Dictionary<TKey,TValue>.IDictionary.Contains(Object) 方法
定义
重要
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确定是否 IDictionary 包含带有指定键的元素。
virtual bool System.Collections.IDictionary.Contains(System::Object ^ key) = System::Collections::IDictionary::Contains;bool IDictionary.Contains (object key);abstract member System.Collections.IDictionary.Contains : obj -> bool
override this.System.Collections.IDictionary.Contains : obj -> boolFunction Contains (key As Object) As Boolean Implements IDictionary.Contains参数
- key
- Object
要在 IDictionary 中定位的键。
返回
如果 true 包含具有指定键的元素，则为 IDictionary；否则为 false。
实现
例外
key 为 null。
示例
下面的代码示例演示如何将 接口的 System.Collections.IDictionary 方法与 一IDictionary.Contains起使用Dictionary<TKey,TValue>。 该示例演示如果提供了错误数据类型的键，则方法将返回 false 。
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")
// Contains can be used to test keys before inserting
// them.
if (!openWith.Contains("ht"))
{
openWith.Add("ht", "hypertrm.exe");
Console.WriteLine("Value added for key = \"ht\": {0}",
openWith["ht"]);
}
// IDictionary.Contains returns false if the wrong data
// type is supplied.
Console.WriteLine("openWith.Contains(29.7) returns {0}",
openWith.Contains(29.7));
' Contains can be used to test keys before inserting
' them.
If Not openWith.Contains("ht") Then
openWith.Add("ht", "hypertrm.exe")
Console.WriteLine("Value added for key = ""ht"": {0}", _
openWith("ht"))
End If
' IDictionary.Contains returns False if the wrong data
' type is supplied.
Console.WriteLine("openWith.Contains(29.7) returns {0}", _
openWith.Contains(29.7))
}
}
End Sub
End Class
注解
如果 key 的类型不可分配给 的键类型Dictionary<TKey,TValue>TKey，则此方法返回 false 。
此方法用于处理 O (1) 操作。
