Dictionary<TKey,TValue>.IDictionary.Keys 属性

定义

命名空间:

System.Collections.Generic

程序集:

System.Collections.dll

Source:

Dictionary.cs

获取包含 ICollection 的键的 IDictionary。

property System::Collections::ICollection ^ System::Collections::IDictionary::Keys { System::Collections::ICollection ^ get(); };

System.Collections.ICollection System.Collections.IDictionary.Keys { get; }

member this.System.Collections.IDictionary.Keys : System.Collections.ICollection

 ReadOnly Property Keys As ICollection Implements IDictionary.Keys

属性值

ICollection

一个 ICollection，包含 IDictionary 的键。

实现

Keys

示例

下面的代码示例演示如何将 IDictionary.Keys 接口的 System.Collections.IDictionary 属性与 一起使用 Dictionary<TKey,TValue>，以列出字典中的键。 该示例还演示如何枚举字典中的键/值对;请注意，接口的 System.Collections.IDictionary 枚举器返回 DictionaryEntry 对象而不是 KeyValuePair<TKey,TValue> 对象。

该代码示例是为 方法提供的更大示例（包括输出）的一 IDictionary.Add 部分。

using System;
using System.Collections;
using System.Collections.Generic;

public class Example
{
    public static void Main()
    {
        // Create a new dictionary of strings, with string keys,
        // and access it using the IDictionary interface.
        //
        IDictionary openWith = new Dictionary<string, string>();

        // Add some elements to the dictionary. There are no
        // duplicate keys, but some of the values are duplicates.
        // IDictionary.Add throws an exception if incorrect types
        // are supplied for key or value.
        openWith.Add("txt", "notepad.exe");
        openWith.Add("bmp", "paint.exe");
        openWith.Add("dib", "paint.exe");
        openWith.Add("rtf", "wordpad.exe");

Imports System.Collections
Imports System.Collections.Generic

Public Class Example
    
    Public Shared Sub Main() 

        ' Create a new dictionary of strings, with string keys,
        ' and access it using the IDictionary interface.
        '
        Dim openWith As IDictionary = _
            New Dictionary(Of String, String)
        
        ' Add some elements to the dictionary. There are no 
        ' duplicate keys, but some of the values are duplicates.
        ' IDictionary.Add throws an exception if incorrect types
        ' are supplied for key or value.
        openWith.Add("txt", "notepad.exe")
        openWith.Add("bmp", "paint.exe")
        openWith.Add("dib", "paint.exe")
        openWith.Add("rtf", "wordpad.exe")

// To get the keys alone, use the Keys property.
icoll = openWith.Keys;

// The elements of the collection are strongly typed
// with the type that was specified for dictionary keys,
// even though the ICollection interface is not strongly
// typed.
Console.WriteLine();
foreach( string s in icoll )
{
    Console.WriteLine("Key = {0}", s);
}

' To get the keys alone, use the Keys property.
icoll = openWith.Keys

' The elements of the collection are strongly typed
' with the type that was specified for dictionary keys,
' even though the ICollection interface is not strongly
' typed.
Console.WriteLine()
For Each s As String In  icoll
    Console.WriteLine("Key = {0}", s)
Next s

// When you use foreach to enumerate dictionary elements
// with the IDictionary interface, the elements are retrieved
// as DictionaryEntry objects instead of KeyValuePair objects.
Console.WriteLine();
foreach( DictionaryEntry de in openWith )
{
    Console.WriteLine("Key = {0}, Value = {1}",
        de.Key, de.Value);
}

' When you use foreach to enumerate dictionary elements
' with the IDictionary interface, the elements are retrieved
' as DictionaryEntry objects instead of KeyValuePair objects.
Console.WriteLine()
For Each de As DictionaryEntry In openWith
    Console.WriteLine("Key = {0}, Value = {1}", _
        de.Key, de.Value)
Next

    }
}

    End Sub

End Class

注解

返回ICollection的 中键的顺序未指定，但保证其顺序与 属性返回Values的 中的ICollection相应值相同。

获取此属性的值是 O (1) 操作。

另请参阅

• ICollection