从IDictionary转换为通用IDictionary的最佳方法
从IDictionary转换为通用IDictionary的最佳方法
提问于 2010-06-03 06:13:28
我有一个IDictionary字段，我想要通过IDictionary<string, dynamic>类型的属性公开它，转换非常困难，因为我不知道我可以将IDictionary转换成什么。
我能想到的最好的：
IDictionary properties;
protected virtual IDictionary<string, dynamic> Properties {
get {
return _properties.Keys.Cast<string>()
.ToDictionary(name=>name, name=> _properties[name] as dynamic);
}
}回答 4
Stack Overflow用户
回答已采纳
发布于 2010-06-03 06:18:00
如果IDictionary的基础类型不实现IDictionary<string, dynamic>，则不能强制转换对象period。如果是这样的话，通过(IDictionary<string, dynamic>)localVar进行简单的强制转换就足够了。
如果不是，你可以做两件事：
- 将
IDictionary复制到您的泛型类型。 - 构建一个Adapter类，该类将
IDictionary作为依赖项接受，并实现所需的通用IDictionary，从而将调用从一个映射到另一个。
编辑：您刚刚发布的示例代码将在每次调用时复制字典！稍后我将使用一些建议的代码再次编辑。
选项1
您的示例代码方法作为复制数据的一种方法是可靠的，但是副本应该被缓存，否则您将复制很多次。我建议你把实际的翻译代码放到一个单独的方法中，并在第一次使用它时从你的属性中调用它。例如：
private IDictionary dataLayerProperties;
private IDictionary<string, dynamic> translatedProperties = null;
protected virtual IDictionary<string, dynamic> Properties
{
if(translatedProperties == null)
{
translatedProperties = TranslateDictionary(dataLayerProperties);
}
return translatedProperties;
}
public IDictionary<string, dynamic> TranslateDictionary(IDictionary values)
{
return values.Keys.Cast<string>().ToDictionary(key=>key, key => values[key] as dynamic);
}现在，这种方法有明显的缺点...如果需要刷新dataLayerProperties怎么办？您必须再次将translatedProperties设置为空，依此类推。
选项2
这是我首选的方法。
public class TranslatedDictionary : IDictionary<string, dynamic>
{
private IDictionary Original = null;
public TranslatedDictionary(IDictionary original)
{
Original = original;
}
public ICollection<string> Keys
{
get
{
return Original.Keys.Cast<string>().ToList();
}
}
public dynamic this[string key]
{
get
{
return Original[key] as dynamic;
}
set
{
Original[key] = value;
}
}
// and so forth, for each method of IDictionary<string, dynamic>
}
//elsewhere, using your original property and field names:
Properties = new TranslatedDictionary(properties);现在，这种方法也有明显的缺点，最明显的是Keys (以及IDictionary上返回ICollection的值和其他任何东西)必须为每个调用返回一个新的数组。但这仍然允许使用最灵活的方法，因为它确保数据始终是最新的。
Stack Overflow用户
发布于 2010-06-03 06:18:16
除非IDictionary实例的支持类型已经实现了IDictionary<string,dynamic> (如Dictionary<string,dynamic>)，否则强制转换对您没有任何帮助。Cast<>()方法只在返回IEnumerable<T>值时有用，不支持普通类型转换。
如果以IDictionary<string,dynamic>的形式提供数据很重要，那么为什么不从一开始就将其存储为Dictionary<string,dynamic>呢？
Stack Overflow用户
发布于 2013-04-17 06:43:36
下面是顶部答案中推荐的方法的完整实现。这太大了，不适合作为评论。
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Linq;
/// <summary>
/// The casted dictionary.
/// </summary>
/// <typeparam name="TKey">
/// The key type
/// </typeparam>
/// <typeparam name="TValue">
/// The value type
/// </typeparam>
public class CastedDictionary<TKey, TValue> : IDictionary<TKey, TValue>
{
/// <summary>
/// The original dictionary.
/// </summary>
private readonly IDictionary originalDictionary;
/// <summary>
/// The keys.
/// </summary>
private ICollection<TKey> keys;
/// <summary>
/// The values.
/// </summary>
private ICollection<TValue> values;
/// <summary>
/// Initializes a new instance of the <see cref="CastedDictionary{TKey,TValue}"/> class.
/// </summary>
/// <param name="original">
/// The original.
/// </param>
public CastedDictionary(IDictionary original)
: this()
{
if (original == null)
{
throw new ArgumentNullException("original");
}
this.originalDictionary = original;
}
/// <summary>
/// Prevents a default instance of the <see cref="CastedDictionary{TKey, TValue}"/> class from being created.
/// </summary>
[SuppressMessage("StyleCop.CSharp.DocumentationRules", "SA1642:ConstructorSummaryDocumentationMustBeginWithStandardText", Justification = "Style Cop does not analyze private generic class constructor comments properly")]
private CastedDictionary()
{
}
/// <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 int Count
{
get
{
return this.originalDictionary.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 this.originalDictionary.IsReadOnly;
}
}
/// <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 ICollection<TKey> Keys
{
get
{
return this.keys ?? (this.keys = this.originalDictionary.Keys.Cast<TKey>().ToList());
}
}
/// <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 ICollection<TValue> Values
{
get
{
return this.values ?? (this.values = this.originalDictionary.Values.Cast<TValue>().ToList());
}
}
/// <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 TValue this[TKey key]
{
get
{
return (TValue)this.originalDictionary[key];
}
set
{
this.originalDictionary[key] = value;
}
}
/// <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 IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
{
return this.originalDictionary.Cast<KeyValuePair<TKey, TValue>>().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 this.GetEnumerator();
}
/// <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 void Add(KeyValuePair<TKey, TValue> item)
{
this.originalDictionary.Add(item.Key, item.Value);
}
/// <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 void Clear()
{
this.originalDictionary.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 bool Contains(KeyValuePair<TKey, TValue> item)
{
return this.originalDictionary.Contains(item.Key) && EqualityComparer<TValue>.Default.Equals(this[item.Key], item.Value);
}
/// <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 void CopyTo(KeyValuePair<TKey, TValue>[] array, int arrayIndex)
{
this.originalDictionary.CopyTo(array, arrayIndex);
}
/// <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(KeyValuePair<TKey, TValue> item)
{
if (this.Contains(item))
{
this.originalDictionary.Remove(item.Key);
return true;
}
return false;
}
/// <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 bool ContainsKey(TKey key)
{
return this.originalDictionary.Contains(key);
}
/// <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 void Add(TKey key, TValue value)
{
this.originalDictionary.Add(key, value);
}
/// <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 bool Remove(TKey key)
{
if (this.ContainsKey(key))
{
this.originalDictionary.Remove(key);
return true;
}
return false;
}
/// <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 bool TryGetValue(TKey key, out TValue value)
{
// ReSharper disable CompareNonConstrainedGenericWithNull
if (typeof(TKey).IsValueType == false && key == null)
// ReSharper restore CompareNonConstrainedGenericWithNull
{
throw new ArgumentNullException("key");
}
if (this.ContainsKey(key))
{
value = this[key];
return true;
}
value = default(TValue);
return false;
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/2962011
复制相关文章
相似问题
腾讯云开发者
