Dictionary<TKey,TValue>.IDictionary.Contains(Object) Dictionary<TKey,TValue>.IDictionary.Contains(Object) Dictionary<TKey,TValue>.IDictionary.Contains(Object) Method

定义

确定是否 IDictionary 包含带有指定键的元素。Determines whether the IDictionary contains an element with the specified key.

 virtual bool System.Collections.IDictionary.Contains(System::Object ^ key) = System::Collections::IDictionary::Contains;
bool IDictionary.Contains (object key);
Function Contains (key As Object) As Boolean Implements IDictionary.Contains

参数

key
Object Object Object

要在 IDictionary 中定位的键。The key to locate in the IDictionary.

返回

如果 true 包含具有指定键的元素,则为 IDictionary;否则为 falsetrue if the IDictionary contains an element with the specified key; otherwise, false.

实现

异常

示例

下面的代码示例演示如何将IDictionary.Contains System.Collections.IDictionary接口的方法与结合Dictionary<TKey,TValue>使用。The following code example shows how to use the IDictionary.Contains method of the System.Collections.IDictionary interface with a Dictionary<TKey,TValue>. 该示例演示当提供错误数据false类型的键时,该方法返回。The example demonstrates that the method returns false if a key of the wrong data type is supplied.

此代码示例摘自为IDictionary.Add方法提供的更大示例,包括输出。The code example is part of a larger example, including output, provided for the IDictionary.Add method.

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false TKey Dictionary<TKey,TValue>的类型不能分配给的键类型,则此方法返回。 keyThis method returns false if key is of a type that is not assignable to the key type TKey of the Dictionary<TKey,TValue>.

此方法使用 O (1)操作。This method approaches an O(1) operation.

适用于