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

Definizione

Determina se IDictionary contiene un elemento con la chiave specificata.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);
abstract member System.Collections.IDictionary.Contains : obj -> bool
override this.System.Collections.IDictionary.Contains : obj -> bool
Function Contains (key As Object) As Boolean Implements IDictionary.Contains

Parametri

key
Object

Chiave da individuare in IDictionary.The key to locate in the IDictionary.

Restituisce

Boolean

true se IDictionary contiene un elemento con la chiave specificata; in caso contrario, false.true if the IDictionary contains an element with the specified key; otherwise, false.

Implementazioni

Eccezioni

key è null.key is null.

Esempio

Nell'esempio di codice seguente viene illustrato come utilizzare il IDictionary.Contains metodo dell' System.Collections.IDictionary interfaccia con un oggetto Dictionary<TKey,TValue> .The following code example shows how to use the IDictionary.Contains method of the System.Collections.IDictionary interface with a Dictionary<TKey,TValue>. Nell'esempio viene illustrato che il metodo restituisce false se viene fornita una chiave con tipo di dati errato.The example demonstrates that the method returns false if a key of the wrong data type is supplied.

L'esempio di codice fa parte di un esempio più ampio, incluso l'output, fornito per il IDictionary.Add metodo.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

Commenti

Questo metodo restituisce false se key è di un tipo non assegnabile al tipo TKey di chiave di Dictionary<TKey,TValue> .This method returns false if key is of a type that is not assignable to the key type TKey of the Dictionary<TKey,TValue>.

Questo metodo si avvicina a un'operazione O (1).This method approaches an O(1) operation.

Si applica a