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

 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

Valori restituiti

true IDictionary se contiene un elemento con la chiave specificata; in caso contrario, false.

Implementazioni

Eccezioni

Esempio

Nell'esempio di codice seguente viene illustrato come usare il IDictionary.Contains metodo dell'interfaccia System.Collections.IDictionary con un oggetto Dictionary<TKey,TValue>. Nell'esempio viene illustrato che il metodo restituisce false se viene fornita una chiave del tipo di dati errato.

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");

        // 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": {openWith["ht"]}""");
        }

        // IDictionary.Contains returns false if the wrong data
        // type is supplied.
        Console.WriteLine($"openWith.Contains(29.7) returns {openWith.Contains(29.7)}");
    }
}

open System
open System.Collections
open System.Collections.Generic

// Create a new dictionary of strings, with string keys,
// and access it using the IDictionary interface.
let openWith: IDictionary = 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")

// Contains can be used to test keys before inserting
// them.
if openWith.Contains "ht" |> not then
    openWith.Add("ht", "hypertrm.exe")
    printfn $"""Value added for key = "ht": {openWith["ht"]}"""

// IDictionary.Contains returns false if the wrong data
// type is supplied.
printfn $"openWith.Contains(29.7) returns {openWith.Contains 29.7}"

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 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 che non è assegnabile al tipo TKey di chiave dell'oggetto Dictionary<TKey,TValue>.

Questo metodo si avvicina a un'operazione O(1).