirtualDictionary`2"/> can contain.</param><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="capacity"/> is less than 0.</exception>
public VirtualDictionary(int capacity)
{
wrappedDictionary = new Dictionary<TKey, TValue>(capacity);
}
/// <summary>
/// Initializes a new instance of the <see cref="VirtualDictionary{TKey,TValue}"/> class that is empty, has the default initial capacity, and uses the specified <see cref="T:System.Collections.Generic.IEqualityComparer`1"/>.
/// </summary>
/// <param name="comparer">The <see cref="T:System.Collections.Generic.IEqualityComparer`1"/> implementation to use when comparing keys, or null to use the default <see cref="T:System.Collections.Generic.EqualityComparer`1"/> for the type of the key.</param>
public VirtualDictionary(IEqualityComparer<TKey> comparer)
{
wrappedDictionary = new Dictionary<TKey, TValue>(comparer);
}
/// <summary>
/// Initializes a new instance of the <see cref="VirtualDictionary{TKey,TValue}"/> class that is empty, has the specified initial capacity, and uses the specified <see cref="T:System.Collections.Generic.IEqualityComparer`1"/>.
/// </summary>
/// <param name="capacity">The initial number of elements that the <see cref="VirtualDictionary{TKey,TValue}"/> can contain.</param><param name="comparer">The <see cref="T:System.Collections.Generic.IEqualityComparer`1"/> implementation to use when comparing keys, or null to use the default <see cref="T:System.Collections.Generic.EqualityComparer`1"/> for the type of the key.</param><exception cref="T:System.ArgumentOutOfRangeException"><paramref name="capacity"/> is less than 0.</exception>
public VirtualDictionary(int capacity, IEqualityComparer<TKey> comparer)
{
wrappedDictionary = new Dictionary<TKey, TValue>(capacity, comparer);
}
/// <summary>
/// Initializes a new instance of the <see cref="VirtualDictionary{TKey,TValue}"/> class that contains elements copied from the specified <see cref="T:System.Collections.Generic.IDictionary`2"/> and uses the default equality comparer for the key type.
/// </summary>
/// <param name="dictionary">The <see cref="T:System.Collections.Generic.IDictionary`2"/> whose elements are copied to the new <see cref="VirtualDictionary{TKey,TValue}"/>.</param><exception cref="T:System.ArgumentNullException"><paramref name="dictionary"/> is null.</exception><exception cref="T:System.ArgumentException"><paramref name="dictionary"/> contains one or more duplicate keys.</exception>
public VirtualDictionary(IDictionary<TKey, TValue> dictionary)
{
wrappedDictionary = new Dictionary<TKey, TValue>(dictionary);
}
/// <summary>
/// Initializes a new instance of the <see cref="VirtualDictionary{TKey,TValue}"/> class that contains elements copied from the specified <see cref="T:System.Collections.Generic.IDictionary`2"/> and uses the specified <see cref="T:System.Collections.Generic.IEqualityComparer`1"/>.
/// </summary>
/// <param name="dictionary">The <see cref="T:System.Collections.Generic.IDictionary`2"/> whose elements are copied to the new <see cref="VirtualDictionary{TKey,TValue}"/>.</param><param name="comparer">The <see cref="T:System.Collections.Generic.IEqualityComparer`1"/> implementation to use when comparing keys, or null to use the default <see cref="T:System.Collections.Generic.EqualityComparer`1"/> for the type of the key.</param><exception cref="T:System.ArgumentNullException"><paramref name="dictionary"/> is null.</exception><exception cref="T:System.ArgumentException"><paramref name="dictionary"/> contains one or more duplicate keys.</exception>
public VirtualDictionary(IDictionary<TKey, TValue> dictionary, IEqualityComparer<TKey> comparer)
{
wrappedDictionary = new Dictionary<TKey, TValue>(dictionary, comparer);
}
/// <summary>
/// Adds an element with the provided key and value to the <see cref="T:System.Collections.Generic.IDictionary`2"/>.
/// </summary>
/// <param name="key">The object to use as the key of the element to add.</param><param name="value">The object to use as the value of the element to add.</param><exception cref="T:System.ArgumentNullException"><paramref name="key"/> is null.</exception><exception cref="T:System.ArgumentException">An element with the same key already exists in the <see cref="T:System.Collections.Generic.IDictionary`2"/>.</exception><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.IDictionary`2"/> is read-only.</exception>
public virtual void Add(TKey key, TValue value)
{
wrappedDictionary.Add(key, value);
}
/// <summary>
/// Determines whether the <see cref="T:System.Collections.Generic.IDictionary`2"/> contains an element with the specified key.
/// </summary>
/// <returns>
/// true if the <see cref="T:System.Collections.Generic.IDictionary`2"/> contains an element with the key; otherwise, false.
/// </returns>
/// <param name="key">The key to locate in the <see cref="T:System.Collections.Generic.IDictionary`2"/>.</param><exception cref="T:System.ArgumentNullException"><paramref name="key"/> is null.</exception>
public virtual bool ContainsKey(TKey key)
{
return wrappedDictionary.ContainsKey(key);
}
/// <summary>
/// Gets an <see cref="T:System.Collections.Generic.ICollection`1"/> containing the keys of the <see cref="T:System.Collections.Generic.IDictionary`2"/>.
/// </summary>
/// <returns>
/// An <see cref="T:System.Collections.Generic.ICollection`1"/> containing the keys of the object that implements <see cref="T:System.Collections.Generic.IDictionary`2"/>.
/// </returns>
public virtual ICollection<TKey> Keys
{
get
{
return wrappedDictionary.Keys;
}
}
/// <summary>
/// Removes the element with the specified key from the <see cref="T:System.Collections.Generic.IDictionary`2"/>.
/// </summary>
/// <returns>
/// true if the element is successfully removed; otherwise, false. This method also returns false if <paramref name="key"/> was not found in the original <see cref="T:System.Collections.Generic.IDictionary`2"/>.
/// </returns>
/// <param name="key">The key of the element to remove.</param><exception cref="T:System.ArgumentNullException"><paramref name="key"/> is null.</exception><exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.IDictionary`2"/> is read-only.</exception>
public virtual bool Remove(TKey key)
{
return wrappedDictionary.Remove(key);
}
/// <summary>
/// Gets the value associated with the specified key.
/// </summary>
/// <returns>
/// true if the object that implements <see cref="T:System.Collections.Generic.IDictionary`2"/> contains an element with the specified key; otherwise, false.
/// </returns>
/// <param name="key">The key whose value to get.</param><param name="value">When this method returns, the value associated with the specified key, if the key is found; otherwise, the default value for the type of the <paramref name="value"/> parameter. This parameter is passed uninitialized.</param><exception cref="T:System.ArgumentNullException"><paramref name="key"/> is null.</exception>
public virtual bool TryGetValue(TKey key, out TValue value)
{
return wrappedDictionary.TryGetValue(key, out value);
}
/// <summary>
/// Gets an <see cref="T:System.Collections.Generic.ICollection`1"/> containing the values in the <see cref="T:System.Collections.Generic.IDictionary`2"/>.
/// </summary>
/// <returns>
/// An <see cref="T:System.Collections.Generic.ICollection`1"/> containing the values in the object that implements <see cref="T:System.Collections.Generic.IDictionary`2"/>.
/// </returns>
public virtual ICollection<TValue> Values
{
get
{
return wrappedDictionary.Values;
}
}
/// <summary>
/// Gets or sets the element with the specified key.
/// </summary>
/// <returns>
/// The element with the specified key.
/// </returns>
/// <param name="key">The key of the element to get or set.</param><exception cref="T:System.ArgumentNullException"><paramref name="key"/> is null.</exception><exception cref="T:System.Collections.Generic.KeyNotFoundException">The property is retrieved and <paramref name="key"/> is not found.</exception><exception cref="T:System.NotSupportedException">The property is set and the <see cref="T:System.Collections.Generic.IDictionary`2"/> is read-only.</exception>
public virtual TValue this[TKey key]
{
get
{
return wrappedDictionary[key];
}
set
{
wrappedDictionary[key] = value;
}
}
/// <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>
public virtual void Add(KeyValuePair<TKey, TValue> item)
{
wrappedDictionary.Add(item);
}
/// <summary>
/// Removes all items from the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <exception cref="T:System.NotSupportedException">The <see cref="T:System.Collections.Generic.ICollection`1"/> is read-only. </exception>
public virtual void Clear()
{
wrappedDictionary.Clear();
}
/// <summary>
/// Determines whether the <see cref="T:System.Collections.Generic.ICollection`1"/> contains a specific value.
/// </summary>
/// <returns>
/// true if <paramref name="item"/> is found in the <see cref="T:System.Collections.Generic.ICollection`1"/>; otherwise, false.
/// </returns>
/// <param name="item">The object to locate in the <see cref="T:System.Collections.Generic.ICollection`1"/>.</param>
public virtual bool Contains(KeyValuePair<TKey, TValue> item)
{
return wrappedDictionary.Contains(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">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"/>.</exception>
public virtual void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
wrappedDictionary.CopyTo(array, arrayIndex);
}
/// <summary>
/// Gets the number of elements contained in the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </summary>
/// <returns>
/// The number of elements contained in the <see cref="T:System.Collections.Generic.ICollection`1"/>.
/// </returns>
public virtual int Count
{
get
{
return wrappedDictionary.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 virtual bool IsReadOnly
{
get { return wrappedDictionary.IsReadOnly; }
}
/// <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 virtual bool Remove(KeyValuePair<TKey, TValue> item)
{
return wrappedDictionary.Remove(item);
}
/// <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>
/// <filterpriority>1</filterpriority>
public virtual IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
return wrappedDictionary.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>
/// <filterpriority>2</filterpriority>
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
我的用例是能够运行相同的代码来操作DataTable和kendo数据源结果，即IDictionary。因此，我使用自定义IDictionary包装了DataTable，以便在DataRow上对IDictionary进行更新。也许有人会发现它很有用，应该作为一个示例实现。
public class DataRowDictionaryWrapper : VirtualDictionary<string, object>
{
private DataRow row;
public DataRowDictionaryWrapper(DataRow row)
{
this.row = row;
this.wrappedDictionary = row.Table.Columns.Cast<DataColumn>().ToDictionary(key => key.ColumnName, c => row[c]);
}
public override void Add(string key, object value)
{
DataColumn col = row.Table.Columns[key];
if (col == null)
{
col = new DataColumn(key);
row.Table.Columns.Add(col);
}
row[col] = value;
base[key] = value;
}
}
public class DataTableDictionaryWrapper : IEnumerable<IDictionary<string, object>>
{
private DataTable dt;
public DataTableDictionaryWrapper(DataTable dt)
{
this.dt = dt;
}
public IEnumerator<IDictionary<string, object>> GetEnumerator()
{
foreach (DataRow row in dt.Rows)
{
yield return new DataRowDictionaryWrapper(row);
}
}
System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator()
{
return this.GetEnumerator();
}
}
答案 2 :(得分：3)
使用“new”关键字实际上更简单。当我的对象包含它们自己唯一的ID值时，我经常这样做。
// Warning Air Code - Subject to bonehead mistakes
internal class SomeDict : Dictionary<myKeyType, myObjectType>
{
public new void Add(myKeyType key, myObjectType value)
{
this.Add(value);
}
internal void Add(myObjectType value)
{
base.Add(value.Id, value);
}
}
答案 3 :(得分：0)
另一个“快速而肮脏”的修复
如果您需要为Add方法添加一些额外的逻辑，您可以创建自己的方法，签名略有不同，并在代码中使用THAT。
public class MyOwnDictionary<TKey, TValue>: Dictionary<TKey, TValue>
{
public void AddPlus(TKey key, TValue value)
{
//some custom logic here
base.Add(key,value);
}
}
（但这会导致维护困难）
答案 4 :(得分：0)
在某些情况下，TKey是TValue的属性，您可能需要考虑使用KeyedCollection<TKey, TValue>，它允许您覆盖 {{1 }}，InsertItem，SetItem和RemoveItem。
它在内部使用字典（除非通过threshold构造函数参数另外指定），而且还管理集合。
我还没有基准测试或比较过性能，可能会有性能差异，因此请谨慎使用。
考虑对.NET Core存储库中的this功能建议进行投票。