Hashtable.Add(Object, Object) Método

Definição

Adiciona um elemento com a chave e o valor especificados ao Hashtable.Adds an element with the specified key and value into the Hashtable.

public:
 virtual void Add(System::Object ^ key, System::Object ^ value);
public virtual void Add (object key, object value);
public virtual void Add (object key, object? value);
abstract member Add : obj * obj -> unit
override this.Add : obj * obj -> unit
Public Overridable Sub Add (key As Object, value As Object)

Parâmetros

key
Object

A chave do elemento a ser adicionada.The key of the element to add.

value
Object

O valor do elemento a ser adicionado.The value of the element to add. O valor pode ser null.The value can be null.

Implementações

Exceções

key é null.key is null.

Já existe um elemento com a mesma chave no Hashtable.An element with the same key already exists in the Hashtable.

O Hashtable é somente leitura.The Hashtable is read-only.

- ou --or- O Hashtable tem um tamanho fixo.The Hashtable has a fixed size.

Exemplos

O exemplo a seguir mostra como adicionar elementos ao Hashtable .The following example shows how to add elements to the Hashtable.

using namespace System;
using namespace System::Collections;
void PrintKeysAndValues( Hashtable^ myHT );
int main()
{
   
   // Creates and initializes a new Hashtable.
   Hashtable^ myHT = gcnew Hashtable;
   myHT->Add( "one", "The" );
   myHT->Add( "two", "quick" );
   myHT->Add( "three", "brown" );
   myHT->Add( "four", "fox" );
   
   // Displays the Hashtable.
   Console::WriteLine( "The Hashtable contains the following:" );
   PrintKeysAndValues( myHT );
}

void PrintKeysAndValues( Hashtable^ myHT )
{
   Console::WriteLine( "\t-KEY-\t-VALUE-" );
   IEnumerator^ myEnum = myHT->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      DictionaryEntry de = *safe_cast<DictionaryEntry ^>(myEnum->Current);
      Console::WriteLine( "\t{0}:\t{1}", de.Key, de.Value );
   }

   Console::WriteLine();
}

/* 
 This code produces the following output.
 
 The Hashtable contains the following:
         -KEY-   -VALUE-
         two:    quick
         three:  brown
         four:   fox
         one:    The
 */
using System;
using System.Collections;
public class SamplesHashtable
{

   public static void Main()
   {
      // Creates and initializes a new Hashtable.
      var myHT = new Hashtable();
      myHT.Add("one", "The");
      myHT.Add("two", "quick");
      myHT.Add("three", "brown");
      myHT.Add("four", "fox");

      // Displays the Hashtable.
      Console.WriteLine("The Hashtable contains the following:");
      PrintKeysAndValues(myHT);
   }

   public static void PrintKeysAndValues( Hashtable myHT )
   {
      Console.WriteLine("\t-KEY-\t-VALUE-");
      foreach (DictionaryEntry de in myHT)
         Console.WriteLine($"\t{de.Key}:\t{de.Value}");
      Console.WriteLine();
   }
}
/*
This code produces the following output.

The Hashtable contains the following:
        -KEY-   -VALUE-
        two:    quick
        three:  brown
        four:   fox
        one:    The
*/
Imports System.Collections

Public Class SamplesHashtable

    Public Shared Sub Main()

        ' Creates and initializes a new Hashtable.
        Dim myHT As New Hashtable()
        myHT.Add("one", "The")
        myHT.Add("two", "quick")
        myHT.Add("three", "brown")
        myHT.Add("four", "fox")

        ' Displays the Hashtable.
        Console.WriteLine("The Hashtable contains the following:")
        PrintKeysAndValues(myHT)

    End Sub

    Public Shared Sub PrintKeysAndValues(myHT As Hashtable)
        Console.WriteLine(vbTab + "-KEY-" + vbTab + "-VALUE-")
        For Each de As DictionaryEntry In myHT
            Console.WriteLine(vbTab + "{0}:" + vbTab + "{1}", de.Key, de.Value)
        Next
        Console.WriteLine()
    End Sub

End Class


' This code produces the following output.
' 
' The Hashtable contains the following:
'         -KEY-   -VALUE-
'         two:    quick
'         one:    The
'         three:  brown
'         four:   fox
' 

Comentários

Uma chave não pode ser null , mas um valor pode ser.A key cannot be null, but a value can be.

Um objeto que não tem nenhuma correlação entre seu estado e seu valor de código hash normalmente não deve ser usado como a chave.An object that has no correlation between its state and its hash code value should typically not be used as the key. Por exemplo, objetos de cadeia de caracteres são melhores que objetos StringBuilder para uso como chaves.For example, String objects are better than StringBuilder objects for use as keys.

Você também pode usar a Item[] propriedade para adicionar novos elementos definindo o valor de uma chave que não existe no Hashtable ; por exemplo, myCollection["myNonexistentKey"] = myValue .You can also use the Item[] property to add new elements by setting the value of a key that does not exist in the Hashtable; for example, myCollection["myNonexistentKey"] = myValue. No entanto, se a chave especificada já existir no Hashtable , definir a Item[] Propriedade substituirá o valor antigo.However, if the specified key already exists in the Hashtable, setting the Item[] property overwrites the old value. Por outro lado, o Add método não modifica os elementos existentes.In contrast, the Add method does not modify existing elements.

Se Count for menor que a capacidade do Hashtable , esse método será uma O(1) operação.If Count is less than the capacity of the Hashtable, this method is an O(1) operation. Se a capacidade precisar ser aumentada para acomodar o novo elemento, esse método se tornará uma O(n) operação, onde n é Count .If the capacity needs to be increased to accommodate the new element, this method becomes an O(n) operation, where n is Count.

Aplica-se a

Confira também