Dictionary<TKey,TValue>.Keys 属性
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
获得一个包含 Dictionary<TKey,TValue> 中的键的集合。
public:
property System::Collections::Generic::Dictionary<TKey, TValue>::KeyCollection ^ Keys { System::Collections::Generic::Dictionary<TKey, TValue>::KeyCollection ^ get(); };C#
public System.Collections.Generic.Dictionary<TKey,TValue>.KeyCollection Keys { get; }member this.Keys : System.Collections.Generic.Dictionary<'Key, 'Value>.KeyCollectionPublic ReadOnly Property Keys As Dictionary(Of TKey, TValue).KeyCollection一个 Dictionary<TKey,TValue>.KeyCollection，包含 Dictionary<TKey,TValue> 中的键。
下面的代码示例演示如何使用 Keys 属性枚举字典中的键，以及如何枚举字典中的键和值。
此代码是可以编译和执行的较大示例的一部分， (openWith 是此示例中使用的字典的名称) 。 请参阅 Dictionary<TKey,TValue>。
// To get the keys alone, use the Keys property.
Dictionary<String^, String^>::KeyCollection^ keyColl =
openWith->Keys;
// The elements of the KeyCollection are strongly typed
// with the type that was specified for dictionary keys.
Console::WriteLine();
for each( String^ s in keyColl )
{
Console::WriteLine("Key = {0}", s);
}
C#
// To get the keys alone, use the Keys property.
Dictionary<string, string>.KeyCollection keyColl =
openWith.Keys;
// The elements of the KeyCollection are strongly typed
// with the type that was specified for dictionary keys.
Console.WriteLine();
foreach( string s in keyColl )
{
Console.WriteLine("Key = {0}", s);
}
' To get the keys alone, use the Keys property.
Dim keyColl As _
Dictionary(Of String, String).KeyCollection = _
openWith.Keys
' The elements of the KeyCollection are strongly typed
' with the type that was specified for dictionary keys.
Console.WriteLine()
For Each s As String In keyColl
Console.WriteLine("Key = {0}", s)
Next s
// When you use foreach to enumerate dictionary elements,
// the elements are retrieved as KeyValuePair objects.
Console::WriteLine();
for each( KeyValuePair<String^, String^> kvp in openWith )
{
Console::WriteLine("Key = {0}, Value = {1}",
kvp.Key, kvp.Value);
}
C#
// When you use foreach to enumerate dictionary elements,
// the elements are retrieved as KeyValuePair objects.
Console.WriteLine();
foreach( KeyValuePair<string, string> kvp in openWith )
{
Console.WriteLine("Key = {0}, Value = {1}",
kvp.Key, kvp.Value);
}
' When you use foreach to enumerate dictionary elements,
' the elements are retrieved as KeyValuePair objects.
Console.WriteLine()
For Each kvp As KeyValuePair(Of String, String) In openWith
Console.WriteLine("Key = {0}, Value = {1}", _
kvp.Key, kvp.Value)
Next kvp
中Dictionary<TKey,TValue>.KeyCollection键的顺序未指定，但它与 属性返回Values的 中Dictionary<TKey,TValue>.ValueCollection关联值的顺序相同。
返回的 Dictionary<TKey,TValue>.KeyCollection 不是静态副本;相反， Dictionary<TKey,TValue>.KeyCollection 引用回原始 Dictionary<TKey,TValue>中的键。 因此，对 Dictionary<TKey,TValue> 的更改将继续反映在 中 Dictionary<TKey,TValue>.KeyCollection。
获取此属性的值是 O (1) 操作。
| 产品 | 版本 |
|---|---|
| .NET | Core 1.0, Core 1.1, Core 2.0, Core 2.1, Core 2.2, Core 3.0, Core 3.1, 5, 6, 7, 8, 9 |
| .NET Framework | 2.0, 3.0, 3.5, 4.0, 4.5, 4.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, 4.7.2, 4.8, 4.8.1 |
| .NET Standard | 1.0, 1.1, 1.2, 1.3, 1.4, 1.6, 2.0, 2.1 |
| UWP | 10.0 |
