我在只读属性中返回对字典的引用.如何防止消费者更改我的数据？如果这是IList，我可以简单地把它退回AsReadOnly.有没有类似的东西我可以用字典来做？
Private _mydictionary As Dictionary(Of String, String)
Public ReadOnly Property MyDictionary() As Dictionary(Of String, String)
Get
Return _mydictionary
End Get
End Property
下面是一个包装字典的简单实现:
public class ReadOnlyDictionary<TKey, TValue> : IDictionary<TKey, TValue>
{
private readonly IDictionary<TKey, TValue> _dictionary;
public ReadOnlyDictionary()
{
_dictionary = new Dictionary<TKey, TValue>();
}
public ReadOnlyDictionary(IDictionary<TKey, TValue> dictionary)
{
_dictionary = dictionary;
}
#region IDictionary<TKey,TValue> Members
void IDictionary<TKey, TValue>.Add(TKey key, TValue value)
{
throw ReadOnlyException();
}
public bool ContainsKey(TKey key)
{
return _dictionary.ContainsKey(key);
}
public ICollection<TKey> Keys
{
get { return _dictionary.Keys; }
}
bool IDictionary<TKey, TValue>.Remove(TKey key)
{
throw ReadOnlyException();
}
public bool TryGetValue(TKey key, out TValue value)
{
return _dictionary.TryGetValue(key, out value);
}
public ICollection<TValue> Values
{
get { return _dictionary.Values; }
}
public TValue this[TKey key]
{
get
{
return _dictionary[key];
}
}
TValue IDictionary<TKey, TValue>.this[TKey key]
{
get
{
return this[key];
}
set
{
throw ReadOnlyException();
}
}
#endregion
#region ICollection<KeyValuePair<TKey,TValue>> Members
void ICollection<KeyValuePair<TKey, TValue>>.Add(KeyValuePair<TKey, TValue> item)
{
throw ReadOnlyException();
}
void ICollection<KeyValuePair<TKey, TValue>>.Clear()
{
throw ReadOnlyException();
}
public bool Contains(KeyValuePair<TKey, TValue> item)
{
return _dictionary.Contains(item);
}
public void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
_dictionary.CopyTo(array, arrayIndex);
}
public int Count
{
get { return _dictionary.Count; }
}
public bool IsReadOnly
{
get { return true; }
}
bool ICollection<KeyValuePair<TKey, TValue>>.Remove(KeyValuePair<TKey, TValue> item)
{
throw ReadOnlyException();
}
#endregion
#region IEnumerable<KeyValuePair<TKey,TValue>> Members
public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
return _dictionary.GetEnumerator();
}
#endregion
#region IEnumerable Members
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
#endregion
private static Exception ReadOnlyException()
{
return new NotSupportedException("This dictionary is read-only");
}
}