ListDictionary 类

定义

使用单向链接列表实现 IDictionaryImplements IDictionary using a singly linked list. 对于通常包含少于 10 项的集合,建议使用该实现方法。Recommended for collections that typically include fewer than 10 items.

public ref class ListDictionary : System::Collections::IDictionary
[System.Serializable]
public class ListDictionary : System.Collections.IDictionary
type ListDictionary = class
    interface IDictionary
    interface ICollection
    interface IEnumerable
Public Class ListDictionary
Implements IDictionary
继承
ListDictionary
属性
实现

示例

下面的代码示例演示了的多个属性和方法ListDictionaryThe following code example demonstrates several of the properties and methods of ListDictionary.

#using <System.dll>

using namespace System;
using namespace System::Collections;
using namespace System::Collections::Specialized;

void PrintKeysAndValues1( IDictionary^ myCol );
void PrintKeysAndValues2( IDictionary^ myCol );
void PrintKeysAndValues3( ListDictionary^ myCol );

int main()
{
   // Creates and initializes a new ListDictionary.
   ListDictionary^ myCol = gcnew ListDictionary;
   myCol->Add( "Braeburn Apples", "1.49" );
   myCol->Add( "Fuji Apples", "1.29" );
   myCol->Add( "Gala Apples", "1.49" );
   myCol->Add( "Golden Delicious Apples", "1.29" );
   myCol->Add( "Granny Smith Apples", "0.89" );
   myCol->Add( "Red Delicious Apples", "0.99" );

   // Display the contents of the collection using for each. This is the preferred method.
   Console::WriteLine( "Displays the elements using for each:" );
   PrintKeysAndValues1( myCol );

   // Display the contents of the collection using the enumerator.
   Console::WriteLine( "Displays the elements using the IDictionaryEnumerator:" );
   PrintKeysAndValues2( myCol );

   // Display the contents of the collection using the Keys, Values, Count, and Item properties.
   Console::WriteLine( "Displays the elements using the Keys, Values, Count, and Item properties:" );
   PrintKeysAndValues3( myCol );

   // Copies the ListDictionary to an array with DictionaryEntry elements.
   array<DictionaryEntry>^myArr = gcnew array<DictionaryEntry>(myCol->Count);
   myCol->CopyTo( myArr, 0 );

   // Displays the values in the array.
   Console::WriteLine( "Displays the elements in the array:" );
   Console::WriteLine( "   KEY                       VALUE" );
   for ( int i = 0; i < myArr->Length; i++ )
      Console::WriteLine( "   {0,-25} {1}", myArr[ i ].Key, myArr[ i ].Value );
   Console::WriteLine();

   // Searches for a key.
   if ( myCol->Contains( "Kiwis" ) )
      Console::WriteLine( "The collection contains the key \"Kiwis\"." );
   else
      Console::WriteLine( "The collection does not contain the key \"Kiwis\"." );

   Console::WriteLine();

   // Deletes a key.
   myCol->Remove( "Plums" );
   Console::WriteLine( "The collection contains the following elements after removing \"Plums\":" );
   PrintKeysAndValues2( myCol );

   // Clears the entire collection.
   myCol->Clear();
   Console::WriteLine( "The collection contains the following elements after it is cleared:" );
   PrintKeysAndValues2( myCol );
}

// Uses the for each statement which hides the complexity of the enumerator.
// NOTE: The for each statement is the preferred way of enumerating the contents of a collection.
void PrintKeysAndValues1( IDictionary^ myCol )  {
   Console::WriteLine( "   KEY                       VALUE" );
   for each ( DictionaryEntry^ de in myCol )
      Console::WriteLine( "   {0,-25} {1}", de->Key, de->Value );
   Console::WriteLine();
}

// Uses the enumerator. 
void PrintKeysAndValues2( IDictionary^ myCol )
{
   IDictionaryEnumerator^ myEnumerator = myCol->GetEnumerator();
   Console::WriteLine( "   KEY                       VALUE" );
   while ( myEnumerator->MoveNext() )
      Console::WriteLine( "   {0,-25} {1}", myEnumerator->Key, myEnumerator->Value );
   Console::WriteLine();
}

// Uses the Keys, Values, Count, and Item properties.
void PrintKeysAndValues3( ListDictionary^ myCol )
{
   array<String^>^myKeys = gcnew array<String^>(myCol->Count);
   myCol->Keys->CopyTo( myKeys, 0 );
   Console::WriteLine( "   INDEX KEY                       VALUE" );
   for ( int i = 0; i < myCol->Count; i++ )
      Console::WriteLine( "   {0,-5} {1,-25} {2}", i, myKeys[ i ], myCol[ myKeys[ i ] ] );
   Console::WriteLine();
}

/*
This code produces the following output.

Displays the elements using for each:
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

Displays the elements using the IDictionaryEnumerator:
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

Displays the elements using the Keys, Values, Count, and Item properties:
   INDEX KEY                       VALUE
   0     Braeburn Apples           1.49
   1     Fuji Apples               1.29
   2     Gala Apples               1.49
   3     Golden Delicious Apples   1.29
   4     Granny Smith Apples       0.89
   5     Red Delicious Apples      0.99

Displays the elements in the array:
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

The collection does not contain the key "Kiwis".

The collection contains the following elements after removing "Plums":
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

The collection contains the following elements after it is cleared:
   KEY                       VALUE


*/
using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesListDictionary  {

   public static void Main()  {

      // Creates and initializes a new ListDictionary.
      ListDictionary myCol = new ListDictionary();
      myCol.Add( "Braeburn Apples", "1.49" );
      myCol.Add( "Fuji Apples", "1.29" );
      myCol.Add( "Gala Apples", "1.49" );
      myCol.Add( "Golden Delicious Apples", "1.29" );
      myCol.Add( "Granny Smith Apples", "0.89" );
      myCol.Add( "Red Delicious Apples", "0.99" );

      // Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine( "Displays the elements using foreach:" );
      PrintKeysAndValues1( myCol );

      // Display the contents of the collection using the enumerator.
      Console.WriteLine( "Displays the elements using the IDictionaryEnumerator:" );
      PrintKeysAndValues2( myCol );

      // Display the contents of the collection using the Keys, Values, Count, and Item properties.
      Console.WriteLine( "Displays the elements using the Keys, Values, Count, and Item properties:" );
      PrintKeysAndValues3( myCol );

      // Copies the ListDictionary to an array with DictionaryEntry elements.
      DictionaryEntry[] myArr = new DictionaryEntry[myCol.Count];
      myCol.CopyTo( myArr, 0 );

      // Displays the values in the array.
      Console.WriteLine( "Displays the elements in the array:" );
      Console.WriteLine( "   KEY                       VALUE" );
      for ( int i = 0; i < myArr.Length; i++ )
         Console.WriteLine( "   {0,-25} {1}", myArr[i].Key, myArr[i].Value );
      Console.WriteLine();

      // Searches for a key.
      if ( myCol.Contains( "Kiwis" ) )
         Console.WriteLine( "The collection contains the key \"Kiwis\"." );
      else
         Console.WriteLine( "The collection does not contain the key \"Kiwis\"." );
      Console.WriteLine();

      // Deletes a key.
      myCol.Remove( "Plums" );
      Console.WriteLine( "The collection contains the following elements after removing \"Plums\":" );
      PrintKeysAndValues1( myCol );

      // Clears the entire collection.
      myCol.Clear();
      Console.WriteLine( "The collection contains the following elements after it is cleared:" );
      PrintKeysAndValues1( myCol );

   }

   // Uses the foreach statement which hides the complexity of the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues1( IDictionary myCol )  {
      Console.WriteLine( "   KEY                       VALUE" );
      foreach ( DictionaryEntry de in myCol )
         Console.WriteLine( "   {0,-25} {1}", de.Key, de.Value );
      Console.WriteLine();
   }

   // Uses the enumerator. 
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues2( IDictionary myCol )  {
      IDictionaryEnumerator myEnumerator = myCol.GetEnumerator();
      Console.WriteLine( "   KEY                       VALUE" );
      while ( myEnumerator.MoveNext() )
         Console.WriteLine( "   {0,-25} {1}", myEnumerator.Key, myEnumerator.Value );
      Console.WriteLine();
   }

   // Uses the Keys, Values, Count, and Item properties.
   public static void PrintKeysAndValues3( ListDictionary myCol )  {
      String[] myKeys = new String[myCol.Count];
      myCol.Keys.CopyTo( myKeys, 0 );

      Console.WriteLine( "   INDEX KEY                       VALUE" );
      for ( int i = 0; i < myCol.Count; i++ )
         Console.WriteLine( "   {0,-5} {1,-25} {2}", i, myKeys[i], myCol[myKeys[i]] );
      Console.WriteLine();
   }

}

/*
This code produces output similar to the following.
Note that because a dictionary is implemented for fast keyed access the order
of the items in the dictionary are not gauranteed and, as a result, should not
be depended on.

Displays the elements using foreach:
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

Displays the elements using the IDictionaryEnumerator:
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

Displays the elements using the Keys, Values, Count, and Item properties:
   INDEX KEY                       VALUE
   0     Braeburn Apples           1.49
   1     Fuji Apples               1.29
   2     Gala Apples               1.49
   3     Golden Delicious Apples   1.29
   4     Granny Smith Apples       0.89
   5     Red Delicious Apples      0.99

Displays the elements in the array:
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

The collection does not contain the key "Kiwis".

The collection contains the following elements after removing "Plums":
   KEY                       VALUE
   Braeburn Apples           1.49
   Fuji Apples               1.29
   Gala Apples               1.49
   Golden Delicious Apples   1.29
   Granny Smith Apples       0.89
   Red Delicious Apples      0.99

The collection contains the following elements after it is cleared:
   KEY                       VALUE


*/
Imports System.Collections
Imports System.Collections.Specialized

Public Class SamplesListDictionary   

   Public Shared Sub Main()

      ' Creates and initializes a new ListDictionary.
      Dim myCol As New ListDictionary()
      myCol.Add("Braeburn Apples", "1.49")
      myCol.Add("Fuji Apples", "1.29")
      myCol.Add("Gala Apples", "1.49")
      myCol.Add("Golden Delicious Apples", "1.29")
      myCol.Add("Granny Smith Apples", "0.89")
      myCol.Add("Red Delicious Apples", "0.99")

      ' Display the contents of the collection using For Each. This is the preferred method.
      Console.WriteLine("Displays the elements using For Each:")
      PrintKeysAndValues(myCol)

      ' Display the contents of the collection using the enumerator.
      Console.WriteLine("Displays the elements using the IDictionaryEnumerator:")
      PrintKeysAndValues2(myCol)

      ' Display the contents of the collection using the Keys, Values, Count, and Item properties.
      Console.WriteLine("Displays the elements using the Keys, Values, Count, and Item properties:")
      PrintKeysAndValues3(myCol)

      ' Copies the ListDictionary to an array with DictionaryEntry elements.
      Dim myArr(myCol.Count) As DictionaryEntry
      myCol.CopyTo(myArr, 0)

      ' Displays the values in the array.
      Console.WriteLine("Displays the elements in the array:")
      Console.WriteLine("   KEY                       VALUE")
      Dim i As Integer
      For i = 0 To myArr.Length - 1
         Console.WriteLine("   {0,-25} {1}", myArr(i).Key, myArr(i).Value)
      Next i
      Console.WriteLine()

      ' Searches for a key.
      If myCol.Contains("Kiwis") Then
         Console.WriteLine("The collection contains the key ""Kiwis"".")
      Else
         Console.WriteLine("The collection does not contain the key ""Kiwis"".")
      End If
      Console.WriteLine()

      ' Deletes a key.
      myCol.Remove("Plums")
      Console.WriteLine("The collection contains the following elements after removing ""Plums"":")
      PrintKeysAndValues(myCol)

      ' Clears the entire collection.
      myCol.Clear()
      Console.WriteLine("The collection contains the following elements after it is cleared:")
      PrintKeysAndValues(myCol)

   End Sub


   ' Uses the For Each statement which hides the complexity of the enumerator.
   ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
   Public Shared Sub PrintKeysAndValues(myCol As IDictionary)

      Console.WriteLine("   KEY                       VALUE")
      Dim de As DictionaryEntry
      For Each de In  myCol
         Console.WriteLine("   {0,-25} {1}", de.Key, de.Value)
      Next de
      Console.WriteLine()

   End Sub


   ' Uses the enumerator. 
   ' NOTE: The For Each statement is the preferred way of enumerating the contents of a collection.
   Public Shared Sub PrintKeysAndValues2(myCol As IDictionary)
      Dim myEnumerator As IDictionaryEnumerator = myCol.GetEnumerator()

      Console.WriteLine("   KEY                       VALUE")
      While myEnumerator.MoveNext()
         Console.WriteLine("   {0,-25} {1}", myEnumerator.Key, myEnumerator.Value)
      End While
      Console.WriteLine()

   End Sub


   ' Uses the Keys, Values, Count, and Item properties.
   Public Shared Sub PrintKeysAndValues3(myCol As ListDictionary)
      Dim myKeys(myCol.Count) As [String]
      myCol.Keys.CopyTo(myKeys, 0)

      Console.WriteLine("   INDEX KEY                       VALUE")
      Dim i As Integer
      For i = 0 To myCol.Count - 1
         Console.WriteLine("   {0,-5} {1,-25} {2}", i, myKeys(i), myCol(myKeys(i)))
      Next i
      Console.WriteLine()

   End Sub

End Class


'This code produces the following output.
'Note that because a dictionary is implemented for fast keyed access the order
'of the items in the dictionary are not gauranteed and, as a result, should not
'be depended on.
'
'Displays the elements using for each:
'   KEY                       VALUE
'   Braeburn Apples           1.49
'   Fuji Apples               1.29
'   Gala Apples               1.49
'   Golden Delicious Apples   1.29
'   Granny Smith Apples       0.89
'   Red Delicious Apples      0.99
'
'Displays the elements using the IDictionaryEnumerator:
'   KEY                       VALUE
'   Braeburn Apples           1.49
'   Fuji Apples               1.29
'   Gala Apples               1.49
'   Golden Delicious Apples   1.29
'   Granny Smith Apples       0.89
'   Red Delicious Apples      0.99
'
'Displays the elements using the Keys, Values, Count, and Item properties:
'   INDEX KEY                       VALUE
'   0     Braeburn Apples           1.49
'   1     Fuji Apples               1.29
'   2     Gala Apples               1.49
'   3     Golden Delicious Apples   1.29
'   4     Granny Smith Apples       0.89
'   5     Red Delicious Apples      0.99
'
'Displays the elements in the array:
'   KEY                       VALUE
'   Braeburn Apples           1.49
'   Fuji Apples               1.29
'   Gala Apples               1.49
'   Golden Delicious Apples   1.29
'   Granny Smith Apples       0.89
'   Red Delicious Apples      0.99
'
'The collection does not contain the key "Kiwis".
'
'The collection contains the following elements after removing "Plums":
'   KEY                       VALUE
'   Braeburn Apples           1.49
'   Fuji Apples               1.29
'   Gala Apples               1.49
'   Golden Delicious Apples   1.29
'   Granny Smith Apples       0.89
'   Red Delicious Apples      0.99
'
'The collection contains the following elements after it is cleared:
'   KEY                       VALUE
'

注解

这是IDictionary使用单向链接列表的简单实现。This is a simple implementation of IDictionary using a singly linked list. 如果元素数小于或等于 10 Hashtable , 则它比 a 更小且更快。It is smaller and faster than a Hashtable if the number of elements is 10 or less. 如果性能对大量元素很重要, 则不应使用此值。This should not be used if performance is important for large numbers of elements.

中的ListDictionary项没有任何保证顺序; 代码不应依赖于当前顺序。Items in a ListDictionary are not in any guaranteed order; code should not depend on the current order. ListDictionary实现以实现快速键控检索; 项的实际内部顺序是依赖实现的, 并且可能在未来版本的产品中发生更改。The ListDictionary is implemented for fast keyed retrieval; the actual internal order of items is implementation-dependent and could change in future versions of the product.

成员Item[Object]( CountAddn、、和Contains ) 是 O () 运算, 其中n是。 RemoveMembers, such as Item[Object], Add, Remove, and Contains are O(n) operations, where n is Count.

键不能为null, 但值可以为。A key cannot be null, but a value can.

语言的for each语句 (在 Visual Basic 中) 返回集合中元素的类型的对象。 foreach C#The foreach statement of the C# language (for each in Visual Basic) returns an object of the type of the elements in the collection. 由于的ListDictionary每个元素都是键/值对, 因此元素类型不是键的类型或值的类型。Since each element of the ListDictionary is a key/value pair, the element type is not the type of the key or the type of the value. 相反, 元素类型为DictionaryEntryInstead, the element type is DictionaryEntry. 例如:For example:

for each (DictionaryEntry de in myListDictionary)
{
    //...
}
foreach (DictionaryEntry de in myListDictionary)
{
    //...
}
For Each de As DictionaryEntry In myListDictionary
    '...
Next de

foreach语句是枚举器周围的包装器, 它仅允许从集合读取, 而不是写入到集合中。The foreach statement is a wrapper around the enumerator, which only allows reading from, not writing to, the collection.

构造函数

ListDictionary()

使用默认比较器创建空白 ListDictionaryCreates an empty ListDictionary using the default comparer.

ListDictionary(IComparer)

使用指定比较器创建空白 ListDictionaryCreates an empty ListDictionary using the specified comparer.

属性

Count

获取包含在 ListDictionary 中的键/值对的数目。Gets the number of key/value pairs contained in the ListDictionary.

IsFixedSize

获取一个值,该值指示 ListDictionary 是否具有固定大小。Gets a value indicating whether the ListDictionary has a fixed size.

IsReadOnly

获取一个值,该值指示 ListDictionary 是否为只读。Gets a value indicating whether the ListDictionary is read-only.

IsSynchronized

获取一个值,该值指示 ListDictionary 是否是同步的(线程安全)。Gets a value indicating whether the ListDictionary is synchronized (thread safe).

Item[Object]

获取或设置与指定的键关联的值。Gets or sets the value associated with the specified key.

Keys

获取包含 ICollection 中的键的 ListDictionaryGets an ICollection containing the keys in the ListDictionary.

SyncRoot

获取可用于同步对 ListDictionary 的访问的对象。Gets an object that can be used to synchronize access to the ListDictionary.

Values

获取一个 ICollection,它包含 ListDictionary 中的值。Gets an ICollection containing the values in the ListDictionary.

方法

Add(Object, Object)

将带有指定键和值的条目添加到 ListDictionary 中。Adds an entry with the specified key and value into the ListDictionary.

Clear()

ListDictionary 中移除所有项。Removes all entries from the ListDictionary.

Contains(Object)

确定 ListDictionary 是否包含特定键。Determines whether the ListDictionary contains a specific key.

CopyTo(Array, Int32)

ListDictionary 项复制到位于指定索引处的一维 Array 实例中。Copies the ListDictionary entries to a one-dimensional Array instance at the specified index.

Equals(Object)

确定指定的对象是否等于当前对象。Determines whether the specified object is equal to the current object.

(继承自 Object)
GetEnumerator()

返回循环访问 IDictionaryEnumeratorListDictionaryReturns an IDictionaryEnumerator that iterates through the ListDictionary.

GetHashCode()

用作默认哈希函数。Serves as the default hash function.

(继承自 Object)
GetType()

获取当前实例的 TypeGets the Type of the current instance.

(继承自 Object)
MemberwiseClone()

创建当前 Object 的浅表副本。Creates a shallow copy of the current Object.

(继承自 Object)
Remove(Object)

ListDictionary 中移除带有指定键的项。Removes the entry with the specified key from the ListDictionary.

ToString()

返回一个表示当前对象的 string。Returns a string that represents the current object.

(继承自 Object)

显式界面实现

IEnumerable.GetEnumerator()

返回循环访问 IEnumeratorListDictionaryReturns an IEnumerator that iterates through the ListDictionary.

扩展方法

Cast<TResult>(IEnumerable)

IEnumerable 的元素强制转换为指定的类型。Casts the elements of an IEnumerable to the specified type.

OfType<TResult>(IEnumerable)

根据指定类型筛选 IEnumerable 的元素。Filters the elements of an IEnumerable based on a specified type.

AsParallel(IEnumerable)

启用查询的并行化。Enables parallelization of a query.

AsQueryable(IEnumerable)

IEnumerable 转换为 IQueryableConverts an IEnumerable to an IQueryable.

适用于

线程安全性

此类型的Shared公共静态 (在 Visual Basic) 成员是线程安全的。Public static (Shared in Visual Basic) members of this type are thread safe. 但不保证所有实例成员都是线程安全的。Any instance members are not guaranteed to be thread safe.

此实现不提供的同步 (线程安全) 包装ListDictionary器, 但派生类可以使用SyncRoot属性创建其自身的ListDictionary同步版本。This implementation does not provide a synchronized (thread safe) wrapper for a ListDictionary, but derived classes can create their own synchronized versions of the ListDictionary using the SyncRoot property.

枚举整个集合本质上不是一个线程安全的过程。Enumerating through a collection is intrinsically not a thread-safe procedure. 即使某个集合已同步,其他线程仍可以修改该集合,这会导致枚举数引发异常。Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. 若要确保枚举过程中的线程安全性,可以在整个枚举期间锁定集合,或者捕获由其他线程进行的更改所导致的异常。To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

另请参阅